Propagation of Millimeter Waves Through the Atmosphere,
A. B. Crawford and D. C. Hogg

THE COVER: Converging beams of red, blue and green light
produce image for Bell Laboratories’ study of subjective as-
pects in color television. (See opposite page.)

The BELL LABORATORIES RECORD is published monthly by Bell Telephone
Laboratories, Incorporated, 463 West Street, New York 14, N. Y., M. J. KELLY,
President; M. B. LONG, Secretary and Treasurer. Subscriptions: $2.00 per

EDITORIAL BOARD
F, J. Singer, Chairman
J. A. Hornbeck
F. A. Korn
E. T, Mottram
R. J. Nossaman
W.E. Reichle
A. H. White

year; Foreign, $2.60 per year. Checks should be made payable to Bell Labora-
tories Record and addressed to the Circulati Manager. Printed in U. S. A.

EDITORIAL STAFF
G. E. Schindler, Jr., Editor
W. W. Mines, Assistant Editor, Murray Hill
A. G. Tressler, Assistant Editor, Murray Hill
A. B. Hilton, Assistant Editor
R. L. Shepherd, Production Editor
T. N. Pope, Circulation Manager

Color television bears out well the adage, “beauty is in the eye of the be-
holder,” since only the human eye can measure “sharpness.” This purely
subjective quality of video depends on the many complex parameters of a
television system. Because Bell System transmission facilities are frequently
a part of such systems, a color television simulator has been devised at the
Laboratories to help answer some of the basic questions about sharpness.

From time immemorial man has made pictures
in color. Before modern times all pictures were
made by hand, and any faults in form or color could
be attributed to the artist’s lack of skill. As the
scientific understanding of picture-making in-
creased, this better understanding led to the intro-
duction of new techniques. Complete freedom
from hand reproduction became possible about a
century ago, with the invention of photography.
This revolutionary advance brought with it, of
course, new kinds of picture faults that required
increased scientific understanding. Photography
has progressed rapidly — nowadays we make pic-
tures that move, we make them in full color, and
most of us take them quite for granted.

The youngest of the arts of picture-making is
color television. This new art has released us from
some of the limitations imposed by the dyes and
processes used in color photography, but not with-
out cost. The very complexity of television appa-
ratus results in a host of new picture faults to be
understood and overcome.

To increase our understanding of some of these
faults, the Visual and Acoustics Research Depart-
ment at Bell Laboratories has for some time used
a “defocusing” projector. The chief function of this
projector is to make color pictures that are meas-
urably blurred. This unusual research tool can
also produce a full color image that looks like the
picture one might see on a color television receiver.
The blurring that results from out-of-focus projec-
tion can then be used to simulate the blurring that
results when a color television picture is trans-
mitted over a circuit of limited bandwidth.

In the future, the Bell System may be called
upon to transmit television signals which will pro-

duce color pictures sharper than those presently
broadcast for home entertainment. By being able
to simulate such color television pictures right now,
it is possible to study some of the factors which
influence sharpness.

Color television pictures are produced by a three-
color additive process. The picture tube produces
a separate and complete image in each of the pri-
mary colors — red, green and blue — and these three
pictures are superimposed on the screen of the tube.
The controlled addition of three colors at every
point on the screen can produce whatever color is
required at each point to build up a full color
image on the viewing screen.

The defocusing projector, shown in Figure 1,
also makes color pictures by an additive process,

Fig. 1— Front view of the defocusing projector
showing the four individual projector lenses.

Fig. 2— The vertical reference lines on the screen show that these two pictures are the same size.

as a proper simulator should. The projector, or
more accurately, the projection machine, is actually
composed of four projectors, with independent
focusing adjustments, directed at a common pro-
jection screen. The machine projects separate pic-
tures, one in red light, one in green light and one
in blue light onto the screen, where the additive
process takes place. The viewer sees only the sum
of these three pictures, or a full color image. The
fourth projector is available for showing a com-
parison picture if needed.

A basic requirement, when separate images are
projected to make a color picture, is that the sepa-
rate images remain in good register on the screen.
The machine would not be useful for sharpness
studies if the effects of focus adjustment were to
be contaminated by misregistration. In other words,
image size and centering must both remain fixed
while the focus changes.

The optical principle used to maintain constant
magnification with variable focus is a simple one.
Taking an ordinary home slide projector as an ex-
ample, we know that the picture gets larger as
the projector is moved farther from the screen. We
also know that the picture goes in and out of focus
as the lens is moved back and forth on the pro-
jector. Likewise, movement of the lens causes the
picture to change size. If one could move the whole
projector back and at the same time move the lens
forward on the projector by the proper distance,
he could keep the picture from changing size. The
increase in size due to moving the projector back

would cancel out the decrease in size due to moving
the lens forward, yet the picture would go out of
focus. Figure 2 illustrates projections of the same
slide and shows that the two images are exactly the
same size, even though the picture on the right is
obviously out of focus.

To make possible the precise motions and opti-
cal relationships necessary to get a constant-size
picture of variable focus, a well-known mechanism

FIXED MEMBER
Fig. 3 — Pantograph maintains spacing of projector
and lens for in- and out-of-focus projection.

—the pantograph—is used. The pantograph,
which is simply a geometric parallelogram with
pivots at the corners, provides exactly the motions
required. Figure 3 shows how the pantograph was
adapted to this use. The pantographs as they ap-
pear in the simulator are shown in Figure 5. A bel-
lows, seen between the slide carrier and the lens,
accommodates the relative motion of these parts
as the projector moves in its focusing and defocus-
ing action. The bellows stretches about % of an
inch when the whole projector moves back two
inches. The two projectors on the other side are
mounted in the same way.

The four projectors are mounted so that the pro-
jection lenses and lantern slides are all squared
onto, or held parallel to, the screen. The centers
of the lenses are closer together than the centers
of the slides. The resulting projection is known

‘ig. 4 — The observer, E, Averbach, tells the operator, G.
Nielsen, when he thinks the sharpness of this picture
natches that of a comparison picture.

as off-axis projection, because the center of the
image is a few degrees off the optical axis of each
lens. This kind of projection insures perfect regis-
tration of the images on the screen at all times and
eliminates “keystone” distortion — an image irregu-
larity that would result if the projectors were not
squared onto the screen. The keystone effect, to
describe it simply, is the tapered shape a rectangu-
lar picture assumes when projected at an angle. The
slightly tapered keystone shape, which is ordi-
narily not objectionable, would make image regis-
tration impossible. The illuminating systems are
“toed-in” so that they all point toward the center
of the screen to improve the uniformity of coloring
over the field.

Fig. 5— Side view shows top pantograph as it
actually looks in the projection machine.

This machine performs well because all of its
parts have been made and aligned with precision.
The lengths of corresponding sides of the panto-
graphs differ by less than one thousandth of an
inch. The lantern slides and the lenses are squared
onto the screen to better than five minutes of arc.
The in-focus magnifications of the four projectors
are equalized to better than one part in 2,000.
As a result, the separate images on the screen,
whether in sharp focus or not, are in register to
within the limits of unaided vision.

A most important part of this projection machine
is its control system. Each of the four projectors
is actuated by small hydraulic controls which move
the projectors slowly and smoothly and hold them
firmly in position. Small indicating units monitor
the individual projector positions and transmit
these positions to indicator dials mounted on the
control panel.

The indicator dials, in effect, relate the focus
condition of individual projectors to the sharpness
of the color picture on the screen. The sharpness
of a three-color additive picture — a purely subjec-
tive quality — can only be judged by an observer.
In a typical experiment, the observer examines a
picture in the “test condition” (the three pro-
jectors out of focus by different amounts) and then
examines a picture in the “gauging condition” (the
three projectors out of focus by the same amount).
The observer then adjusts the gauging condition
to be equally as sharp as the test condition. Fig-

ure 4 shows the projector as it is used with an
observer. The indicator dial readings called for
by the observer in making this sharpness match are
then recorded by the operators and can be trans-
lated into bandwidth information by a straight-
forward calibration procedure.

Fig. 6 — Equivalent bandwidths of a 10-mc, three-
color picture show the line of maximum sharpness.

A three-dimensional plot of the sharpness-match
data from ten observers, statistically analyzed and
put into terms of bandwidth, is presented in Fig-
ure 6. The percentages of the total band of ten
megacycles allotted to blue and green are shown
on the base plane. Red would, of course, occupy
the remainder of the band. The equivalent band-
width of the gauging picture (all three projectors
focused identically ) is plotted vertically. All of the

points on the vertical, or equivalent-bandwidth,
axis form the top surface of the plot. Wherever
the surface lies above ten megacycles, the color
picture looks sharper than would the picture trans-
mitted by a ten-megacycle band equally appor-
tioned. The maximum sharpness — equivalent to a
15.6-megacycle picture — occurs when 63 per cent
of the total band is allotted to green. In other
words, a ten-megacycle test picture (each pro-
jector out of focus by a different amount) with
6.3 megacycles devoted to green looks just as sharp
as a 15.6-megacycle picture with 5.2 megacycles
devoted to each color. It is also interesting to note
that the remaining 37 per cent of the total band
can be allotted to red and blue in any proportion.

Many experiments of this type have been per-
formed by engineers at the Laboratories and else-
where, some of them earlier than this one, and
they all point toward the same conclusion: tele-
vision in three colors can be made to look just as
sharp as television in monochrome without paying
the price of three times the bandwidth. Such in-
formation is the foundation of the latest system of
color television transmission adopted by the Fed-
eral Communications Commission.

In practical terms, television researchers want
to know whether the color picture sent by one
television system will look sharper than that sent
by another. This color television simulator is help-
ing to fit together some of the pieces of this larger
puzzle. In addition to increasing our understanding
of some of the complex problems involved in the
transmission of color television signals, this pro-
jection machine has also made some valuable con-
tributions in the field of visual acuity in color.

M. W. Ba.pwin, Jr., a native of Portland, Maine, received the E.E. degree
from Cornell in 1925 and the M.A. degree from Columbia in 1928. He joined
Bell Laboratories in 1925, and has been associated with the Research Department
since that time. His primary concern has been television research, with particular
emphasis on subjective aspects. During the war he was involved in the develop-
ment of an automatic tracking anti-aircraft radar. He is a member of Eta Kappa
Nu and of Tau Beta Pi. He is a Fellow of the I.R.E., and is currently Chairman
of its Standards Committee.

Private Branch Exchange (PBX) customers differ widely in their telephone
requirements — some have only a few extensions and others have thousands
of extensions in hotels, department stores, and large industrial establish-
ments. Most businesses, however, require less than sixty extensions, and de-

mand has been increasing for a modern dial PBX system to serve such
customers. The new 756A PBX is a small “packaged” design that matches
the decor of modern offices. In addition to the conventional PBX services,
the 756A provides a “camp-on” feature to permit automatic connection

To most people, a PBX is a telephone switch-
board, frequently located in or near the reception
room of a business establishment and used for
servicing calls over the company’s telephone exten-
sions. In a dial PBX, however, the switchboard is
only one part of the total equipment; much of the
work of interconnecting telephones is done auto-
matically by electromechanical switches. The
switchboard in a dial installation might thus be
considered as a sort of “control panel,” with the
relays, switches, and other equipment out of sight.

In small manual PBX systems, much or even all
of the “behind-the-scenes” equipment can be
mounted within the switchboard itself. On the
other hand, even a small dial system requires
switching equipment and power equipment
mounted in additional cabinets. As a consequence,
the installation of present-day systems occasionally
offers difficulties because a particular building may
have narrow doors, too small an elevator. or in-
sufficient floor bracing. These problems have been
solved by the new 756A crossbar dial PBX devel-
oped at the Laboratories.

Many telephone customers requiring dial PBX
service have between 20 and 60 extension lines and

10 or fewer central-office trunks, and the most
economical arrangement for serving this field is
to provide only one or two “packaged” systems.
The 756A is a small packaged design supplied in
capacities of either 40 or 60 lines and equipped for
6 central-office trunks. Four additional central-office
trunks can be added as desired. The basic switching
components are crossbar switches and wire-spring
relays. The 756A is also the first equipment to use
the recently-developed “2-in-1” wire-spring relay
that provides two relays in the space normally re-
quired for one.

Physically, the entire PBX is housed in two modu-
lar cabinets of steel and aluminum (Figure 1).
The depth and height are similar to those of
standard office filing cabinets, and all maintenance
is done from the front. Each module contains
three small relay racks arranged so that they can
be pulled forward out of the module like vertical
file drawers. Each rack mounts on ball-bearing
telescoping slides, Interlocking latches prevent more
than one rack being pulled out at a time and,
since each weighs aboui the same, the combined
weight of the other two racks is sufficient to keep
the cabinet steady. For this reason there is no

The PBX cabinets are designed for mounting in
regular office space, along with file cabinets or other
office furniture. Since an extended rack projects no
further than a standard file drawer, the aisles do
not need to be widened. The cabinets are of modern
styling, finished in a shade of beige-gray that has
become popular in office furniture. Sound-absorbing
material reduces the noise of the switching equip-
ment. The PBX is connected to the office wiring
by plugs and pre-arranged jacks.

A total of three equipment modules are provided,
from which the twin-module 40-line or 60-line 756A
may be constructed. One module is common to both
40 and 60 lines, and the second contains additional
equipment for either the 40-line or the 60-line sys-
tem. A new modern attendant’s console, shown in the
illustration at the head of this article, has sufficient
capacity to handle all ordinary calls requiring the
assistance of an attendant. This console features
push-button keys and simplified operation. Since
it is assumed that the attendant will have other
duties as a secretary or receptionist, the console is
small enough for table- or desk-top mounting.

Smaller systems may use a six-button telephone
set instead of the console. With some installations
a switchboard may be more desirable than either
the console or the six-button set. In such cases the

The power supply is completely self-contained,
and is mounted in the first or basic module. Com-
mercial 115-volt, 60-cycle ac is stepped down in
voltage, rectified, and filtered to produce 48 volts
de for use in the PBX. The filter contains a large
capacitor that stores sufficient electrical energy to
maintain the voltage during momentary interrup-
tions of the commercial supply. Where interruptions
are apt to be of appreciable length, an additional
modular cabinet can be supplied. This cabinet
contains storage batteries as a reserve power source,
and a rectifier keeps the batteries charged. Ringing
current, signaling tones, and flashing interruptions
are generated by equipment in the power-supply
unit regularly furnished.

While most present-day dial PBX’s use step-by-
step switches, the 756A achieves small size and
faster operation by using crossbar switches and
common-control principles. It operates essentially
as a small crossbar office; register circuits connect
to calling lines and trunks to supply dial tone and
receive called numbers. The called numbers are
passed to a marker which determines the busy and
idle state of called points, performs an idle-hunting
function for grouped lines and trunks, and controls
the establishment of talking connections. The cross-
bar switches establish all connections.

Although only one marker is supplied, it actually
contains two independent marker channels, used
alternately on successive calls. Should trouble be
encountered, the marker “times out” and makes a
second trial using the other channel. The two regis-
ters are also used alternately unless one is busy.
Busy tone is normally supplied by a busy-tone
trunk but, should this trunk itself be busy, the
marker operates a relay in the appropriate register,
and the register supplies busy tone. Troubles are
indicated by lamp displays.

All conventional PBX services are available with
the 756A. Calls to extensions are placed by dialing
two digits; with two to seven as the number in
the initial digit. Calls requiring the attendant are
placed by dialing zero. Dialing an initial 9 causes
connection to an idle central-office trunk and the
calling station line receives a second dial tone
from the central office. Where certain extensions
are restricted from direct outside dialing, users
must dial 0 for the attendant and ask her to get
the number. If they dial 9, they will be intercepted
and transferred to the attendant. Also, certain ex-
tensions, while not restricted from dialing local
outside calls, will also be intercepted if used to dial

Inward calls from a central office first cause
the attendant to be signaled. She answers a trunk
by its key appearance on the console and asks for
the desired called party. She then operates a key
to summon a register which furnishes dial tone,
and then either keys or dials the desired extension
number into the PBX equipment. The trunk is
connected to the desired station which receives
ringing current, and subsequent talking battery
_from the central office. The attendant may split the
‘connection when desired until after conversation
with the called party begins. After the attendant
releases her keys, she may be recalled by the called
party operating his switch-hook momentarily. Dis-
connects take place automatically without involving
the attendant.

A “camp-on” feature has been included in the
756A for inward calls from a central office. If the
called station is busy, the attendant is so notified and
can advise the calling party that he may wait if
he wishes. After the attendant releases from the
call, the trunk will “camp-on” until the line is
free. As soon as the first call disconnects, the trunk
is automatically cut through to the called line and
applies ringing current. No further assistance is
required from the attendant. This feature reduces
waiting time for inward calls to busy lines and
frees the attendant for other duties.

The central office provides talking current for
both inward and outward calls, and also provides
current to ring the PBX attendant on inward calls.
For intra-PBX calls — those between two extensions
—ringing and talking current are supplied by the

Fig. 2— The 756A PBX circuitry being inspected
at the Cleveland, Ohio, trial installation.

trunk, or junctor, is brought in on this type of call
to supply the necessary currents and signals. Out-
ward trunks to other PBX’s are reached by dialing
8, and calls over these trunks are handled in the
same manner as outgoing calls.

This new PBX, modern in design and appearance,
should fill the telephone needs of today’s smaller
businesses. The ease of installation and mainte-
nance, the adaptability of its size and modular
construction to the requirements of modern offices,
and the new features offered should make the
756A system attractive both to customers and to the

PBX. An additional circuit, called an “intercom” Operating Telephone Companies.

O. H. Wiuirorp, whose home town is Greenwood, Miss., joined the Labora-
tories in 1920 and initially engaged in laboratory and field testing of step-by-
step, panel, manual and No. 1 crossbar systems. During World War II, he was
associated with various military projects, and at the close of the war he
became concerned with the development of the No. 5 crossbar system, particu-
larly in the design of the maintenance facilities. He was an active member of the
group representing the Laboratories during the installation and cutover of the
first No. 5 system in Media, Pa. Transferring to the Systems Engineering Depart-
ment, he prepared engineering information on the No. 5 system for the use of
Operating Company engineers in planning central offices. He was active in the
Englewood DDD trial and thereafter in engineering studies related to the ex-
pansion of the customer dialing network. He is now in charge of a Special Systems
Engineering group studying requirements for new PBX features and systems.

A new concept in memory devices has recently
been announced at Bell Laboratories. As a result of
exploratory work by A. H. Bobeck of the Device
Development Department, it may now be possible
to design memory systems that are simpler to fab-
ricate and more economical to manufacture than
existing systems. The new concept, which has been
given the name “Twistor”, may find extensive appli-
cation in computers and electronic switching sys-
tems where rapid-access, high-capacity memories
are necessary.

Set-up for testing magnetic wire: I, supplies cir-
cular field and I, in solenoid supplies longitudinal
field, resulting in helical magnetization of the wire.

A. H. Bobeck tests memory characteristics of a
“Twistor” device, which incor porates magnetic wires.

could be constructed in the familiar grid-like or
coordinate pattern. This is the way present mag-
netic-core memories are arranged — horizontal and
vertical wires are interwoven, with a donut-shaped
magnetic core encircling each intersection. A pulse
of energy along one wire is chosen to be insufficient
for magnetizing a core, but coincident pulses along
both a horizontal and a vertical wire will magnetize
the core in a circular direction. Pulses of opposite
polarity magnetize the core in the reverse direction
around the donut. In this way, one “bit” of informa-
tion is stored at one coordinate point in the array.

A “Twistor” array would be similar in appearance
to the magnetic-core memory, but would have no
cores. It would be constructed merely by interweav-
ing copper wires with wires made of a magnetic
material, much as window screen is woven.

The “Twistor” gets its name from a characteristic
of magnetic wire. Normally, such wire can be mag-
netized most easily in the longitudinal direction (in
a straight line along its length). But if a torsional
force is applied to the wire, the magnetization will
prefer to lie along a helical, rather than longitudinal,
path. Torsion may not have to be applied to the
magnetic wire in a final device. The preference for
helical magnetization may be “frozen” into the wire
during processing.

In a “Twistor” memory, the required helical field
can be obtained by applying coincident pulses of

current through the copper and magnetic wires.
Since current causes a circular magnetic field
around a conductor, the circular component is read-
ily supplied with a pulse of current through the
magnetic wire. The field resulting from current in
the copper conductor is also circular, but at an in-
tersection where the copper wire touches the mag-
netic wire at right angles, this field has a component
longitudinal to the magnetic wire. Thus, to “write”
information into 10 x 10 array, for example, current
could be applied to wire number 7 of 10 vertical
magnetic wires, and to wire number 3 of 10 hori-
zontal copper wires. This would produce helical
magnetization in the magnetic wire in the immedi-
ate vicinity of the (7,3) coordinate point. In this
way, a “bit” of information can be stored in the
“direction” of the helical magnetization.

Although two pulses of current are needed to
“write” information into a “Twistor” memory, only
a single pulse is required for “readout”. The current
is applied to one of the copper wires so that it will
overdrive the longitudinal field in the reverse direc-
tion at any intersection where a bit is stored. A
“readout” pulse of voltage will then be induced in
the associated magnetic wire. Because the lines of
magnetic flux along the helical path “wrap” the
magnetic wire many times, a favorable increase in

output signal is obtained. Thus, the magnetic wire
is used both as the storage medium and as the
sensing element.

Investigations are now under way to determine
optimum size and composition for the magnetic
wires. It appears that a conductor plated with mag-
netic material will be most useful. Diameters as
small as one thousandth of an inch appear to be
usable. At least 10 bits per inch may be stored along
such a magnetic wire without adverse interaction.

In conventional magnetic-core memory devices,
conductors must be threaded through the cores to
make up a suitable matrix. When a ferrite sheet is
used, either a threading or a plating operation is
necessary for suitably locating the conductors. How-
ever, with the “Twistor”, the ferrite material is com-
pletely eliminated and no threading or plating is
necessary. Speed of operation and output are com-
parable to those of ferrite systems.

Present indications are that the drive circuits for
a “Twistor” array can be readily transistorized.
Thus, a memory system using the “Twistor” concept
will retain all of the advantages of ferrite-core or
sheet systems, and will be much simpler and more
economical to fabricate.

An experimental version of the “Twistor” memory: information-storage section in center consists only of
horizontal magnetic wires and vertical copper wires. Magnetic wire serves for both storage and sensing.

To handle air traffic in the vicinity of air bases, the Air Force is installing
a number of Radar Approach Control (RAPCON) Centers. These Centers,
which maintain high safety standards of aircraft control, require highly
specialized communications service, both internally and with other control
points. A modified version of the Bell System’s 102A key equipment is
being installed to provide safer, more efficient air-traffic service of this type.

Since World War II the United States Air Force
has greatly extended the use of radar for con-
trolling military air traffic. Personnel operating a
radar-control system are given a graphic display of
the location, direction of travel and speed of all air-
craft within the range of the radar set. To use the
advantages of radar methods, Radar Approach Con-
trol (RAPCON) Centers have been installed at
many Air Force Bases. These centers use radar
for departure and landing control of all traffic
within the traffic pattern of the air base, and ex-
tend this control from the visual limit of an airport
control tower to about 50 miles from the base.

The chief purpose of air-traffic control is to pro-
vide safe separation of aircraft in the control area,
especially those under instrument flight rules. Mod-
ern aircraft compound the safety problem by virtue
of the complexity of operation. The time element
has become increasingly important because many
jet planes now fly over 600 miles per hour. At this
speed, the aircraft is traveling one mile every six

seconds, or ten miles per minute. Another important
consideration is that the fuel consumption of jet
aircraft is very high, particularly below 20,000 feet.
Positive and definite landing preparations are
therefore necessary, since even a lapse of a few
seconds in traffic-control procedures could mean
the difference between safety and disaster.

The success with which RAPCON Centers con-
trol these high speed aircraft depends to a large
degree on a rapid and efficient voice-communica-
tion system. RAPCON Centers are furnished with
the No. 102A key equipment system. With this sys-
tem, several attendants, or controllers, can establish ©
direct communication with any one of many internal
and external lines. This key equipment was orig-
inally designed for the Civil Aeronautics Adminis-
tration to control civilian air traffic without the use
of radar. Certain features have been added for the
switching and other arrangements necessary to
meet the operational procedures required by the
RAPCON Center method of air-traffic control.

No. 102A key equipment was originally arranged
for one attendant at an operating position who had
access to telephone lines only. Two controllers —
a duty controller and an assistant — are normally
required at each RAPCON Center position, and
they have a relatively large number of direct air-
ground radio contacts. Thus the two attendants
must be able to share the telephone facilities and
to integrate closely the telephone and radio equip-
ment. They can independently use either the same
or separate telephone and key circuits, and either
the same or separate radio equipment at the con-
sole. Each attendant has a transfer key so that the
same telephone headset may be used on either tele-
phone lines or Air Force-owned radio equipment;
rapid transfer is possible from one to the other. The
convenience and savings in time gained by this ar-
rangement are of great value in the over-all opera-
tions. The transfer keys, line key units, and at-
tendant’s telephone-set jacks are mounted in the
Air Force-owned consoles as shown in the illus-
tration on page 490.

Rapid and positive intercommunication between
the operating personnel in a RAPCON Center is
imperative. For example, when the controller in
charge of departures (departure controller) finds
that an aircraft has been inadvertently taxied onto
an active runway, he must immediately contact the
controller in charge of incoming traffic (final con-
troller) to warn him of the existing hazardous con-
dition. The final controller can then direct any air-
craft on final approach to a temporary holding point
to avoid a collision. An “override” feature permits
this fast and positive intercommunication between
operating personnel. It is arranged so that any at-
tendant may have immediate communication with
an attendant at any other position in the RAPCON
Center, even though the called attendant may be
talking on a radio channel or a telephone line.

Figure 2 is a schematic diagram of the inter-
communicating circuits between two positions.
Either the duty or assistant controller, who share
the equipment at position No. 1, can override the
assistant controller at position No. 2 by operating
the associated line key. This key connects the con-
troller’s telephone circuit at position No. 1 — through
an induction coil and an operated relay — directly
to the telephone circuit of the assistant controller
at position No. 2. Operation of the key also lights
the line lamp at the overridden position to inform
the controller that he has been overridden by posi-
tion No. 1.

When the assistant controller’s transfer key at
position 2 is in the telephone position, a two-way

talking circuit is immediately established between
the controllers, whether or not the controller at
position 2 is connected to a telephone line. When
the key is operated for radio transmission, a relay
opens the transmitting circuit from the controller
at position 2 so that a one-way talking circuit is
established from the controller at position 1 to the
headset receiver of the controller at position 2.
This circuit is not connected to the input of the
radio transmitter because the message may be
misunderstood by the pilot and confuse him.
If the controller at position 2 wishes to talk to
position 1 over this circuit, he operates the key to
the telephone-lines position. The calling controller
may interrupt any conversation in progress. (Both
sides of the called controller's conversation, either
radio or wire, are heard by the overriding controller
through the sidetone circuit.) Similarly, either the
duty or assistant controller at position 2 can over-
ride the assistant controller at position 1.

The override feature is normally arranged so
that override calls can be made to only one (as-
sistant controller) of the two attendants at a posi-
tion. During light-load periods, however, the posi-
tion may be operated by only one attendant (duty
controller). For this case, the assistant controller
has a third position of his transfer key, as shown
in Figure 2. This position is called “single operator.”
When the duty controller is alone at the position,
the assistant controller's transfer key is operated

Fig. 1— G. A. Giddings examines arrangement of
modified 102A key unit for RAPCON operation.

to this single-operator position. This connects the
assistant controller's receiver circuit to the duty
controller's receiver circuit and extends the over-
tide features to the duty controller.

It is very important to record the conversations
of the attendants, especially when they talk to
pilots. A recorder jack panel is provided so that
any one of the Air Force-owned continyously-run-
ning tape recorders may be connected to record

all the radio and telephone conversations concern-
ing aircraft control.

All radio transmitters use a push-to-talk arrange-
ment and, to permit hands-free operation, this is
usually done with a footswitch at the position. How-
ever, this footswitch may be bypassed by operating
a footswitch-shorting key in the front of the console.
When this is done, the radio transmitter is actually
keyed with the locking or nonlocking push-to-talk

POSITION NO. 1 POSITION NO. 2
ASSISTANT
CONTROLLER
!
-- — TRANSFER KEY
SINGLE
‘RADIO TELEPHONE OPERATOR!
—>
INDUCTION | OVERRIDE
COIL OUCTION = RADIO ; H
DUTY OR TA RELAY RELAY
ASSISTANT =
CONTROLLER
| RI
= LINE '
INDUCTION
TO af DUTY
| TELEPHONE <=
CONTROLLE
| --
TRANSFER KEY
RADIO TELEPHONE
i <
!
!
!

Fig. 2—The override feature provides rapid communication between controllers in emergencies.

LINE 3
! )
—> TO OTHER LOUDSPEAKER
SL RELAYS THROUGH
_LINE 1 INTERMEDIATE
T SL RELAYS
/
LINE 2 / 5
LOUD- | <— y
SPEAKER T
TO OTHER
SL RELAYS
Se | OTHER POS
ASSOC WITH
| SAME TRANS
A INE
|
LINE LAMP LINE LAMP
SWITCHHOOK |

Fig. 3 — During eS of heavy traffic or in an emergency, the “hot line” arrangement makes possible
direct communication between the RAPCON Center and the airport control tower.

switch in the cord of the telephone headset. The
53-type headsets used have a 12-foot retractile
cord, which permits the attendant to move from
his position and still talk on radio channels.
One-way “hot” lines (lines continuously open for
transmission ) are installed in the system to provide
fast, direct and positive communication between a
RAPCON Center and the associated airport control
tower. This arrangement is needed in periods of
very heavy traffic, and especially so in case of an
emergency. Normally one hot line runs from
RAPCON to the tower and either two or three from
the tower to RAPCON. Figure 3 shows the special
termination arrangement for these hot lines. The
tower controller can talk immediately to a position
in the center by lifting his telephone handset and
operating a line-selection key to the line associated
with the called position. The switchhook contacts in
the handset transfer the “receive” line from the
loudspeaker to the handset receiver and connect the
talking battery to the handset transmitter. The con-
troller at position 1 in the RAPCON center can
talk immediately to the tower by operating a line
key which activates a relay associated with that
position. The relay performs four functions. (1) It
lights the line lamps associated with the transmit
line at that and all other positions to indicate that
the line is in use. (2) It transfers the receive line
at that position from the loudspeaker to both the
head telephone set of the controller's receiver and
a bus circuit in the receive line to other relays asso-
ciated with the same receive line. (3) It connects
the controller's head telephone set transmitter to
the transmit line. And (4) it connects two resistors
between the transmit line and the controller's re-

ceiver circuit to provide sidetone to the controller.
In a similar manner, the controllers at other posi-
tions can talk to the control tower by operating the
line key associated with the transmit line.

Both controllers at a position in the RAPCON
Center have individual loudspeakers in the console
for monitoring radio channels when their headsets
are connected to the telephone lines. When a con-
troller’s headset is connected to radio channels, he
may operate a switch in the console to cut off the
loudspeaker and to permit him to listen with his
headset receiver only. However, the key equip-
ment is arranged so that if the loudspeaker-cutoft
switch is left on when the attendant returns to tele-
phone-line operation, the loud-speaker is automati-
cally connected to the output of the radio receiver.
This ensures that the radio channels will always be
monitored.

The Air Force plans to use RAPCON Centers at
overseas locations as well as in the Continental
United States. At all U. S. installations, Operating
Telephone Companies install and maintain the RAP-
CON telephone equipment. Key equipment for the
overseas Centers, however, is pre-assembled and
packaged in kit form by the Western Electric Com-
pany and is sold directly to the Air Force. It is in-
stalled and maintained, therefore, by the Air Force.

These additions to No. 102A key equipment, for
use at both United States and overseas RAPCON
installations, speed the control and promote the
safety of handling the high-speed military aircraft
of today. They comprise another step in a series of
measures being taken to keep communications in
pace with the continually growing traffic control
problem of the Air Force.

G. A. Gipp1ncs, a native of Pontiac, Mich., received a B.S. degree in Electrical
Engineering from Michigan State University in 1941. He immediately joined
the Michigan Bell Telephone Company, and worked in their Plant Department
for twelve years, except for three years during World War II when he was on loan
to the Laboratories for work on war contracts. In 1953, he transferred to the
Laboratories and was concerned with the development of station systems for
military applications. Mr. Giddings recently transferred to the O. & E. Depart-

For the large information-carrying capac-
ities required of future communications
systems, it is necessary to go to shorter
wavelengths and greater bandwidths. The-
ory and experiment have shown, however,
that millimeter waves are sometimes se-
verely attenuated by rain and by certain

‘ | gases in the air. To get precise information
on this point, a very accurate method has
; Vi. ¥ been devised for measuring such losses

Most long-distance telephone and television traf-
fic in the Bell System is handled by coaxial cable
and microwave radio-relay systems. Coaxial cable,
because of its shielding and underground installa-
tion, is relatively immune to atmospheric disturb-
ances, but radio services must always be designed
with careful consideration of the effect of the at-
mosphere on the propagation of radio waves.

Microwave radio-relay systems — TD-2, TH (now
under development) and TJ — use the atmosphere
as a low-loss medium through which the radio energy
is propagated. This may give the impression that
the atmosphere is transparent to all radio frequen-

cies; actually, however, as the frequency increases,
" attenuation is severe in certain bands.

Transmission losses encountered by radio waves
in the atmosphere can be divided into two general
categories: those due to precipitation — rain, snow,

principally oxygen and water vapor. At 4,000 mega-
cycles, the frequency of the TD-2 radio-relay system,
such losses are so small that they can be neglected
for most practical purposes. But when the operating
frequency is increased to about 10,000 mc, the
frequency of the TJ system,* attenuation by rain

becomes an important consideration. This type of
loss increases rapidly as one proceeds to still higher
frequencies, and at 60,000 mc it has a value of 20
decibels per mile for a moderately heavy rain. For-
tunately, fog causes much less attenuation, princi-
pally because there is a lesser amount of precipitate
per unit volume of air. Likewise, because of its
crystalline structure, snow attenuates radio waves
much less than rain.

At the higher frequencies, the second category
of atmospheric loss is also important. Even if it is
not raining or snowing, the oxygen and water vapor
that constitute part of our atmosphere attenuate
radio waves appreciably in the region of millimeter
waves (frequencies between 30,000 and 300,000
mc). The oxygen molecules in the air become res-
onant to the frequencies of mm waves and absorb
much of the propagated energy. As shown in Figure
1, absorption occurs chiefly in the band from 50,000
to 70,000 mc, with an attenuation of more than 20
db per mile at 60,000 mc. At this frequency, there-
fore, oxygen attenuation of mm waves is about the
same as that from a moderately heavy rain. Also,
during rain, the two attenuations are additive, so
that transmission in the region of 60,000 mc would
be very difficult.

that frequencies higher than those employed in
present microwave systems are impracticable, but
losses may limit the use of mm waves in the at-
mosphere to very short ranges, Also, transmission
losses can be avoided through the use of waveguide
systems, and the Laboratories is now concentrating
on this type of system in which the “atmosphere”
or propagation medium within the waveguide can
be controlled.*

Any research into possible mm-wave systems,
however, depends upon an accurate knowledge of
the transmission losses. Described here is a precise
method devised for making an accurate determina-
tion of atmospheric loss. It has proved to be reliable
for studies of attenuation over a broad range of
frequencies in the mm-wave region. The method
is demonstrated by experiments that determine ab-
sorption by the oxygen in the air. In these experi-
ments, mm waves are propagated through the at-
mosphere toward two reflectors located at different
distances from the transmitter, so that the difference
in the energies of the two reflected waves is a
measure of the absorption.

In principle, attenuation by the atmosphere can
be determined simply by radiating a mm wave
from a transmitting antenna to a receiving antenna.
If the gains of the antennas are known accurately,
and if the antenna beams are narrow enough to pre-
clude reflections from the ground and from objects
along the path of propagation, one can calculate
the power that would be received provided the at-
mosphere had no loss (often called the free-space
power ). Thus, the calculated power minus the ob-

24
j
a
o YY Y Y
Y
WH
= 12%
Y ABSORPTION BY-~
Eo OXYGEN IN THE AIR
(SEA-LEVEL
z PRESSURE)
uw 7 P J
|

sorption and calculated curve, showing close agree-
ment between theory and test results.

Fig. 2—R. A. Desmond inspecting polyethylene
lens on conical horn antenna. Antenna served for
both transmitting and receiving the test signals.

served power provides a measure of the atmospheric
attenuation between the transmitter and receiver.

Unfortunately, the accuracy of this one-way trans-
mission method is seriously affected by slight in-
stabilities at the transmitting and receiving termin-
als. Moreover, if one wishes to measure a number
of frequencies, the method is time-consuming, since
oscillators at both the transmitter and receiver must
be adjusted for each measurement.

A more accurate and more convenient experi-
mental procedure is indicated in Figure 3. This is
the two-way transmission method presently used
at the Holmdel Laboratory. The mm waves at vari-
ous frequencies are generated by a mm-wave oscil-
lator and are directed by an antenna toward two
corner reflectors R; and Ro. These reflectors are of
the tri-hedral type investigated at the Laboratories.
They have the configuration of an inside corner of
a cube, and they direct the incident beam back
upon itself. Reflectors of this type were used be-
cause they are less sensitive than flat reflectors to
minor misalignments in position.

The transmitting antenna also receives the re-
flected signals. First, the two reflectors are placed
side by side facing the antenna, and their relative
reflecting properties are determined by comparing
the reflected power when the reflectors are covered
alternately with a highly absorbent, non-reflecting
material. This calibration is carried out at all fre-
quencies of interest.

The reflectors are then separated as shown in
Figure 3. Knowing the relative reflecting properties

and the distances d, and d. from the antenna to
the two reflectors, one can readily calculate the
ratio of the powers that would be reflected from
R; and Re if there were no loss in the atmosphere.
The difference between the measured and calculated
ratios then represents the attenuation of that portion
of the atmosphere between Rr; and Rp. Since the
measurement is in terms of ratios rather than ab-
solute values, it is independent of the gain of the
antenna and of the absolute operating levels of the
measuring set.

The method of measuring the reflected signals
is illustrated in Figure 4. The transmitted mm-wave
signal is frequency modulated in a “sawtooth” man-
ner, and the modulating frequencies have a small
total excursion, Fr. The transmitted signal — solid-
line sawtooth curve in Figure 4(a) —is radiated
from the antenna to the near corner reflector, Rj.
Upon being received, the reflected signal is delayed
with respect to the transmitted signal by a time, ty,
equal to twice the distance to the reflector divided
by the velocity of light. This delayed signal is indi-

Fig. 3—The two-way transmission method: re-
flectors are first placed side-by-side and then spaced
at distances d,; and d, from the antenna.

Fig. 4— Transmitted and reflected signals fer (a)
near reflector R, and (b) far reflector Re.

Fig. 5 — D. C, Hogg, left, and A. B. Crawford ad-
justing waveguide assembly used in experiments.

cated by the dashed-line sawtooth curve. Ducing
a portion of each cycle, 1,-t;, the transmitted and
received signals differ in frequency by a constant
value, f. Power at this difference or “beat” fre-
quency is amplified in a narrow-band amplifier
centered on f. Because during time t, there is a
much larger value of beat frequency, the amplifier
will have no output for this period. The result,
therefore, is a series of pulses at frequency f, each
of length 1,-t,, and with a repetition rate 1/1.

For the far corner reflector, Ro, the period of the
sawtooth modulation is increased in proportion to
the increase in distance, as indicated in Figure 4(b).
Consequently, the difference frequency, f, is identi-
cal to that obtained with the near reflector. Also,
the frequency excursion, F, is held constant, which
means that the average power output of the trans-
mitter remains unchanged. Thus, the same amplifier
can be used for both the near and far reflectors,
and a single meter can be used to compare the
difference between the received powers. Actually,
the signals are adjusted to give identical meter
readings for the two cases, and the power difference
is read from a precision attenuator.

A block diagram of the electronic apparatus is
shown in Figure 6. In brief, the sawtooth generator
in the upper left of this illustration modulates the
mm-wave oscillator at the lower left, and power is
fed to the antenna at the lower right. Part of this
power, however, is delivered through a 6-db coupler
to a balanced converter. The reflected signal is
received by the antenna and is also delivered to
the converter, via the 3-db coupler. This balanced
converter, which uses two wafer-type millimeter
rectifier units, mixes the transmitted and delayed
signals to produce the difference or intermediate

The nF source used for most of these measure-
ments was a low-voltage reflex klystron developed
by E. D. Reed of the Laboratories.* It has an av-
erage power output of about 12 milliwatts over
the 50,000 to 60,000 mc range. The mr amplifier is
centered on a frequency, f, of 750 ke and has a
bandwidth of 300 ke. This bandwidth is narrow
enough to give a good signal-to-noise advantage
and is wide enough to take care of any non-linearity
in the sawtooth modulation. Backward-wave oscilla-
torst are also used as sources of mm-wave power
for this type of measurement.

The measurements shown by the points in Fig-
ure 1 were made with this equipment. They were
taken during winter days when the air was dry
enough to eliminate effects due to water vapor. The
solid curve in the illustration represents a theoreti-
cal calculation based on absorption by oxygen. Be-

cause of the good agreement between the measured
and calculated values, attenuation by dry air in
the measured band of frequencies is believed to
be due mainly to absorption caused by resonance
of the oxygen molecules. In this band, water vapor
attenuates radio waves much less than oxygen. Even
in conditions of relatively high humidity, water
vapor increases the attenuation only about one-

Fig. 6— Transmitted and reflected signals are
mixed in a balanced converter, amplified, and de-
livered to an oscilloscope and meter or recorder.

in Electrical Engineering at Ohio State University in 1928 and joined the Radio
Research Department of the Bell Telephone Laboratories the same year. For a
number of years he was concerned with ultra-short wave measuring techniques
and propagation studies. During the war years he worked on various microwave
components for radar systems. In recent years he has headed a subdepartment
in Radio Research at the Holmdel Laboratories working on microwave antennas,
line-of-sight and beyond-the-horizon radio propagation and point-contact recti-
fiers. He is a Fellow of the Institute of Radio Engineers and a member of Sigma Xi.

D. C. Hoce, a native of Saskatchewan, Canada, spent five years with the Cana-
dian Army during World War II in radar and telecommunications work in Britain
and Europe. After the war, he received the B.Sc. degree from the University of
Western Ontario, London, Canada, in 1949, and the M.Sc. and Ph.D. from
McGill University, Montreal, in 1953. At McGill University, his research was
centered upon microwave diffraction. Mr. Hogg joined Bell Laboratories in 1953.
He has been concerned with research on over-the-horizon microwave radio
propagation and with atmospheric attenuation of millimeter waves.

An automatic instrument has been developed at
Bell Laboratories for rapidly measuring and record-
ing very small imperfections in pitch unifonnity of
repetitive structures. The instrument, termed a
“microdeviometer,” is presently being used for eval-
uating the helices of traveling-wave tubes, but it can
be used equally well for measuring the pitch uni-
formity of other periodic structures such as preci-
sion screws and the grids of electron tubes.

In a traveling-wave tube, the wave to be ampli-
fied is launched on one end of a helix, which is
wound in such a manner that the wave is effectively

slowed down along the axial direction of the helix. :
When the axial velocity of the wave equals the —

velocity of an electron beam focused through the
center of the helix, amplification results. Thus, the
helix must be very precisely dimensioned if the tube
is to meet design requirements.

In the microdeviometer, the output is a pen re-
cording which tells at a glance the deviation of each
successive relevant part of the periodic structure

H. T. Closson examines record of precision measurements
of pitch uniformity obtained with the new microdeviometer.

from the ideal, the ideal structure being one in
which the length of each repeated section is exactly
the same as every other. Longitudinal displace-
ments are indicated to an accuracy of one micron
(1/1000 mm). A traveling-wave tube helix can be
completely evaluated in less than 5 minutes, com-
pared to more than two man-days necessary by
previously available techniques.

The apparatus incorporates a combination of opti-
cal, electronic and mechanical technology. Essential
features include: (1) an optical grating which pro-
vides a very accurate distance scale, (2) an optical
system for ascertaining the position of the part to
be measured with respect to the chosen scale, and
(3) an electronic method of analyzing this informa-
tion and recording it on a strip chart.

The part to be measured is rigidly mounted on a
moving platform on which is also mounted the pre-
cision optical grating. This grating moves past a
similar fixed grating, so that a beam of light is in- -
terrupted when the rulings on the two gratings are
superimposed. The light beam falls on a photocell,
where the interruptions produce electrical pulses
representing accurate distance increments of one
micron. Another combination of a fixed beam of
light and a photocell produces an output pulse
when an element of the periodic structure passes
a fixed reference point. In other words, pulses from
the helix are obtained for comparison with the very
accurate pulses from the precision gratings.

The pulses are fed to an electronic computer
which evaluates the deviation from the ideal. This
information is then recorded on a chart in such a
manner as to provide a direct reading of the actual
deviation of each element.

In the accompanying photograph, the mechani-
cal-optical section of the microdeviometer is in the
center, and the specially designed electronic com-
puter is at the left. The pen-recording strip chart
is obtained from the unit seen at the lower right.
The inset view shows a typical record, where the
positions of the horizontal bars represent helix-turn
deviations from the ideal.

Since outside plant makes up about 37 per cent of the total Bell System
plant investment, Laboratories’ development effort directed toward the
improvement of outside plant facilities and techniques pays large
dividends. The “punched-sleeve” method of cable splicing is a good
example of this type of development. The new method results in the
splicer’s making better joints more rapidly and efficiently than by the

Each year the Operating Companies of the Bell
System add about 50,000 sheath miles of telephone
cable to their outside plant. These cables vary
in size from the smallest aerial distribution types
containing 6 pairs of wire to the big feeder cables
containing as many as 2,100 pairs, running in
underground conduit systems. The cables are in-
stalled in lengths that range from less than 200
feet at one extreme to 2,000 feet and more at the
other. A work force of more than 14,000 cable
splicers must make more than 300 million conduc-
tor joints each year in splicing together several hun-
dred thousand sections of cable.

Although many construction and maintenance
operations of the outside plant forces have been
modernized, and although some have been highly
mechanized, the techniques for joining cable con-
ductors have remained virtually unchanged since
the beginning of the telephone business. The time-
honored method of joining two or more paper or
pulp-insulated cable conductors is simple and re-
quires a minimum of equipment. The cable splicer,
or his helper, slips a cotton sleeve over one of the
conductors before the joint is made. He then brings
the conductors together, cuts them to proper length,
removes a few inches of insulation, twists the bare
conductors together, cuts them to final length,

and slips the cotton sleeve over the joint for insula-
tion to replace that previously removed.

The mechanical and electrical stability of joints
produced by this method is generally satisfactory
for today’s exchange distribution plant which is
subjected to ac ringing voltages and sizeable trans-
mitter currents. Because high-resistance joints do
occasionally develop, however, the twisted conduc-

Fig. 1— Pneumatic presser and sleeve used in
punched-sleeve cable splicing. The sleeve assembly
consists of a tube made of the same metal as the
conductors to be joined (aluminum or copper) with

The Bell System is constantly seeking ways to
cut construction costs, and methods which consist
principally of hand operations are special targets
for improvement. This, together with the need for
higher quality joints to meet the requirements of
modern and future circuits, which operate at low
de voltages and small currents, has stimulated a
search for new methods of joining conductors.

In the search for better splicing methods, one
must remember that the splicer seldom does his
work under ideal conditions. He must work in
hot or cold, dry or wet weather, or in clean or dirty
surroundings, and so must his equipment. He must
carry all the equipment to the job and it must be
rugged enough to stand frequent handling. If he
needs electric power, it must usually come from a
portable generator. Thus many joining methods
which would be satisfactory in the laboratory would
not be practical under field conditions.

The groundwork for the new approach to the
conductor-joining problem was laid by analyses of
time and motion studies of the old method and of
labor and material costs. Guiding objectives were
developed as follows:

4. It should be possible to join the various com-
binations of conductor gauges with a minimum
number of sizes of parts.

. Power should be used to reduce worker fatigue.
. The method must be adaptable to the varied
conditions of field splicing.

Fig. 2 — Cross-section of aluminum punched-sleeve
splice showing how insulation on conductors is dis-
placed and metal-to-metal contact is made between
conductors and metal sleeve.

Fig. 3—L. W. Faulkner checking resistance of
joints made by punched-sleeve method.

Long and favorable experience in the Bell System
with compreggion types of joints on bare conductors
suggested a Bethoa in which a simple metal sleeve
could be slipped over the ends of the conductors
and then deformed in such a way as to penetrate
the insulation and produce a joint. Early experi-
ments with such sleeves and with toothed dies for
deforming them, showed that the general approach
was promising.

Study of the proposed method showed that sev-
eral requirements would have to be met. The tangs
produced by the die teeth must penetrate the insu-
lation to reach every conductor, but must not sever
any conductors. The contact areas between the
tangs and the conductors must be adequate in size
to furnish low resistance paths, and must be held
together by stresses sufficient to prevent corrosion.
The stressed parts involved in the contacts must
have elastic reserve to provide permanent joints.
The insulation must not be held under compression
in such a way that changes in temperature and
humidity could result in release of the stresses in
the deformed parts.

To obtain optimum performance, a program of
intensive comparison testing was begun for many
different designs of toothed dies and variations of
sleeves. Many types of tests for determining the
quality of the joints produced, particularly from the
standpoint of permanence, were studied. The most
useful test has been one in which the joints are
subjected to cycles of temperature change. Changes
of temperature can be expected to cause displace-
ments in the joints, unless the stresses involved are
sufficient to prevent them. If the joint can withstand
repeated wide temperature fluctuations, the stresses

In this test, the joints are cycled between an oven
maintained at 150°F and a bath of liquid nitrogen
at —324°F. The higher temperature is normally
reached by joints in an aerial cable splice under
exposure to the sun. The lower temperature, while
it bears no relation to any service condition,: was
chosen partly as a matter of testing convenience,
but also because it provides a wide temperature
range with considerable thermal shock when the
warm joints are plunged into the liquid. The test
is carried out automatically by a special machine,
and joints are normally subjected to 100 of the
temperature cycles. Measurements of joint resist-
ance are made before and after the cycling. Cor-
relation has been obtained between the results of
these tests and actual aging under field conditions.

The method finally developed involves slipping
a sleeve over the ends of the two or three conduc-
tors to be joined, and “punching” the Peeve between
toothed dies in the jaws of a pneumatic tool, pow-
ered from the same tank of compressed nitrogen
that the splicer uses to pressure test cables and
splices. The sleeve consists of a tube made of the
same metal as the conductors to be joined (alumi-
num or copper), with a jacket of plastic that is
closed at one end. The punching operation deforms
the sleeve wall and the conductors in such a way
that a combination of shearing and compressive
forces displaces the insulation, making metal-to-
metal contacts. This operation produces punctures
in the plastic covering of the sleeve. These punc-
tures are not detrimental, however, since they do
not lower the dielectric strength between the paper-
insulated conductors. Because the jacket material
springs out at the punctures, there is no possibility
that the metal sleeves on two joints will touch.

For optimum performance it has been found nec-
essary to use different types of dies for punching

aluminum and copper sleeves. This is due to the
different mechanical properties of the two metals
relative to those of the insulation. Only two sizes
of aluminum sleeves and three sizes of copper
sleeves are required to handle the range of con-
ductor combinations encountered in the field, from
19 gauge (0.036”) to 26 gauge (0.016”).

The introduction of a power tool into the cable
splicing art is an important step in mechanizing
this basic technique of cable plant construction.
The punched-sleeve method produces conductor
joints of improved electrical quality in comparison
with the twisted joints. The evidence of extensive
field trials also gives promise of substantial reduc-

Fig. 4— Pneumatic presser being used to make
punched-sleeve joint in paper-insulated conductors.

tions in cable-splicing costs. For the future, the
advent of cable with plastic-insulated conductors
introduces new and more exacting requirements
and makes further work necessary on the challeng-
ing problem of conductor joining.

W. C. Kietrevper had been engaged in outside plant tool and wire develop-
ment at the Laboratories for five years when he received the B.S. degree in M.E.
from Cooper Union in 1934. In 1939, still a member of Outside Plant, he trans-
ferred from projects in wire and wire attachments to cable joining and mainten-
ance, in which he has worked on problems such as the splicing of coaxial cables,
splicing methods for cables having new sheath structures, and improved methods
for joining cable conductors. This work was interrupted during World War II
when he spent three years in the development of military equipment. He has
recently been in charge of the group working on cable joining methods.

The telephone industry must show the commis-
sions and the public that the only way to telephone
progress is through telephone prosperity, A. T. & T.
President Frederick R. Kappel said in a talk before
the United States Independent Telephone Associ-
ation in Chicago on October 14.

“Telephone service has been a low-earning enter-
prise now for a long time. It ought not to be,” Mr.
Kappel told the annual convention. He said a large
segment of the public and “too many” commissions
seem to think that low earnings mean low rates and
good earnings mean high rates; whereas the fact is
that good earnings, in the long run, mean quality
service at lower cost to the user.

“Is it asking too much of regulatory commissions,”
he continued, “to exercise in fullest measure their
practical judgment, their imagination and their
political courage?

“I am sure it is not. And I am especially sure of
this when I reflect that the problems which confront
the regulator when a business is successful... are
as nothing compared with the problems which con-
front him when a business doesn’t have the money
to do what ought to be done.”

Mr. Kappel said he “cannot believe” that many
states expect to attract other industry and raise
employment and prosperity “as they regulate tele-
phone expansion and employment down.

“It is our job to demonstrate that every state
needs our financial good health, not only for what
this means in direct telephone employment and
wages, but equally or even more for what we can
do to help make the state attractive to others.

Turning to the field of labor relations, Mr. Kappel
said that what telephone employees really know
and believe about their company depends on how
diligent the company is in giving employees the
facts and demonstrating its sincerity.

“I saw a union editorial the other day that had the
Bell System waxing rich and practically choking on
fat profits,” he said. “This kind of thing is so absurd
you may wonder why I even mention it. The reason
is that the problems which unions and manage-
ments are concerned with are so important that
there just isn’t room for careless or misleading talk.

“You and I know that the telephone companies
are bound to provide wages and working conditions
that compare favorably with other industry and

offer attractive opportunity for willing and indus-
trious men and women.

“Frivolous and unconsidered statements can only
cause harm—the more so if by silence we seem to
give them our consent. What we need is to get such
a steady stream of truth flowing that there’s no
room in the river for anything else.”

Mr. Kappel referred also to competition in provid-
ing communication services. “It seems there are
quite a few non-communication companies today
that would like to provide a considerable part of
their communications themselves, without depend-
ing on the common carriers,” he said.

“Of course, this goes against the basic principles
and experience which have shown that the public
interest depends on common carrier service. Indis-
criminate licensing of non-common carriers to build
their own systems would not only sacrifice the most
efficient use of the radio spectrum; it could very
seriously interfere with the ability of the telephone
companies to serve the public at reasonable prices.

“We are sure,” he continued, “that common car-
rier-service results in lower costs to the public. We
are confident it also makes possible much more effi-
cient use of the radio spectrum. We know a strong
common-carrier network is a much greater asset in
time of emergency or war than a fragmentized
hodge-podge of private systems could ever be.”

Building future telephone management, Mr. Kap-
pel said, “is the responsibility of every boss in the
business. ... The great essential is to have the kind
of working atmosphere that gives people air and
room and freedom and incentive to grow. We'll do
the best job, I’m sure, when—and only when—every
boss acts on the understanding that an indispensable
part of his assignment is to . . . encourage the
growth of his subordinates.”

Mr. Kappel congratulated the USITA on its 60
years of progress and its vital part in the total
accomplishment of the industry. “The way things
are nowadays, none of us have much time to be
looking back. The future isn’t waiting for us. It’s
rushing right at us,” he said.

“We in the telephone business must meet these
changes together, for ours is one single industry and
our service is indivisible. Far more than in other
types of business, the progress we make depends on
how effectively we combine our efforts.”

With the expansion of direct distance dialing
and automatic alternate routing, transmission
maintenance requirements for long-distance
trunks are more exacting. To assist the main-
tenance forces in gathering transmission data
more efficiently, new circuits, including a com-
puter unit, have been incorporated into the
intertoll trunk-test equipment. This equipment
speeds the analysis of transmission perform-
ance and thus expedites maintenance of trunks.

Long-distance telephone channels, called intertoll
trunks, must be maintained at high transmission
efficiency if service is not to be interrupted or im-
paired. This is and always has been a general re-
quirement for long-distance facilities, but it is even
more important now that completely automatic and
highly versatile switching systems are enabling
more and more people to dial their own long-
distance calls without operator assistance.

A long-distance communication path may require
several separate transmission links connected in
tandem (seven links is the usual maximum), and
with fuily automatic alternate routing, the path
itself will be only one out of several possible alterna-
tives. When operators were involved in all long-
distance calls, they could frequently detect any
degradation of transmission quality and report it as
an aid to the maintenance forces. Now that tele-
phoning is becoming more completely automatic,
however, the discovery and measurement of trans-

mission deviations must also become more auto-
matic. To insure that necessary adjustments are
promptly made, the maintenance force must more
closely observe intertoll trunk performance. This is
true both of the operational aspects of trunks — the
many switching and regulating actions that take
place in setting up the trunk connection — and of
transmission performance — whether voice and sig-
nals are transmitted over the trunk without exces-
sive deviation from design values.

To aid maintenance, several types of testing and
measuring circuits have been developed. As shown
in simplified form in Figure 2(a), tests can be per-
formed from a toll test board at an originating
(“near-end”) office, by making connection to an
automatic transmission-measuring and noise-check-
ing circuit at the terminating or “far-end” office.
However, because personnel at the near-end office
set up the tests and record the data, this arrange-
ment is not fully automatic. Consequently, addi-

<— MINUS PLUS
MAGNITUDE OF DEPARTURE FROM DESIGN VALUE
Fig. 1— Normal distribution curve for random
variation of transmission values about design value.

The automatic transmission test and control cir-
cuit and the recording teletypewriter printer circuit
in Figure 2(b) have also been added to the near-
end test equipment. These circuits, in conjunction
with the AOIT, perform fully automatic two-way
transmission-loss measurements and noise checks,
and also provide a printed record of the operational
or transmission-test results.

With this test gear, however, a large amount of
data-plotting is still required, and more recently a
computer-type circuit has been added to the test
facilities to simplify the presentation of data in
usable form. But before describing this circuit, it is
well to review the sort of data-gathering operation
required in the transmission-testing of trunks.

Transmission performance of intertoll trunks is
measured in terms of how much a given trunk
deviates from a specified or design loss. For ex-
ample, over a certain trunk the transmitted energy
may decrease in power by 6 db when it is desired
that the actual loss should be only 5 db. Transmis-
sion performance is then described by saying that
this trunk has a transmission deviation of +1 db.
However, trunk use becomes, to a considerable
extent, a matter of chance selection, and for this
reason, performance is considered by statistical anal-
ysis of a large number of trunks or by groups of
trunks, rather than on an individual trunk basis.

Experience has shown that when a sufficiently
large number of transmission measurements are
made, the variations, taken as a whole, will follow a
normal distribution curve as shown in Figure 1.
Most of the trunks in a group will be fairly close to

* TERMINATING OFFICE MAY BE NO. 4 OR NO. 5 CROSSBAR;
CROSSBAR TANDEM, OR STEP-BY-STEP INTERTOLL

Fig. 2 -— Semi-automatic and full-automatic circuits for
performing transmission and operational tests of long-dis-

their specified loss values, while some trunks may
deviate 2 or 3 db or more. In the illustration, this
fact is reflected by the peak seen in the curve
at zero deviation with gradually decreasing num-
bers of measurements on either side. However, be-
cause the specified losses are not necessarily the
same for each trunk in a large group, the distribu-
tion of deviations usually will not be symmetrical
about zero, but will center on an algebraic average
of all deviations. The displacement from the normal
is known as “bias” and indicates the general trend
of deviations in the group.

Statistical analysis of all deviations, both above
and below the specified values, provides the
“standard deviation” (o). As indicated in Figure 1,
the standard deviation is the cross-hatched area
under the curve. With normal deviation, about 65
to 70 per cent of all deviations will occur in this
region, and in transmission parlance it is called the
“distribution grade.” If the distribution grade is low,
the group of trunks is good, with most trunks near
their assigned values. If it is high, some of the
trunks need readjustment.

Although the trunks are thus considered as a
group, the data for the curves must be obtained
from separate measurements on each trunk. When
transmission grade is calculated manually, the pro-
cedure of recording a large number of measure-
ments is somewhat simplified by using a special
data sheet. Part of one of these sheets can be seen
in Figure 4, The procedure consists first of subtract-
ing the specified loss from the actual measured loss
of the trunk. For each of the resulting deviation
values, a “stroke” or mark is then placed on the data
sheet. For example, suppose the first deviation value
measured fell between —1.25 and —1.75 db. On the
horizontal line representing this band, a stroke
would be placed just to the left of the vertical line
for tally number one. All successive values in this
same —1.25 to —1.75 db range would later be
stroked in the later tally positions along the hori-
zontal line, and all other deviation values would be
stroked along the other horizontal lines in the same
manner. This is continued until all the deviations
have been calculated and recorded, so that the total
number of strokes as observed from the tally posi-
tion of the last stroke on each line is the total num-
ber of measurements within each of the one-half db
deviation bands. It will be seen that an envelope
enclosing these strokes is similar to the distribution
curves of Figure 1, except that here the graph is
oriented horizontally. The data sheets also give
visual clues to areas where maintenance effort

Fig. 3— Registers which score number of deviations
in various decibel-bands, seen above telety pewriter
which records results of tests.

There are a number of other operations per-
formed with the data sheet before the information
is brought to its final form, but from this description
it is obvious that when large numbers of deviations
are involved, manual subtraction and totalization of
the data can become prohibitively time-consuming.
The new computer included in the near-end testing
equipment greatly reduces the amount of manual
work required. This circuit automatically calculates
all the individual deviations and totalizes them in
one-half db ranges according to sign. That is, the
operations of subtracting the specified from the
actual values, and of adding by strokes, are per-
formed automatically. The maintenance people
merely read the total number of strokes for each
one-half db band from message registers. Only the
final stroke in each range is placed on the data
sheet, after which the sheet is handled in the cus-
tomary manner.

In addition, the associated recording teletype-
writer provides a record of each test. A portion of
such a record is shown in Figure 5; it gives main-
tenance personnel a number identifying the trunk
that was tested, the specified loss, and the deviation
from this specified loss in each direction of trans-
mission (in and out of the office). For example, the

specified loss for trunk number 1,378 is 7.5 db. The
test results indicate transmission deviations of —5.2
db in the far-to-near direction and +-0.7 db in the
near-to-far direction. For simplicity, the decimal
point between the tenths and units digits for speci-
fied loss and deviation entries is not recorded by the

Fig. 4— Portion of special data sheet used in
recording of transmission deviations.

printer. In addition, for an entry of less than 10 db.
the tens digit is omitted, again for simplicity.

The record also gives a symbol to indicate when
measurements exceed transmission or noise limits,
or when circuit failures occur to prevent satisfactory
completion of the test. For instance, on trunk num-
bered 1,377, the noisé exceeded limits in the far-to-
near direction, as indicated by the symbol n. On
trunk numbered 1,378 the deviation exceeded wide
deviation limits in the far-to-near direction, as indi-
cated by the vu in the appropriate column. The
record for trunk numbered 1,267 indicates, by the
symbol y, that far-end equipment failure prevented
completion of the test. In Figure 5, the character B
on the test record indicates that the trunk was busy
at the time a test was attempted, and a indicates
that the test call did not successfully complete to
the terminating office.

Basically, the computer duplicates the operations
described above for the manual determination of
transmission deviations and their proper sign (+ or
—). This information is passed to the teletypewriter
for recording. A “class” relay associated with each
trunk supplies the specified loss value, and this is
subtracted from the measured loss value. The meas-
ured loss values are stored in relay memory circuits
that have registered the test results. The values are
in decimal form — between zero and 19.9 db — and

before being fed into the computer, they are trans-
lated into their biquinary equivalents. The biquin-
ary system is a method of encoding any digit from 0
to 9 in such a way that it can be registered by oper-
ating two out of seven relays. Five of these relays
(the “quinary” part) represent either 0, 1, 2, 3, 4, or
5, 6, 7, 8, 9, depending on which of the remaining
two relays (the “bi” part) is operated. Since two and
only two relays must be operated for each digit, the
computer can be made self-checking to the extent
that if more or fewer than two relays operate, or if
two relays operate in an invalid combination, an
error is automatically detected. After a subtraction
is completed in the computer, the information is
passed to the teletypewriter in a form suitable for
its operation.

In the design of the computer, it was decided that
it would be convenient to have a circuit that would
only add and that would perform the required sub-
traction by the “nines complement” method. It may
be recalled from arithmetic studies that a “nines”
method is sometimes used to check a subtraction
by adding the complements. The computer uses a
version of this device to perform subtraction by
addition of the complements.

For example, a trunk might have a specified loss
of 7.2 db; this quantity would appear in the com-
puter as 99.9 minus 07.2 or 92.7. Suppose now that
the actual loss of this trunk is 9.1 db. The computer
adds 09.1 to the 92.7 to get a sum 101.8. Or, suppose
the actual loss of the trunk is 5.2 db, in which case
the arithmetic is 92.7 plus 05.2 equals 97.9 db. It
will be noticed that the sum is greater or less than
100.0, depending on whether the actual loss is

Fig. 5 — Teletypewriter record of computer-ana-
lyzed results of transmission tests. Data are used
for rapid maintenance of trunks.

greater or less than the specified loss. The mathe-
matical expression is (99.9 — S) -+ M = D, where S
is the specified loss, M is the actual measured loss,
and D is the “deviation.”

This “deviation,” however, does not represent the
true sum, which must be the actual deviation from
the specified loss. With a number over 100 like the
101.8, the first digit “1” is dropped and 0.1 is added,
to result in the true deviation of plus 01.9 db. With
a number below 100 like the 97.9, the nines com-
plement of the sum (99.9 minus 97.9) yields the
true result of minus 2.0 db. In this manner, the com-
puter is able to give an indication of the correct
sign of the result, and all values are recorded by the
teletypewriter with their appropriate + or — signs.
Several entries of this type can be seen in the tele-
typewriter record shown as Figure 5.

Thirty-three message registers at the near end
totalize the individual transmission deviations for
each 0.5 db increment from +8 db to —8 db accord-
ing to sign. This is done so that the values will agree
with the increments on the special data sheet used
for transmission analysis. An additional message
register totalizes the number of individual one-way
measurements, and its reading should be equal to
the total of the readings on the thirty-three devia-

tion registers. Each register, equipped with a man-
ual reset key, is reset to zero prior to the start of a
test cycle and is read immediately on completion of
the test cycle.

During normal operation of the test circuit, two-
way measurements and a noise check are made on
each trunk. The computer first calculates the devia-
tion and scores the proper register for the far-to-
near measurement. When the printer completes this
entry, the computer is restored to normal so as to
service the near-to-far measurement in a similar
manner. Should the printer not be functioning, the
control circuit will automatically recycle the com-
puter for the near-to-far calculations. At the end of
a test cycle, the deviation register readings can be
transcribed as the final tally on the data sheet.

Prior to standardization, successful field trials of
the near-end equipment were conducted in the
Washington, D. C. No. 4A toll switching office, in
conjunction with far-end equipment trials in several
other cities throughout the United States. This
equipment is now in production by the Western
Electric Company, and it will greatly aid main-
tenance forces in the analysis of transmission per-
formance of long-distance trunks and will expedite
corrective action by maintenance forces.

R. C. Nance, a resident of Wood-Ridge, N. J., joined the Laboratories in 1936,
and became a draftsman before taking military leave from 1941 to 1945 to serve in
the Signal Corps in the Pacific Theater. Shortly after his return to the Laboratories
he did design work on switchboard trunk circuits and toll crossbar trunk circuits.
In 1953 he became a Member of Technical Staff, concerned with the design of
automatic trunk test frames and associated recording printer circuits for No. 4 and
crossbar tandem offices. More recently his work has involved design of sender test
frames for CAMA toll crossbar installations, Mr. Nance attended evening classes
at Newark College of Engineering to receive the Associate E.E. degree in 1940.

At Bell Laboratories, continuing studies are di-
rected at one of the oldest and most fundamental
problems of the communications industry — the
action of a pair of contacts in an electromechanical
relay or switch as these contacts make or break an
electrical circuit. Thousands of contact operations
may be involved in a single telephone call.

Of special interest has been the phenomenon of
arcing — the discharge of electrical energy when
two contacts are close together. Frequently, arcs
cause welding of the contacts. According to recent
research studies at the Laboratories, it has been
found that welding at relay contacts takes place
the instant the arc is extinguished. This work, by
J. L. Smith and W. S. Boyle, sheds new light on the
mechanism of the welding process.

The process was studied by short-circuiting vari-
ous short lengths of charged transmission line
through an arc formed by closure of a pair of clean
relay contacts. It was found that the contacts tend
to weld at the time when the line has just been com-
pletely discharged. Since the arc is known to pro-
duce a small pool of molten metal on the contact
surface, this suggests that molten metal is drawn
across the contact gap by the redistributed field
after the arc is extinguished, resulting in a weld.
For longer transmission lines or more complex

J. L. Smith (left) and W. S. Boyle studying weld-
ing at relay contacts. The coil and capacitor com-
binations in the center of the picture are simulated
lengths of transmission wire used in the studies.

circuitry, welding is most probable at the instant
the arc is terminated. In such cases, however, termi-
nation is due to a fundamental instablity in the arc
itself. This arises because the diameter of the molten
pool of metal increases as the cube root of the
energy which has been dissipated in the arc, while
the heat losses from the pool increase linearly with
its diameter. In the constant-current arc, therefore,
there occurs a critical time after which it can no
longer be maintained because of the heat losses.

This time of extinction can be computed from the
physical constants of the contact metal and the
current and voltage of the arc. The extinction times
thus computed for several contact materials at vari-
ous voltages and currents agree with the observed
times to weld with a maximum deviation of about
30 per cent.

Prior to these studies, it had been generally be-
lieved that since the volume of molten metal in-
creases with time, welding occurred only after
dissipation of a critical amount of energy and hence
for a critical volume of melt. These studies have
now shown that welding occurs both for much
greater and much smaller energies. Welding time
bears no direct relationship to power dissipated in
the arc, but it is very well correlated with the time
of extinction of the arc.

In addition to providing fast, efficient and economical communications, two
fundamental requirements in the Bell System are safety for telephone users
and employees and uninterrupted service. This applies of course, to the
vast TD-2 microwave radio-relay networks throughout the nation. TD-2
carries a large percentage of the country’s telephone and television trans-
mission traffic, and antenna sites must be protected from damage by light-
ning. Such careful attention has been given to this problem that there has
not been a single injury or service interruption from lightning strokes.

To obtain the height required for line-of-sight
transmission, TD-2 radio-relay stations are located
on hilltops or on tall supporting structures — and
for this reason they are prime targets for lightning.
With about 600 such installations in a microwave
network of some 21,000 route miles, the likelihood
of a thunderstorm occurring over some part of
this vast network is very great. The probable light-
ning-stroke incidence for these 600 structures is
estimated at over 500 per year, which, without
adequate protective measures, would constitute a
considerable hazard to personnel, equipment and
service continuity.

A structure hit by a stroke of lightning becomes
part of the path over which the current passes
between cloud and earth. The magnitude of the
stroke current is principally a function of meteor-
ological conditions and is not significantly affected

by the impedance of the structure. The crest values
of current in lightning strokes vary over a wide
range, as shown by the distribution curve in Figure
1. It may be noted from this illustration that the
average value is about 16,000 amperes, but that
strokes may occasionally reach magnitudes of cur-
rent exceeding 200,000 crest amperes. On the
average, stroke currents rise to peak value in 1 to
2 microseconds and decay to half value in 40 to 50
microseconds. Because of the rapid rate of rise of
the surge front and because of the high currents
involved, inductive potentials of many thousands
of volts can develop, even in structures with neglig-
ible resistance.

Such inductive potentials could cause arcing to
adjacent conducting objects and thus introduce fire
and safety hazards. Where appreciable resistance is
present in the surge path — as might occur at joints

Fig. 1 — Distribution of lightning-stroke currents;
average is about 16,000 amperes, but some strokes
may exceed 200,000 amperes.

and connection points — another fire hazard could
exist from arcing produced by stroke currents of
large magnitude. It is therefore necessary to pro-
vide, between the stroke point and earth, paths
having sufficiently low inductance to limit the build-
up of inductive potentials, and also having adequate
current-carrying capacity to prevent arcing effects.

Fortunately, the antenna towers commonly used
in the TD-2 system are metallic structures having
waveguides and wiring conduits for tower lights
in good electrical contact with the tower at fre-
quent intervals. These parallel paths provide a good
low-impedance path for the lightning currents.

Considerable metal is also present in the equip-
ment buildings in the form of structural members,
reinforcing bars, additional wiring conduits, and
equipment racks, These may be interconnected to
some extent in the normal course of construction,
but more adequate interconnection must be assured
by specific bonding connections. Connections are
established not only between the various conducting
components, but also between them and the area-
grounding structure. The basic approach has been
to simulate as far as economically possible a type
of protective structure known as a “Faraday Cage.”
This is accomplished by means of many conducting
paths and frequent bonding connections.

In the absence of electrical arcing, a surprisingly
small wire (No. 10 AWG copper) will carry most
lightning surges without fusing. It is customary,

mechanical strength, No. 2 copper is employed. To
reduce potential drops due to the impedance of
such conductors, it is preferable to provide multiple
paths to ground for stroke currents, especially with
respect to those parts of an installation housing
equipment and personnel. These factors have been
well recognized in the design of protection for
microwave installations.

The antenna horns employed in the TD-2 sys-
tem are of heavy metal construction capable of
withstanding the fusing effects of a lightning stroke.
When the horn assembly is supported on a steel
tower, which is the most common arrangement,
there is no problem of the electrical conductivity
to earth. Some supporting structures are of con-
crete construction, however, in which case particu-
lar care is taken to provide adequate electrical
conductivity through the reinforcing bars and other
steel members.

The circuits required for aircraft-warning lights
are enclosed in metal conduits supported on the
structural steel of the tower. The topmost fixture
is provided with an “air terminal” in the form of
a 5-foot vertical stainless steel rod to shield the
fixture against direct strokes.

Fig. 2 — Representation of buried-ground network
to protect TD-2 sites from lightning damage.

In a typical installation, the transmitting and
receiving equipment is housed in a building near
the base of the tower. The waveguides from the
horns are electrically bonded at intervals to the
steel tower, and between the tower and the build-
ing such waveguides are supported on a steel rack.
The rack provides additional conductivity in parallel
with the waveguides between the tower and the
building ground.

The grounding arrangement for a microwave in-
stallation is solely for protection purposes, since it
is not required for microwave transmission. Usually,
a buried metallic piping system, such as a water
system, is not available, so it is necessary to con-
struct a “made” ground. Because of adverse ground-
ing conditions at many microwave sites, however, it
is uneconomical to attempt the construction of a
very low-resistance ground. Rather than specify
a resistance value, Bell System practices require
a buried network dimensioned in relation to the
size of the installation. A general idea of such
buried-ground networks is given in Figure 2.

This grounding network — supplemented by bond-
ing connections to the tower footing ground, fuel
tank and other buried metallic objects — effectively
eliminates potential differences around the tower
and equipment building. For high stroke currents,
the area adjacent to the station will attain a high
potential with respect to remote earth, but will not
endanger personnel or equipment within the sta-
tion area. Power and local communication lines
feeding the station will, however, be subjected to
this rise in station potential and will thus require
special protection measures in the form of arresters
on the power conductors and protectors on all com-
munication circuits. The grounding terminals of
these arresters and protectors are all connected to
the station ground ring. Additional protection may
also be provided at intervals on these facilities to

Fig. 3 — J. B. Hays, left, and author discuss results
of Laboratories study of electrical protection.

equalize potentials and to provide an adequate
path to remote ground for a sizeable proportion of
the stroke current.

A final but very important link in this chain of
protective measures is the extensive grounding and
bonding of conduits and equipment racks in the
station to eliminate potential differences in the area
occupied by personnel.

D. W. Bop.e, a native of Huguenot, N. Y., entered the Development and Re-
search Department of the A.T.&T, Co. in December, 1929, where he studied in-
ductive coordination and joint-use problems. He became a member of the Lab-
oratories in 1934. Mr. Bodle’s experience has been chiefly in the field of protec-
tion of equipment against foreign potentials and the protection of personnel from
electric shock, and he has engaged in several field investigations of the character-
istics of natural lightning. During World War II he was concerned with the design
of cathode-ray indicators for airborne radar. Mr. Bodle received a B.S. degree
in Electrical Engineering from New York University. He is a licensed professional
engineer and a member of the A.I.E.E. and of the L.R.E.

In the Automatic Message Accounting system, the two functions of printing
and comparing paper tapes formerly required separate machines. Now,
these two functions are performed by a single AMA unit, which in addition
can automatically scan tapes for special information. The newly developed
AMA printer-comparer-scanner thus increases the efficiency of message ac-
counting procedures and also simplifies the tasks of operating personnel.

The new development resulted from the need
for a simpler means of transcribing AMA perfora-
tor tape information into printed form. During the
early stages of the design it became apparent that
at very little additional cost the machine could
also be made to perform functions of the AMA
tape comparer as well as provide a new require-
ment of tape scanning. The AMA printer-comparer-
scanner combines these functions in a single ma-
chine. The machine, shown in Figure 1, consists of
one bay of relays, one printer cabinet and two read-
er cabinets.

The work performed by the printer-comparer-
scanner can best be understood in terms of what

the AMA system has been designed to do. Included
among the many AMA processing steps are provi-
sions for printing data,* for comparing paper tapes,t
and now, scanning paper tapes. The printing func-
tion is necessary in some instances so that informa-
tion which appears as punched holes in a paper
tape can be recorded in a form readable by ac-
counting personnel. The comparing function is used
in test procedures whereby an AMA paper tape is
compared with a known or standard tape to check
that the equipment is functioning properly. The
new function of scanning provides a method where-
by a tape containing call information may be in-
spected to observe irregularities, answer questions
raised by customers, aid maintenance, or compile
data for the few cases where bills are made out on
irregular dates.

In the initial stages of AMA development, toll-
call rating (calculation of charges for long-distance
calls) was handled manually. AMA call records,

the call was made, were processed through various
AMA machines, and the information necessary to
calculate the charges on each call was assembled
as a single entry on a tape. The AMA printer then
translated the numerical information on the tape
‘into printed letters and numbers and prepared in-
dividual toll slips which were used by accounting
personnel to prepare customers’ statements. The
tremendous growth of long-distance traffic han-
dled by AMA (approximately 32 million toll mes-
sages per month) has made manual methods im-
practical. A present step towards the automation
of toll rating is the use of punched card methods.
This change in method of handling toll calls re-
moves the necessity for the complex AMA printer.
The only call records which must be printed un-
der the present method of AMA operation are the
“straddle” records. This term is significant because
when calls are in process at the time the central
office tape is cut, the records will straddle the cut-
ting point. The assembler-computer will process
the records on each side of the cutting point at
different times and therefore will be unable to per-
form the necessary computations. The assembler-
computer perforates the straddle call records on a
separate tape. Also included on this tape are rec-
ords of calls which exceed the capacity of the as-
sembler-computer for calculating conversation time
or message-unit charges. The tape is printed and
IBM cards are punched manually from the printed
record. The calls are then merged with the rest of
the records for automatic processing. An example
of a straddle record, depicted in Figure 2, shows no
translation of either the calling or called customer’s
office code. The information is printed in the same
numerical form used by the switching equipment.
Another use of the printer is in obtaining mes-
sage-unit summary information for customers who
change or disconnect their lines during the billing
month. In the normal billing procedure, summaries
of the message-unit usage of each customer are
made several times a month and the record is kept
in tape form. A summary tape is prepared for each
central office code. For each customer who has made
any message-unit calls during the period of time
covered by the tape, an entry is made giving the
total message-unit charges which he has accumu-
lated. The entries are arranged in ascending order
of customer line number. These summaries are ac-
cumulated through the billing month and at the
billing date an IBM card is punched from the tape
for each customer, showing his total usage for the
month. This card, together with the cards for toll

messages made by the customer during the month,
is used in making the final bill.

When a customer is to be billed prior to the
regular billing date, however, it is necessary to de-
termine his usage before the cards are punched.
As a normal procedure, a printed record is made of.
the intermediate summary tapes which are pre-
pared during the month. The records are available
when they are needed for billing a particular cus-
tomer without preparing cards for all the customers
in the office.

As a further application of the printer function,
it may be necessary, for maintenance reasons, to
print a verbatim record of an AMA tape. The print-
er-comparer-scanner can do this in either of two
ways. Figure 3 shows a portion of central office
tape printed in the two forms. The form to the left
shows each line printed as it appears on the AMA
tape. The form to the right shows each entry
printed across a single line of the page. When the
“in line” form is used, the zeros, which are always

Fig. 1—The printer-comparer-scanner unit includes a
printer cabinet, left, a bay of relays, center, and two reader
cabinets. Several functions are combined in the machine.

the first digits of a supplementary line, are omitted
from the printed copy. This form is essentially the
same as that used to print straddle records.

The second function of the printer-comparer-
scanner — tape comparing — is used in testing AMA
machines. Since those machines pass intelligence
from one tv another in the form of punched paper
tapes, the machines are best tested by means of
known test input tapes which will produce known
output tapes. The test output tape can then be
checked against a master tape. The printer-com-
parer-scanner checks the two tapes, line by line, for
identity of the perforation. This function was pre-
viously performed by the AMA tape comparer.

The third function of the new AMA unit — scan-
ning — fills a need long felt in the field for a means
of obtaining special information from AMA tape
rapidly and accurately. The alternatives to an au-
tomatic tape scanning device are: using a hand
reader, or printing the entire tape and then scanning
the result by eye. Both of these methods are time
consuming and susceptible to human error. When
the printer-comparer-scanner is used, instructions
required to locate the desired information are set
into the machine on switches and keys located on

Fig. 2 — A typical straddle record with key to iden-
tify each numerical group in the various entries.

Fig. 4— The author introduces into the control
panel information which will initiate the scanning
feature of the printer-comparer-scanner.

the control panel (see Figure 4). When the tape
is inserted, the machine starts scanning the tape a
line at a time until the desired information is found.
The tape moves along at the rate of about eight
feet per minute. When the desired information is
encountered, the machine blocks and sounds an
alarm to attract the attention of the attendant. At
this point, the attendant operates a key to obtain a
printed record of the information.

One possible use of the scanning function pro-
vides an alternative to the printing of the intermedi-
ate summary tapes which was discussed earlier.
When message-unit summary information is re-
quired for billing a particular customer, the four
switches, shown in the lower left row of Figure 4,
are set to correspond to his line number. The tape
containing his record is inserted and the machine
starts scanning at its usual rate of eight feet per

Fig. 5—A_ printed
record of the scanned
tape. Customers’ line
numbers appear in
left column and mes-
sage unit charges ap-
pear in right column,

it encounters either the desired line number or a
higher line number. This feature makes it unnec-
essary to scan the entire tape if there is no entry
corresponding to the desired line number.

As an example, suppose that information on line
number 3953 is desired. All numbers from 0000 to
3952 will be passed over and the machine will stop
on 3953 or, if 3953 is missing, on 3954 or the next
number higher than 3953 which it encounters. Lamp
indications inform the attendant whether the ma-
chine has stopped because the desired number has
been found or because a higher number has been
encountered. Under key control, the customer's
line number and his message units are printed. The
machine can then be reset to scan for some higher
number. A tape containing message-unit summary
information for 10,000 customers can be scanned
in less than half an hour, whereas four hours would

be required to print the complete information. The
printed record is shown in Figure 5. The informa-
tion is arranged in two columns with the customers’
line numbers appearing in numerical order in the
left hand column and the associated message unit
charges in the right hand column.

Many other scanning functions can be performed,
and in every case the procedure is the same. The
required data are set into the machine and the tape
is scanned until the information is found. The ma-
chine can be set to step a message register, instead
of stopping when it encounters the desired infor-
mation, and to continue scanning for subsequent
appearances of the same information. A possible
use of this feature might be to determine the
amount of traffic handled by a given trunk in a
central office. New applications of the printer-
comparer-scanner are continuously being studied.

after receiving her A.B. degree from Vassar College. She has been mainly con-
cerned with AMA development, primarily circuit. design and laboratory testing
of the accounting center machines used in this system. She participated in ac-
curacy tests in 1948 at Philadelphia where the first No. 5 crossbar installation
with AMA was made, and a year later in similar tests when No. 1 crossbar and
AMA were used together for the first time. She also participated in pre-cutover
tests of nationwide customer dialing at Newark and Englewood in 1951. After
a short period devoted to design of crossbar tandem circuits for use with AMA,
she returned to accounting center circuit design work to develop the Printer-
Comparer-Scanner, From 1955 until she left the Laboratories recently, she was
engaged in designing circuits for the Common User Group, part of the air-ground
communication system for SAGE.

The widely acclaimed Bell System Science Series
program, “Our Mr. Sun”, will be telecast in color
over the NBC television network on Sunday, De-
cember 15, at 5:30 P.M., EST (4:30 P.M., CST;
3:30 P.M., MST; and 5:30 P.M., PST). Starring Dr.
Frank Baxter as “Dr. Research” and Eddie Albert
as “Fiction Writer”, the program dramatizes many
facts about the sun and shows scientists at work on
solar studies throughout the world.

First telecast in November, 1956, “Our Mr. Sun”
will be the second in a series of four Bell System

Science programs over NBC-TV for 1957-58. “The
Strange Case of the Cosmic Rays” was seen on
October 25, and “The Unchained Goddess,” a new
program about weather, will be seen on Wednesday,
February 12. “Hemo the Magnificent”, about the
blood and its circulation, will be seen for the sec-
ond time on Sunday, March 16. All four of these
programs were produced and directed by Academy
Award Winner Frank Capra. In addition to their
use on television, these films have been shown to
about six million students in classrooms during 1957.

W. O. Baker, Vice-President in charge of research
at Bell Laboratories, received the honorary degree
of Doctor of Science from Washington College on
October 20. The degree was awarded in Chester-

Dr. Daniel Z. Gibson, right, President of Washing-
ton College, presenting honorary Doctor of Science

town, Maryland, at a convocation marking the 175th
anniversary of the College, of which George Wash-
ington was the first benefactor.

College President Daniel Z. Gibson made the
presentation and cited Dr. Baker as “one of the most
distinguished young scientists of the United States.”
The citation continued by recognizing Dr. Baker
as “an authority on the chemistry of high polymers
and in the development of synthetic rubber. . . . He
has served as visiting lecturer at Princeton, North-
western, Western Reserve and Brooklyn Polytechnic
Institute, is a consultant for the Office of Naval Re-
search and the Army Quartermaster Corps, and is a
member of the Visiting Committee in Chemistry
at Princeton University, and the Science Advisory
Committee of the Executive Office of the Presi-
dent. We are proud to welcome home a native
son and to recognize his distinguished achieve-
ments.”

Dr. Baker was graduated from Washington Col-
lege in 1935 and continued study at Princeton,
where he received the Ph.D.

J. R. Townsend, formerly of the Laboratories and
now special assistant to the Assistant Secretary of
Defense for Research and Engineering, received
one of the highest awards of the American Stand-
ards Association on November 14. He was awarded
the gold Standards Medal at the Association’s An-
nual Award Dinner during the Eighth National
Conference on Standards held in San Francisco.
This Medal is awarded for leadership in the actual
development and application of standards.

With the Bell System for more than 38 years, Mr.
Townsend is a nationally known materials expert
who has been called on frequently to render service
to the highest levels of government. On leave from
Bell Laboratories since 1952, he served as Director
of Materials Application Engineering for the Sandia
Corporation until his recent appointment to the
government post. At the Laboratories, Mr. Town-
send was active in the initiation and promotion of
the materials testing laboratories as well as the
x-ray, optical, welding and metallurgical labora-
tories. Among his many official positions, he has
served as President of the American Society for
Testing Materials and as a member of the A.S.A.
Board of Directors.

The September, 1957, issue of THe BELL SysTEM
TECHNICAL JOURNAL contains the following articles:

Oceanographic Information for Engineering Sub-
marine Cable Systems by C. H. Elmendorf and
B. C. Heezen.

Resistance of Organic Materials and Cable Struc-
tures to Marine Biological Attack by L. R. Snoke.

Dynamics and Kinematics of the Laying and Re-
covery of Submarine Cable by E. E. Zajac.

Theory of Curved Circular Waveguide Contain-
ing an Inhomogeneous Dielectric by S. P. Morgan.

Circular Electric Wave Transmission Through
Serpentine Bends by H. G. Unger.

Cioffi, P. P.— Traveling Wave Tube Apparatus Including
Magnetic Structures — 2,807,743.

Edwards, C. F.— Impedance Matching Devices for Wave-
Guide Hybrid Junctions — 2,806,210.

Archer, R. J., Optical Measurement of Film Growth on Sili-
con and Germanium Surfaces in Room Air, J. Electro-
chem., Soc., 104, pp. 619-622, Oct., 1957.

Baker, A. N., and Webber, D. S., Hydrogen Vibration Spec-
tra of Rochelle Salt, J. Chem. Phys., 27, pp. 689-692,
Sept., 1957.

Burns, F. P., and Fleischer, A. A., Piezoresistive Effect in
Indium Antimonide, Phys. Rev., 107, pp. 1281-1282, Sept.
1, 1957.

Chynoweth, A. G., The Pyroelectric Behavior of Coleman-
ite, Acta Crystallographica, 10, pp. 511-514, Aug., 1957.

Dunn, H. K., and Young, R. W., On the Interpretation of
Certain Sound Spectra of Musical Instruments, J. Acous.
Soc. Amer., 29, pp. 1070-1073, Oct., 1957.

Ellis, W. C., Williams, H. J., and Sherwood, R. C., Evidence
for Subgrains in MnBi Crystals from Bitter Patterns,
J. Appl. Phys., Letter to the Editor, 28, pp. 1215-1216,
Oct., 1957.

Feher, G., Fuller, C. S. and Gere, E. A., Spin and Magnetic
Moment of P® by the Electron Nuclear Double-Resonance
Technique, Phys. Rev., Letter to the Editor, 107, pp.
1462-1464, Sept. 1, 1957.

Feinstein, J., and Kino, G. $., The Large-Signal Behavior of
Crossed-Field Traveling-Wave Devices, Proc. I.R.E., 45,
pp. 1364-1373, Oct., 1957.

Following is a list of the authors, titles and places of publication
of recent papers published by members of the Laboratories:

Fleischer, A. A., see Burns, F. P.
Foster, F. G., see Williams, H. J.
Fuller, C. S., see Feher, G.
Gere, E. A., see Feher, G.

Geller, S., and Gilleo, M. A., The Crystal Structure and
Ferrimagnetism of Yttrium-Iron Garnet, Y,Fe.(FeO,)3,
]. Phys. and Chem. Solids, 3, (Nos. 1-2), pp. 30-36, 1957.

Gordon, J. P., and White, L. D., Experimental Determina-
tion of the Noise Figure of an Ammonia Maser, Phys.
Rev., Letter to the Editor, 107, pp. 1728-1729, Sept. 15,
1957.

Hobstetter, J. N., and Breidt, P., Jr., Detection of Both Va-
cancies and Interstitials in Deformed Germanium, J. Appl.
Phys., Letter to the Editor, 28, pp. 1214-1215, Oct., 1957.

Kelley, E. M., see Williams, H. J.
Kino, G. S., see Feinstein, J.
Kisliuk, P., The Sticking Probabilities of Gases Chemisorbed

Lax, M., Frequency Dependence of the AC Resistance of
Thin Semiconducting Films, Phys. Rev., 107, pp. 650-655,
Aug. 1, 1957.

Matthias, B. T., and Corenzwit, E., Superconducting Alka-
line Earth Compounds, Phys. Rev., 107, pp. 1558-1559,
Sept. 15, 1957.

Matthias, B. T., and Remeika, J. P., Ferroelectricity of Dical-
cium Strontium Propionate, Phys. Rev., Letter to the Edi-
tor, 107, p. 1727, Sept. 15, 1957.

Mertz, P., Information Theory Impact on Modern Communi-
cations, Comm. and Electronics, 32, pp. 431-437, Sept.,
1957.

Pfann, W. G., Techniques of Zone Melting and Crystal
Growing, Solid State Physics, Vol. IV, Academic Press,
New York, 1957.

Romanow, W. J., Crystallographic Angles for Manganese
Bismuthide, |. Metals, 209, p. 1284, Oct., 1957.

Treuting, R. G., and Arnold, S. M., Orientation Habits of
Metal Whiskers, Acta Metallurgica, 5, p. 598, Oct., 1957.

Wernick, J. H., Effects of Crystal Orientation, Temperature
and Molten Zone Thickness in Temperature Gradient
Zone Melting, J. Metals, 9, pp. 1169-1173, Oct., 1957.

Wernick, J. H., and Benson, K. E., New Semiconducting
Ternary Compounds, J. Phys. Chem. Solids, Letter to the
Editor, 3, (Nos. 1-2), pp. 157-159, 1957.

Williams, H. J., Sherwood, R. C., Foster, F. G., and Kelley,
E. M., Magnetic Writing on Thin Films of MnBi, J. Appl.
Phys.. 28, pp. 1181-1184, Oct., 1957.

Wooley, M. C., Passive Components for Submarine Cable
Telephone Repeaters, 1.R.E., Trans. on Reliability and
Quality Control, pp. 14-24, Nov., 1957.

Following is a list of talks given before professional and
educational groups by Laboratories people during October.

Amron, I., Corby, W. J., Craft, W. H., Koontz, D. E., and
Pondy, P. R., A Method of Wide Applicability for Clean-
ing and Etching Electronic Materials.

Burcham, N. P., and Miller, L. E., Stabilization of Germani-
um Alloy Junction Transistor Characteristics Through Sur-
face Treatment.

Closson, H. T., Danielson, W. E., and Nielsen, R. ]., Auto-
matic Measurement of Micro-Deviations in Periodic Struc-
tures,

Early, J. M., and Sevick, J., Characteristics and Structure of a
Diffused-Base Germanium High Frequency Amplifier

Feder, D. O., Craft, W. H. and Koontz, D. E., Simple Tech-
niques for Storing Ultraclean Electron Tube Components.

David, E. E., Jr., Guttman, N., and van Bergeijk, W. A.,
Some Factors Governing the Lateralization of High Fre-
quency Complex Waveforms, (Presented by W. A. van
Bergeijk).

Mason, W. P., and Bommel, H., Frequency and Temperature
Dependance of Internal Friction in Pure Copper.

McSkimin, H. J., Measurement of Dynamic Shear Im-
pedance of Liquids at High Ultrasonic Frequencies.

van Bergeijk, W. A., see David, E. E., Jr.
Weinreich, G., Acoustoelectric Effect in Germanium.

Forster, J. H., and Veloric, H. S., The Effect of Variations
in Surface Potential on Junction Characteristics.

Howard, B. T., Phosphorus Diffusion in Silicon.
Singleton, J. B., and Silverman, S. J., Techniques for Pre-

Smith, K. D., Semiconductor Materials and Processes.
Struthers, J. D., see Bemski, G.

Abraham, R. P., see Kirkpatrick, R. J.
Blecher, F. H., Transistor Feedback Amplifiers.

Hewitt, W. H., and von Aulock, W. H., A Reciprocal Ferrite
Phase Shifter for X-Band.

McDavitt, M. B., 6,000 Mc/Sec Radio Relay System for
Broad-Band, Long Haul Service in the Bell System.

Scheinman, A. H., A Numerical-Graphical Method for Syn-
thesizing Switching Circuits.

Baker, A. N., Recent Developments in Semiconductors, New
York Telephone Company, White Plains, N. Y.

Bashkow, T. R., and Desoer, C. A., Digital Computers and
Network Theory, 1.R.E.-PG Conference on Circuit Theory,
Syracuse, N. Y.

Benson, R, J., Wear Studies of Fine-Pitch Gear Materials,
Semi-annual Meeting, American Gear Manufacturers As-
sociation, Chicago, Ill.

Blecher, F. H., Properties of Junction Transistors, Chicago
Section of I.R.E., Chicago, Ill.

Bleicher, E., Life Testing of Electronic Components, The
American Society for Quality Control, Bridgeport, Conn.

Bradley, W. W., The Sea Bottom as an Environment for
Metals, National Association of Corrosion Engineers, San
Diego, Calif.

Chapin, D. M., Solar Energy and the Bell Solar Battery,
American Society of Mechanical Engineers, New London,
Conn.

Compton, K. G., Sources of Underground Corrosion Poten-
tials, S. E. Regional Meeting, National Association of Cor-
rosion Engineers, Birmingham, Ala.

Dickieson, A. C., Trends in Transmission Systems Develop-
ment at Bell Telephone Laboratories, Tokyo Section of
LR.E., Tokyo, Japan.

Ferrell, E. B., The Control Chart — Modifications and Ex-
tensions, Metropolitan Section of American Society for
Quality Control, Newark, N. J.

Fisher, C. E., Quality Assurance, Waco Section, American
Society for Quality Control, Waco, Texas; San Antonio
Section, San Antonio, Texas; Dallas-Ft. Worth Section,
Ft. Worth, Texas, and South Texas Section, Houston,
Texas.

Galt, J. K., Cyclotron Absorption in Bismuth and Graphite,
Rutgers University, New Brunswick, N. J.

Gause, G. R., The Quality Survey -- An Essential Part of
an Overall Quality Program, Montreal Section of Ameri-
can Society for Quality Control, Montreal, Canada.

Geils, J. W., Research and Development in Industry Today,
Newark College of Engineering, Newark, N. J.

Graham, R. E., Review of Paris Symposium on Physical
Problems of Color Television, Society of Motion Picture
and Television Engineers Convention, Philadelphia, Pa.

Harmon, L. D., Computer Simulation of Pattern Recogni-
tion, Symposium on Pattern Recognition, University of
Michigan, Ann Arbor, Mich.

Harvey, F. K., The Physics of Hearing and Music, New Jer-
sey Division of New York Section, A.LE.E., Allenhurst,
N. J.

Hawkins, W. L., The Behavior of Antioxidants in Autoxida-
tion, Chemical Symposium, Stevens Institute, Hoboken,
N. J.

Hebel, L. C., Jr., Nuclear Spin Relaxation in Superconduc-
tors, 1.B.M. Watson Laboratory, New York City and Phy-
sics Colloquium, Princeton University, Princeton, N. J.

Helm, H. A., The Analysis of Digital Control Systems, Con-
ference on Computers in Control, A.IE.E., Atlantic City,
N. J.

Herbst, R. T., Computer Programing Techniques, 2nd An-
nual Symposium, Piedmont Subsection, L.R.E., Greens-
boro, N. C.

Hornbeck, J. A., Device Research at Bell Telephone Labora-
tories, Joint Session, Tokyo Section I.R.E.-Institute Elec-
trical Communications Engineers of Japan, Tokyo, Japan.

Ingram, S. B., Graduate Training for the Young Engineer at
Bell Telephone Laboratories, 4th General Assembly, Joint
Meeting of the Engineers Council for Professional De-
velopment and the Engineers Joint Council, New York
City.

Ingram, S. B., The Utilization and Training of Engineers in
Industry, Management Division, Cleveland Engineering
Society, Cleveland, Ohio.

Katz, D., Magnetic Regulated Power Supplies, Northern
New Jersey Section, I.R.E., Montclair, N. J.

Laudise, R. A., Hydrothermal Growth of Oxide Crystals,
Conference on Growth and Evaluation of Single Crystals
of Ferrimagnetic Ceramics, Air Force Cambridge Research
Center, Bedford, Mass.

Lawson, C. C., Buried Distribution of Telephone Circuits,
Annual Convention of the Wire Association, Chicago, Ill.

Legg, V. E., Basic Magnetic Components, Northern New
Jersey Section, I.R.E., Montclair, N. J.

Lundberg, J. L., Pyrolyses and Photocyses in the Flash Illu-
mination of Polymers, Chemistry Department Seminar,
New York University, New York City.

MacNair, W. A., Industrial Research and Development, U.S.
Army Signal School, Ft. Monmouth, N, J.

McClure, B. T., Total Ionization by Low Energy Electrons
in Neon, Gaseous Electronics Conference, Cambridge,
Mass.

McMahon, W., Birdsall, H. A., Johnson, G. R., and Camilli,
C. T., Degradation Studies of Mylar, Conference on Elec-
trical Insulation, Pocono Manor, Pa.

Mayo, J. S., Analysis of an On-Off Digital Control System,
Symposium on Feedback Control, A.LE.E., Atlantic City,
N. J.

Moore, E. F., A General Introductory Survey of Automata,
Informal Seminar on Automatic Computers and_ their
Capabilities, University of Pennsylvania, Philadelphia, Pa.

Moore, G. E., Physics in Industrial Laboratories, Physics
Club, Fordham University, New York City.

Morrison, J., Gas Collection and Analysis System Employed
in Vacuum Tube Problems, 1957 4th National Vacuum
Symposium, Boston, Mass.

Nielsen, J. W., The Use of Molten Lead Oxide as a Solvent
for Magnetic Crystals, Symposium on Crystal Growth, Air
Force Cambridge Research Center, Bedford, Mass.

Pierce, J. R., Fancies and Fallacies of Space Travel, Joint
LR.E., A.LE.E. and American Rocket Society, New York
Section, New York City; Griffiiss Air Force Base Club,
Rome Air Development Center, Rome, N. Y.

Pierce, J. R., The Challenging Field of Engineering Writing
and Speech, 1st National Symposium, I.R.E.-PG on Engi-
neering Writing and Speech, New York City (Presented
by H. S. Black).

Pfann, W. G., New Methods of Purifying Solid Materials,
Stuyvesant High School, New York City.

Pollak, H. O., The Problem of Minimal Connecting Net-
works, Computation Laboratory, National Bureau of
Standards, Washington, D, C.

Schawlow, A. L., The Intermediate State of Superconduc-
tors, Physics Colloquium, Johns Hopkins University, Bal-
timore, Md.

Schroeder, M. R., Artificial Stereophony Using Single Input,
1957 Convention of the Audio Engineering Society, New
York City.

Scovil, H. E. D., The Solid State Maser, PGMTT, PGED
and Northern New Jersey Section, I.R.E., Murray Hill,
New Jersey.

Sharpe, L. H., Electrolytic Regeneration of Cupric Chloride
Etching Solutions, Joint Bel! Telephone Laboratories-
Western Electric Company, Printed Wiring Symposium,
Greensboro, N. C.

Sobel, M., On a Nonparametric Definition of the Represen-
tativeness of a Sample with Tables for Applications, Co-
lumbia University, New York City.

Stephens, Miss S. J., Preparation and Properties of Clean
High-Area Metal and Alloy Evaporated Films for Use in
Surface Studies, 4th National Vacuum Symposium, Boston,
Mass.

Warthman, K. L., Bell Telephone Laboratories Optical
Tracking System for NIKE Radar, Society of Motion
Picture and Television Engineers, Philadelphia, Pa.

Weinreich, G., Acoustoelectric Effect in Germanium, Physics
Colloquium, Yale University, New Haven, Conn.; Uni-
versity of Minnesota, Minneapolis, Minn.

Wenk, H. A., Trips toe DEW Line and White Alice, Mountain
Lakes School, Mountain Lakes, N. J.

Wilkinson, R. L, Some Engineering Applications of Queue-
ing Theory, Administrations Applications Conference,
American Society for Quality Control, Columbia Uni-
versity, New York City.

Wintringham, W. T., Tailoring a Facsimile System to Its
Application, Savings Bank Research Group, New York
City,

Wright, S. B., Life Along the DEW Line, Circa 1957, St.
Cloud Presbyterian Couples Club, West Orange, N. J.
(Presented by R. C. Newhouse. )

Younker, E. L., Storage Devices: Characteristics and Tech-
niques, 2nd Annual Symposium, Piedmont Subsection,
LR.E., Greensboro, N. C.

One method of thermo-compression bond-
ing. A heated wedge presses a wire against a
heated semiconductor with enough force to
deform the wire. Adhesion occurs in seconds.

Thermo-compression bonding pro-
vides a new way to attach a wire
to a semiconductor. It calls for
heat and pressure — nothing else.
The wire and the semiconductor
are moderately heated, then pressed
together under moderate pressure.
The resulting bond is very strong—
stronger actually than the wire. No
chemical flux or molten metal is
required.

Eliminating molten metal pro-
vides an enormous advantage in
fixing electrical connections to
transistors. That’s because molten
metal tends to spatter and spread
uncontrollably over the surface of
a semiconductor. And it may alloy

Wire bonded to germanium by thermo-compression technique (en-
larged). Wires only 1/10 the breadth of a human hair have been
successfully anchored to germaniun) wafers only three hairs thick.
The bond may be an ohmic contact or rectifying contact by adding —
suitable impurities to the wire and the semiconductor.

with the semiconductor to alter iis
all-important crystalline structure
and chemical purity. Thermo-com-
pression bonding easily and quickly
makes a strong permanent electri-
cal connection without damaging
the semiconductor. Furthermore,
the lead may be attached to micro-
scopic areas and precisely posi-
tioned, a most valuable aid in the
construction of high-frequency
transistors.

Thermo-compression bonding
will speed the production of tran-
sistors . . . the transistors needed to
fill all the new jobs Bell Labora-
tories finds for them in the quest
for still better telephony.

At Bell Labs Howard Christensen and
Orson Anderson discuss their discov-
ery of new bonding principle with
Peter Andreatch, Jr., who collaborated
in the studies.

Bell Laboratories Record  1957-12: Vol 35 Iss 12