POWER LINE TREATMENT FOR THE MI CARRIER TELEPHONE
SYSTEM, J. M. Dunham... 2
PORTABLE MICROWAVE TOWER...
TELEPHONE SERVICE FOR TRAINS, N. Monk . . . . .
A NEW CRYSTAL CHANNEL FILTER, E. S. Willis . 18
HISTORIC FIRSTS: RADIO ALTIMETER. . . |S

AUTOMATIC SWITCHING FOR PRIVATE-LINE TELETYPEWRITER
WAVEGUIDE HyBRIps, W. A. Tyrrell. . .
MODELS 65 AND 66 HEARING Alps, J. R. Power. . . . . 80

A PORTABLE TOWER HAS BEEN DEVELOPED TO SURVEY BY MICRO-
WAVES THE ROUTE FOR RADIO RELAY SYSTEMS (SEE PAGE 6)

BELL TELEPHONE LABORATORIES INCORPORATED
463 WEST STREET, NEW YORK 14, N. Y.
0. E. BUCKLEY, president J. W. FARRELL, secretary W. ©. BURGER, treasurer

PHILIP C. JONES, science editor R. LINSLEY SHEPHERD, associate editor
HELEN McLOUGHLIN, assistant editor LEAH E. SMITH, circulation manager

As 1947 draws to its end, we can look back on it as a year
of outstanding progress. Enthusiasm combined with hard
work has produced imposing results. Projects interrupted by
the war have been pushed to completion. Projects started
since the war are now coming through. The birth rate of new
ideas has been high, and the further we go the more oppor-
tunity looms ahead.

But we are not content with what we have done, and enter
1948 with a determination to mark the year with accomplish-
ments that will surpass anything we have done in the past.

My grateful appreciation goes to all the members of our
Laboratories family who have worked together so harmo-
niously and successfully, and my best wishes are for a New
Year as happy as it is sure to be productive.

Power lines over which M1 carrier sys-
tems* are operated usually start from a
sub-station and extend with branches and
sub-branches through their service territory
to supply power to the scattered customers.
For the most part, the lines are single
phase with a multi-grounded neutral, and
operate at about 7,200 volts, 60 cycles.
Transformers near the customers’ houses
reduce the 7,200 volts to the usual 120-240
voltage for lighting and power, but unfor-
tunately, these transformers have a high
attenuation for the M1 carrier-frequency
currents. The simple expedient of plugging
a suitable carrier-telephone set into a 120-
volt outlet in the house thus cannot be uti-
lized. A different method of coupling the

The coupling device employed consists
of a high-voltage capacitor connected in
series with a coil which is grounded, as
shown in Figure 1. Telephone carrier
equipment is connected across this coil. At
power frequencies, the impedance of the
capacitor is about 1.5 megohms, whereas
that of the coil is about 3 ohms. Thus the
normal 60-cycle voltage on the coil is only
a small fraction of a volt. Abnormal volt-
ages, which would otherwise appear across
the coil if the capacitor failed or if the coil
winding developed an open, are prevented
by protector blocks across the coil and a
high-voltage fuse in series with the capaci-
tor, which insure prompt clearing of a dam-
aged capacitor or the by-passing of an
opened coil. A switch is provided in the
coupler box which by-passes the coil and
protector blocks, so that the blocks may be
safely removed for inspection or the coil
may be replaced. The coupling capacitor
and l-ampere fuse are shown in Figure 2,
and a typical pole installation for a sub-
scriber is shown on this page. The coupler
box is shown in Figure 3. The coils shown
in Figure 1 are in the larger of the two
cans immediately above the terminal strip,
while most of the other apparatus of the
unit consists of filters.

The coupling capacitor consists of an oil-
impregnated paper capacitor unit con-

Typical pole installation at the end of a carrier
section showing a tap choke at upper right to
block the carrier from the line beyond this
point. A fuse and coupling capacitor are at the
upper left, and a coupling unit below all the
power equipment. The power transformer with
lightning arrester mounted on it is at the level
of the neutral wire

tained in a glass tube about 16 inches long
and 2 inches in diameter. It has a capaci-
tance of 2,000 yyf, and a maximum rated
60-cycle operating voltage of 8,700, but it
must withstand impulse tests at 95,000
volts to conform with A.I.E.E. standards
for this type of power equipment.
Efficient transmission of carrier over the
power line requires proper terminations at
the ends of lines and choke coils at taps to
reduce reflection losses. Early field tests in-
dicated the approximate inductances that
should be used for the chokes. Three types
of coils are specified: isolating, tap and
transmission chokes. Although both the iso-

GROUND WIRE
Fig. 1—Circuit schematic of the 60-cycle section of
a coupling unit

Since all of these chokes operate at 7,200
volts to ground and carry the power-line
current, they must meet the same require-
ments as similar power-line equipment for
short-circuit currents, temperature rise due
to load currents, and protection against
lightning voltages. These requirements tend

Fig. 2—Coupling capacitor and fuse used for
connecting low-voltage carrier circuits to the
high-voltage power lines

to conflict with those for carrier frequen-
cies. Large current-carrying and heat-dissi-
pating ability, for example, conflict with
the objective of low winding capacitance.
This imposed rather severe design prob-
lems. The three types of chokes are de-

signed to withstand 500 amperes short-
circuit current. Suitable gaps are provided
on the coils for lightning protection.

The rated continuous power-line load
current for the isolating chokes is 10 am-
peres, and they will carry up to 15 amperes
continuously without undue heating. This
choke coil is mounted in an oil-filled steel
tank having two high-voltage porcelain
bushings, as shown in Figure 4. The assem-
bled coil, which weighs sixty pounds, is
mounted on the power pole and connected
in series with the power line.

The tap choke and the two transmission
chokes are not oil-filled; they are rated at 4
amperes, but will carry up to 7, 9 and 10
amperes, respectively. A coil of this type
with supporting clamp is shown in Figure
5. It is suspended by means of its clamp
from a pin-type power insulator. The coils
are designed for hot-line mounting; that is,
they can be put in place with an insulated

hot-line stick and connections made with-
out interrupting the 7,200-volt circuit.

Where load currents at either end of a
carrier section exceed 15 amperes, two iso-
lating chokes may be connected in parallel.
Tap chokes are not operated in parallel be-
cause 2.5 mh is about the minimum induc-
tance which will effectively block these
carrier frequencies. If tap lines have cur-
rents greater than 7 amperes, therefore, an
isolating choke can be installed in place of
the tap choke.

Some rural power lines are equipped
with automatic reclosing circuit-breakers to
restore service on the line following trouble,
and the winding of the operating solenoid
is connected in series with the line. These
coils insert a large loss in the line at carrier
frequencies, and so, when there are circuit-
reclosers in a carrier section, it is advisable
to by-pass the solenoid coil with an imped-
ance that is low at carrier frequencies, but
high compared with the coil impedance at
power frequencies. The by-passing unit, de-
signed for mounting inside the oil tank of

the circuit recloser, has a maximum imped-
ance of 50 ohms at carrier frequencies.

In applying the M1 carrier telephone sys-
tem to a rural power line, the equipment
mounted on power-line poles is installed by
power linemen, except the common termi-
nal and cabinet, which are installed by
telephone linemen after power-line equip-
ment connections have been made. Since
telephone linemen must have access to the
coupler boxes on the pole, they are located
at least 40 inches below any power-line
equipment. Drops are run from these boxes

Among the more recent plant develop-
ments is this new UG distribution wire de-
signed for burying in the ground. Perfected
by the Laboratories and now used by a
number of Bell companies, the wire con-
sists of a pair of sixteen-gauge copper con-
ductors covered with rubber insulation,
over which is a braided steel wire armor.
The outside jacket is of neoprene. The in-
creased tensile strength of the wire results
in fewer breaks and, with the armor act-

The choke coils were designed by S. G.
Hale and are being manufactured by the
Western Electric Company. The coupling
capacitor now being used, shown in Figure
2, was designed by the Sprague Electric
Company to meet requirements set up for
the M1 carrier telephone system. Specifica-
tions and acceptance test requirements for
the coupling capacitor were prepared by
J. R. Weeks, Jr., and C. C. Houtz.

THE AUTHOR: J. M. Dunnam received a B.E.E.
degree from Ohio State University in 1924. After
two years with the Commonwealth Southern Cor-
poration he joined the D & R, where he worked
on low-frequency induction as a member of Project
Committee 2J of the Joint Subcommittee on De-
velopment and Research, Edison Electric Institute
and Bell System. During World War II, he was
associated with the development of radar equip-
ment for certain fighter planes. Subsequently he has
been concerned with the power-line equipment
and protection features involved in adapting rural
power lines for M1 carrier and also with low-
frequency inductive coérdination problems.

ing as a shield against lightning, no sepa-
rate shield wire is necessary. The armor
and jacket provide additional protection
against cutting and crushing during instal-
lation and in service. This new wire is
used in place of open wire or cable in
rural areas where soil conditions permit. It
is also excellent in outdoor locations where
tree interference exists. W. K. Oser of Out-
side Plant Development was the engineer
on this project.

Since microwaves follow a line-of-sight
path, one of the preliminaries to setting up
a system is to assemble a set of topographic
maps and pick out a series of suitable hill-
tops. But there might be a steel silo or

With the tackle fastened to the bottom of the lowest
section, and with a long lever on the winch handle, the
whole tower is lifted. The method of placing each section
in the hoisting yoke is shown on the cover of this issue

water tank right in line; and in the plains
country there are no hills to give a view
along the radio path. So, as a preliminary
to laying out the Chicago-New York radio
relay system, the Laboratories have devel-
oped a tower for quick erection and a mi-
crowave transmitter and measuring receiver
to go with the tower. With this outfit, the
path can be surveyed by radio waves.
Noteworthy advantage of these towers

over any heretofore built is that the erect-
ing crew work entirely at, or very near,
ground level; thus professional riggers are
not required and the hazard of working far
above ground is eliminated.

The tower is lowered onto the added section and
bolted to it; tapered bushings in the ends of the pipes
hold the two sections in alignment. As the tower goes
up, additional guys are added every six sections

First step in putting up the tower is to
level off a few square feet of firm soil, then
lay down a base plate and set on it the
erection frame seen in accompanying illus-
trations. Inside the frame is placed the top
section of the tower. It carries a commu-
nication antenna and its lead-wire; a pair
of pulleys carrying a loop of light steel
cable, and four guy cables.

by hand, and the second section placed
under it. But from then on, as shown in the
illustration on the cover of this issue, a
hoisting yoke is fastened to the bottom of
each section and the whole tower is raised
vertically upward. Guy anchors are placed,
unless trees are available, at a distance
from the tower suited to the final height,
and a workman at each point tends a winch
to pay out the guy cable as the top of the
tower rises. When the tower has been lifted
high enough, the erection frame is opened;

With all connections made, the receiver starts
on its dizzy voyage. Left to right, G. H. Baker,
G. M. Phillips and H. G. Fisher

and another section is put on the base
plate. The tower is then lowered an inch or
two until tapered bushings have engaged
the ends of the four uprights; then the two
sections are solidly bolted together and
the hoisting yoke is shifted to the bottom
in readiness for another lift.

As the tower goes up, additional guys are
added every six sections (48 feet). When
the desired height is reached—which may
be as much as 200 feet—the erection frame
is removed; a rolling carriage is put in

The “dish” can be oriented in azimuth and
elevation. Transmission is measured at various
heights to determine a clear path

Microwave measuring equipment and antenna controls,
left; on the table is the v.h.f. communication set

place on one side of the tower frame-
work, and a hand-operated hoisting drum
is attached. The microwave transmitter (or
receiver) is attached to the carriage and
two electrical cables are connected to it.

With the winch, the carriage is raised while
the two cables are being paid out from
their reels. When the desired height is
reached, the inboard ends of the cables,
which have been stowed inside the reels,
are unrolled and led to the apparatus
shown in the illustration at the left.

Electrical equipment consists of a micro-
wave oscillator with antenna at one end of
the path to be surveyed, and a receiver-
detector-meter set at the other end. To
line up the transmitting and receiving an-
tennas, each is provided with two motor
drives; one can swing the “dish” through
180 degrees in azimuth and the other
through 5 degrees in elevation. There is a
two-way radio communication set similar
to those used for mobile radio. Power for
all equipment, including night lights for
airplanes, comes from duplicate gasoline
alternators at each end, which deliver 115-
volt, 60-cycle, a-c.

The tower was designed by R. R. Andres
and A. H. Lince of Transmission Equip-
ment under the supervision of T. J. Grieser.
The electrical system was designed by
G. M. Phillips and G. H. Baker of Trans-
mission Engineering under the supervision
of J. M. Barstow.

High-frequency induction furnace in the
Metallurgical Laboratory at Murray Hill.
O. J. Barton is shown removing slag and
cleaning out the crucible after pouring a
heat in preparation for the next experi-
mental melt

On August 15, Bell System radio tele-
phone service became available to pas-
sengers on certain trains of the Baltimore
& Ohio and Pennsylvania Railroads op-
erating between New York and Washing-
ton. This radio extension of telephone
service—being operated only experimentally
at the present time—has been made feasible
by the recent installation of the urban mo-
bile radio system* in many of the larger
cities. The same mobile receivers and trans-
mitters are used, and all calls pass through
the mobile service operators in the city
nearest the train when the call is made.

On the Baltimore & Ohio Railroad,
the equipment is installed in the club car
on the “Royal Blue,” which makes one round
trip between the above points daily. On
the Pennsylvania Railroad, it is located in
the club car on both the northbound and
southbound “Congressional Limiteds.” Since
these cars return northward on the “Presi-
dent” and southward on the “Speaker,” the
service will be available on these trains
also in the directions indicated, as well as
on the “Congressional Limited” in both
directions. In the vicinity of New York,
calls are completed through the Newark
mobile service operator. After the train
passes out of range of the Newark station,
the calls are handled through Philadelphia,
Baltimore, or Washington as the train
passes into the areas within the range of
these stations. Since, at the time the service
was inaugurated, no one radio frequency
was used for urban mobile service at all
four of these cities, each train is provided
with two sets of radio equipment so that
communication can be established on either
of two channels as desired.

Fig. 1—William R. Triem, General Superintend-
ent of Telegraph of the Pennsylvania Railroad,
placing a call from the telephone booth on the
lounge car “John Adams” with the recently
installed mobile radio telephone apparatus

with the aid of the cabinet shown in Fig-
ure 2, which is called Control Unit B. On
its face, this unit has a lock to prevent un-
authorized use of the equipment, a key to
select either of the two channels available,
and a three-position switch to permit the
attendant to talk to a mobile operator or
to the occupant of the telephone booth, or
to connect a call through to the booth. In
addition, there are a number of supervisory
lamps and buttons for turning the trans-
mitter on and for signaling the booth. The
relays required for the switching operations
are mounted in Control Unit A, which is
installed with the radio equipment.

In the usual mobile system, the handset
in the vehicle is equipped with a button
which is pressed for talking and released
for listening. This permits a single antenna
to be used both for transmitting and re-
ceiving; the antenna is switched to either
the transmitter or receiver by the action of
the press-to-talk switch. Since only one
person or a very few people use the equip-
ment in each mobile installation, they soon
get accustomed to operating the press-to-
talk switch.

For train telephone service, on the other
hand, those using the telephone will for
the most part not be familiar with press-
to-talk operation, and thus the equipment
on the trains has been modified to permit
the handset to be used in the ordinary
way. This is accomplished by using two
antennas—one at one end of the car for
the transmitter, and one at the other end

Fig. 3—Train telephone operator, Miss Helen K.
Reese, at the control point for the mobile radio tele-
phone ‘service in Pennsylvania lounge car “John
Adams.” At her right is the Control Unit B shown
in Figure 2. The window just to the right of the
handset mounting opens to the telephone booth
on the other side of the wall

Fig. 4—A. S. Hunt, Chief Engineer of Communica-
tions and Signals of the B. & O., talks over the
attendant’s telephone in the lounge car of the
B. & O.’s “Royal Blue”

Fig. 5—Installing one of the antennas on the Pennsyl-
vania Railroad lounge car “John Adams.” J. L. Lindner,
Bell Telephone Laboratories, at the left, and G. E.
Goldner of The Diamond State Telephone Company

and 388A radio receivers{ operating from
12 volts d-c are employed on the trains,
there being two transmitters and two re-
ceivers on each car. The 12-volt source
in each installation is supplied by the rail-
road from a specially installed 12-volt stor-
age battery. This battery is charged when
not in use from the regular 32-volt car
battery through suitable voltage dropping
and regulating equipment. The 12-volt bat-
tery is connected to the radio equipment
through a small power panel which con-
tains a disconnect switch and fusing equip-
ment. A large part of the design work for
the circuits and equipment was carried
on by H. S. Winbigler, while the two con-
trol units together with the power panel
and coaxial filter previously mentioned
were produced in the Graybar-Varick
Model Shop under the direct supervision of
C. P. Bartgis.

A block schematic of the arrangement
employed in each car is shown in Figure
6. The radio sets, filter, power panel, and
Control Unit A are mounted together. On
the Baltimore & Ohio Railroad, these
units are contained in a built-in compart-

RECEIVING TRANSMITTING
ANTENNA ANTENNA
COAXIAL
FILTER
=
RADIO 2 > RADIO
RECEIVERS TRANSMITTERS
-----5
r
i
A B
CONTROL
UNITS
'
POWER
Fig. 6—Block schematic of the
telephone circuit on the train == ATTENDANT PASSENGE

ment next to the passenger booth. On the
Pennsylvania, a special equipment cabi-
net is mounted in the interior of the car
near the attendant’s position, as shown in
Figure 7.

The operation of the telephone service
on the Baltimore & Ohio Railroad is un-
der the supervision of The Chesapeake and
Potomac Telephone Company of Baltimore,
while that on the Pennsylvania is handled
by The Bell Telephone Company of Penn-
sylvania. Since the trains lie over at night
in yards outside the territories of these
companies, maintenance assistance is be-
ing furnished by several other Bell System
operating companies.

Fig. 7—Transmitters, receivers, and power sup-
ply for the mobile telephone equipment on
Pennsylvania Railroad trains are installed in
a single cabinet

THE AUTHOR: Newron Monx interrupted his
college work at Harvard to spend two years with
the Signal Corps during World War I. After grad-

uating with an A.B. degree in 1920, he entered
the Harvard Engineering School, from which he
received the B.S. degree in Communication Engi-
neering in 1922. He then joined the Department
of Development and Research of the American
Telephone and Telegraph Company, where lis
early work was concerned with interference preven-
tion investigations. Later he became interested in
carrier development, and continued this work after
transferring to the Laboratories in 1934. Just prior
to World War II, he devoted most of his time to
applying carrier equipment to railroad communica-
tion systems. During World War II he was active
in the development of voice-frequency and carrier
systems for the Signal Corps. Since the war, he
has been in charge of a group developing radio
for railroads and airplanes.

Since their development in the years be- that could be produced in relatively large
fore the war, broadband carrier systems quantities more economically than the orig-
have come steadily into more extensive use, inal design. These new 219-type channel
and modifications have been made in their filters, such as shown in Figure 1, require
circuits and apparatus as advances in the less than two-thirds as much mounting
art have made them desirable. One such space as the earlier 75-type filters.
More compact than the earlier design,
the configuration of the new filter also re-
quires fewer coils and capacitors. This type
of filter is critical of adjustment, and the
desired performance is realized only if the
electrical characteristics of the component
elements are maintained close to their theo-
retical values. Hence, it is only with the -
development of the more precise wire-sup- q
ported crystal unit replacing the clamp-
type crystal unit that it has been possible
to utilize this type of filter configuration.
The new filter consists of only one lattice-
type section in contrast to two in the earlier

Fig. 2—The new 219-type filter, at the left, requires
only two-thirds the mounting space of the former 75-
type filter shown at the right

advance was the wire-supported, hermeti-
cally sealed crystal* unit replacing the pre-
vious clamp-type construction. These new
units are not only more economical in the
space they require, but also they can be
more precisely adjusted for effective induc-
tance and resonant frequency. It was these
features that offered an opportunity to de-
velop a new channel filtert of reduced size

design. The four coils used in the old filter
are replaced by two less expensive coils in
the new design, and four of the capacitors
are omitted. These differences, and the re-
sulting decrease in size, are evident in Fig-
ure 2, where the new filter is at the left and
the old one at the right.

In the 75-type filter there was one crystal
connected electrically in each of the four
branches of each filter section, and thus
eight crystals in all. The two crystals in the
series branches of one section, however,
had the same resonant frequency. This was

also true of the diagonal branches of the
same section, but the series branch reso-
nance differed from the diagonal branch
resonance, and the resonances for the cor-
responding arms of the two sections dif-
fered. Four resonant frequencies were thus
required for the two sections. Since the
coating on each side of the crystal plate
was divided into two parts, and thus each
plate became electrically two crystals vi-
brating in unison, only four plates were re-
quired in each filter to provide the eight
crystals required in the electrical design.
Likewise, the new filter also employs eight
crystals with four resonant frequencies. In
effect, it incorporates the two lattice sec-

parallel in each of the four branches, as
shown in Figure 3. The two crystals of each
sealed crystal unit are connected in differ-
ent lattice branches, as indicated by the
markings f,, f., f, and f, of Figure 3, where

Figs. 4 and 5—The four glass-sealed crystal
units are cemented into a rectangular molded
base. The eight elements of these units forming
a filter are interconnected in the base to two
input and two output leads

the two crystals of the same unit are sep-
arated to bring them into the branches of
the filter into which they are connected.
The four glass-sealed crystal units that
provide the basis of the lattice structure
are mounted at the corners of a rectangular
molded base, as shown in Figure 4. Four
leads from each unit pass through the base
and are interconnected, as shown in Figure
5. In Figure 6, where the same frequency
markings are used as in Figure 3, the inter-
connections are shown schematically. Two
input and two output leads are brought out
from the interconnected points. The molded
base of the crystal unit is fastened, in turn,
to one side of a metal plate forming the
chassis of the filter, as shown in Figure 7.

On the other side of the plate are mounted
the capacitors and resistors associated with
the crystal units. As will be noticed from
Figure 3, there are three adjustable capaci-
tors: a double capacitor adjusting the ca-
pacitances in one series and one diagonal
branch differentially, and two single capaci-
tors—one at the input and the other at the
output of the lattice. These are the three
elements mounted on the upright base, as
evident in Figure 7. The fixed capacitors
and the resistors associated with the coils
are mounted on the bottom of the chassis.

The inductances shown at the ends of the
filter in Figure 3 are air-core coils mounted
in the cylindrical copper containers, evident
in Figure 7. The high coil-impedance called
for by the filter design requires that the
parasitic capacitances between the wind-
ings, and between the windings and case, be
kept as small as possible. This is accom-
plished by winding the coils in four sec-
tions, as shown in Figure 8.

A reactance-frequency diagram for the
filter is shown in Figure 9, where the reac-
tance of the series branches is shown solid
and that for the diagonal branches, dashed.
The pass-band for the filter spans the re-
gion where the reactances of the series and
diagonal branches are of opposite sign,

Fig. 6—Interconnections for the eight elements of
the four crystal units incorporated in the filter. Fre-
quency markings are the same as in Figure 3

A lattice-type filter section is a “bridge”
circuit, as indicated in Figure 10, and when
the reactances of all branches are alike,
both in magnitude and sign, the bridge is
balanced, and no energy from the input
gets through to the load. Over the pass-
band this balance never exists, as evident
from Figure 11, but beyond the pass-band
it exists whenever the reactance of the se-
ries branches equals that of the diagonal
branches in magnitude. In the attenuating
region, the reactances are always alike in
sign, as evident from Figure 9. In this latter
diagram, the series and diagonal branch
reactances are shown equal except for a
short distance just beyond the pass-band,
but if the curves had been drawn to a
larger scale, the two reactances would be
seen to cross and recross each other—never
departing very much, but exactly alike only
at isolated points. At each crossing point
there is a peak of attenuation due to bal-
ance of the bridge circuit, while between
peaks the attenuation depends on the sep-
aration of the curves of reactance for the
series and diagonal branches, the greater
the separation, the lower the attenuation.

Fig. 7—The 219-type filter showing capacitors and re-
sistors associated with the crystals and coils of the
filter. The coils for the input and output of the filter
are in the cans at each side of the crystal units

Fig. 8—To reduce parasitic capacitances, the air-core
coils are wound in four sections

tances and resonant frequencies of the crys-
tal units is required to accurately control
the location of these crossings and the sep-
arations of the two reactance curves. The
required accuracy could not be attained.
with the clamp-type crystal units; hence, it
was not until the wire-supported crystal
unit was developed that this compact type
filter design could be utilized.

In referring to the “bridge” balance of
the four reactance branches, only reactance
was mentioned because the arms are pre-
dominantly reactive. Associated with each
of these reactances, however, there is some
dissipation, and to obtain a high peak loss
in the filter at a definite frequency, there
must be a balance of the conductances of
these four branches as well as of their re-
actances. Conductance unbalance of these
branches in the attenuating region of the
filter will degrade filter performance to the
same extent as reactance unbalances.
Whereas the tuning of the differential con-
denser balances these reactances at one fre-
quency, no means is provided for balancing
the conductance component. Extreme care
must be exercised, therefore, to keep these
four branches alike. Even though the crys-
tal units are surrounded by dry air and en-
closed in sealed glass containers, it is still
necessary to protect the filter against atmos-
pheric conditions of high relative humidity.
A trace of salt or other contamination
across the terminals in the molded base of

Fig. 10—The four branches of a lattice-type filter,
shown at the left, form a bridge circuit as indicated

Fig. 11—Insertion-loss frequency characteristic of the
219-type crystal channel filter

the crystal units or across the ceramic in
the air capacitors will make the insulation
resistance highly sensitive to the moisture
in the adjacent air and may result in large
conductance unbalances in the lattice. To
guard against this condition, only homoge-
neous low-loss materials are used for the
insulating materials within the lattice struc-
ture. The insulating parts assembled in the
filter are kept clean, and the filters are ad-
justed, tested and sealed hermetically when

THE AUTHOR: E. S. Wits joined the Technical
Staff of the Laboratories in July, 1927, after re-
ceiving the degree of M.A. from the University of
Missouri. Since then he has been engaged in the
development of various types of transmission net-
works, such as electric wave filters and equalizers.
He had an active part in the first use of quartz
crystal elements as applied to various types of filter
circuits. In the past few years he has been chiefly
engaged with problems associated with the crystal
channel filter for broadband carrier systems. Re-
cently, this work has involved the application of
synthetic crystal units to filter circuits.

surrounded by an atmosphere in which the
relative humidity is not greater than 40
per cent.

The 219-type crystal channel filter is the
first commercial application of lattice-type
filter circuits in which more than one crys-
tal unit is used in each branch of the lattice.
The economies it permits in space, material
and labor are very desirable in view of the
increasing use of broadband carrier sys-
tems in the telephone plant.

At the Chester field laboratory, J. H.
Shuhart is preparing a test of various line-
wire materials to study their fatigue prop-
erties under vibrations induced by winds
January 1948

While struggling with the problems of
long-distance telephone lines during the
early teen-age years of this century, Bell
System engineers were considerably ham-
pered by the reflection of electrical waves
at impedance irregularities along the line.
These electrical echoes proved serious ob-
stacles, particularly to the application of
repeaters, and for a long time limited their
use in circuits. The objectionable charac-

One of the antennas used with the terrain
clearance indicator. These antennas were at-
tached to the under side of the plane as shown
—one to transmit and one to receive

teristics of echoes on telephone lines was
intimately associated with the distance be-
tween the points of origin and reflection.
In fact, the effect of the echoes in produc-
ing a “humpy” impedance-frequency curve
had been used by telephone engineers to
measure this distance, and thus locate the
position along the line of a defective load-
ing coil or other “irregularity.”

The, work that had been carried on, and
the precision and beauty of the reflection
phenomena, suggested to Lloyd Espenschied
that electrical reflections had merit in their
own right, and that they could be put to
more positive use. One of the early appli-
cations that occurred to him was as a
warning and safety system for railways.

His proposal was to send an electric wave
along the track ahead of the locomotive.
A broken rail or another train would form
an impedance irregularity that would re-
flect the wave, and the arrival of the re-
flected wave at the locomotive would not
only give warning of danger ahead, but
would permit the distance to the danger
to be determined and the train automat-
ically controlled. A patent on such a system
was applied for in 1919, and patent No.
1,517,549 was granted in 1924. Among the
early ideas entertained at the time was that
of the use of a frequency-swing oscillator
and beat-frequency reception for indicat-
ing the distance — principles later used in
the radio altimeter.

A number of allied and modified sys-
tems were devised in the immediately fol-
lowing years, but meanwhile the airplane
was rapidly assuming an important posi-
tion in the transportation field, and an elec-
trical reflection system that would give an
airplane a continuous indication of its
height above ground seemed highly desir-
able. Barometer readings, the only indica-
tions of distance available for this purpose
heretofore, gave the height above sea level,
and thus were of little use when the ele-
vation of the land beneath the plane was
increasing rapidly, as when the plane was
approaching a chain of mountains or a
city with tall buildings. Espenschied there-
fore proposed an electrical reflecting sys-
tem for use by airplanes using radio instead
of rail transmission. At that time, however,
1926, a really practical terrain clearance
indicator could not be built, largely be-
cause suitable radio instrumentalities were
not available. It was felt that vacuum tubes
capable of operating at frequencies some
fifty times higher than existing commercial
tubes could handle would be required be-
fore a satisfactory system could be built.

Although altitude determination was con-
sidered at various times following Espen-

schied’s first suggestion, it was not until
1930 that patents were applied for, and it
was not until June, 1936, that patents
2,045,071 and 2,045,072 were granted to
Espenschied for an airplane radio altim-
eter. Considerable commercial interest was
aroused, and in the following year a
group of Laboratories’ engineers headed
by R. C. Newhouse undertook to develop
commercial apparatus for Western Electric.

In 1938, a number of demonstration
flights were made, culminating on October
8 and 9, 1938, in a joint demonstration*
for the press by the Laboratories, the West-
ern Electric Company, and the United Air-

lines. During one of the early flights, it was
noticed that in addition to height above
ground, variations in the wave pattern on
an oscillograph gave indications of the
character of the reflecting surface beneath.
This suggested a still wider field of use,
and proposals were made that similar ap-
paratus, designed to project the beam
ahead, could be used to give warning of
approaching aircraft, mountains, or other
obstructions. Experiments of this nature
were carried out this same year in New
York harbor. In the avalanche of war de-
velopments that shortly followed, these and
other suggestions were used by the Lab-
oratories in their many radar projects.

To study microwave propagation through circular waveguides, it is necessary to begin with a
waveguide which is as nearly straight as possible. So Radio Research constructed this copper tube,
shown above, 1,200 feet in length, on supports which permit its accurate alignment. At the lower
left, A. P. King closes line short-circuiting switch which disconnects the line beyond the switch.
The other view shows R. Bown, H. T. Friis, M. J. Kelly and A. B. Clark inspecting line

In the years before the war, a number of
private-line teletypewriter systems had
grown to considerable size—some of them
spanning many states or even the entire
country. A case in point is the Republic
Steel Corporation. Its main office is at
Cleveland, where it also operates steel
mills, but it has other plants and offices ex-
tending from Boston to San Francisco and
from Buffalo and Detroit to Birmingham
and Houston. Since about 1925, these of-
fices and mills had been linked for teletype-

Fig. 1—The control panel for the private-line teletype-
writer network at the Cleveland office of the Republic
Steel Corporation

writer communication through a system of
private lines, which in more recent years
had been augmented by TWX service.”
Switching was all done manually, however.
A message from Chicago to New York, for
example, would first go to an operator in
Cleveland who would establish manually a
connection to New York. Twenty-six pri-

vate-line teletypewriter circuits were in
use, and traffic over these circuits was ex-
tended by TWX service to points all over
this country.

About 1940, it was felt that faster and
more economical service could be secured
by the use of automatic switching, and after
an extensive analysis by the Bell System,
the 81B1 teletypewriter private-line switch-
ing system was decided upon. The original
installation was completed in October,
1941, just in time to handle the rush of war
business. Besides greatly increasing the
speed of service, this new system made it

line teletypewriter circuits from twenty-six
to thirteen. Seven of these thirteen are con-
nected to the automatic system, and each
of the circuits serves a number of receiving
and sending stations.

In fundamental principles, this type of
automatic private-wire teletypewriter
switching differs basically from telephone
switching. With the latter, the complete
communication path between the originat-
ing and called stations must be idle before
a connection can be established and the
transmission of intelligence begun. When
the paths are not idle, repeated time-
absorbing attempts using expensive facili-
ties must be made to reach the called sta-
tion. In the teletypewriter system, however,
once a message has been perforated in a
tape and this tape placed in a transmitter,
no further action by the sender is required
for the transmission of the message. The
sender's transmitter sends the message to
the switching center as soon as the path to
the center is available. At the switching
center, facilities are provided to receive and
sort the messages and to store them until
the outgoing path to the called party is
free. In this manner, messages are carried
as far on their way to the ultimate receiver

as idle facilities permit before they are de-
layed to wait for a free path.

At the switching point, Cleveland for the
Republic Steel Corporation, a group of
crossbar switches* is provided that has in-
coming circuits connected to their horizon-

tals and outgoing circuits to their verticals,
so that any two circuits may be connected
together. Director and sequence circuits,
consisting chiefly of relays, control the op-
eration of the crossbar switches. Local tele-
typewriter transmitters and receivers are
associated with the crossbar switches to
handle messages originating or terminating
at the switching office and for certain su-
pervisory services, but the major unit of
the switching system is the 14-D reperfo-
rator transmitter, which will be described
in more detail in a subsequent article. In
brief, this unit consists of a combined typ-
ing reperforator and a transmitter. The for-
mer perforates a tape in accordance with
the received signals and at the same time
prints the message on the tape, while the
latter receives the tape punched by the re-
ceiver and retransmits the message, includ-
ing the last character punched. Between the
receiver and transmitter are facilities for
storing tape.

Incoming messages for passage through
the switching system arrive at one of these
machines, and a tape is punched as a mes-
sage comes in. The first two characters of
the message will be a code indicating the
ultimate destination, and the last two char-

acters indicate a disconnect. The transmit-
ter forwards this code to the control circuit
of the crossbar switches, pauses until it has
been notified that the connection has been
made, and then transmits the message. __

on the crossbar switches, and each vertical
is connected to the receiving side of a re-
perforator transmitter. If one of these is
receiving, a message from the incoming side
of the office will be connected to the other,
which will punch a tape and store it. This
makes that message available for transmis-
sion as soon as the outgoing line is free,
and permits the incoming line to send its
following messages to other outgoing lines
that may be ready to accept them, thus
speeding up trans-office transmission. Dur-
ing traffic peaks a back load of messages
may accumulate awaiting transmission, and
these will be sent out in approximately the
order in which they were received as the
outgoing line becomes available, thus keep-
ing the outgoing lines in use continuously.
Each_ reperforator transmitter and _ its
mounting arrangement can store about
seventy-five feet of tape, which corresponds
to about 1,500 words. Since the ordinary
messages and orders run from fifty to three
hundred words, ample storage is thus pro-
vided to carry the system over any ordi-
nary peaks of load.

Besides its reperforator transmitter, each
incoming circuit has a receiving teletype-
writer that can be connected to the circuit
in place of the reperforator transmitter

Fig. 3—Each cabinet houses two reperforator
transmitters with tape storage space in the
lower section

when the message is for the local office.
When the reperforator transmitter recog-
nizes by the code of a message that it is for
that office, it operates relays to disconnect
itself from the circuit and to connect in the
receiving teletypewriter.

The transmitters at the distant stations
are under control of the switching office,
which automatically starts those on any
given line in turn by start patterns of tele-
typewriter characters sent from the switch-
ing office. Arrangements are also provided
to start these transmitters by the manual
operation of keys at the switching office.

One of the fundamental principles of this
type of teletypewriter switching is that no
message shall be lost or delayed more than
a few minutes. Provisions are made, there-
fore, for taking care of such errors as incor-
rect or missing switching codes that other-

There are occasionally times when a par-
ticular plant or office, perhaps because of
holidays or other such circumstances, is not
able to receive messages. To take care of
such situations, keys at the control board
may be operated to permit messages to any
station on an outgoing circuit to be directed
to a willful intercept circuit. This includes
one or more reperforator transmitters which
will store all messages received until they
can be transmitted to their destination.
When this time comes, the messages are

The control panel from which the willful
intercept is controlled is the nerve center
for the entire system. It has lamps to indi-
cate what machines are sending, what cir-
cuits are busy or idle, and all the many
things that those responsible for the opera-
tion of the system should know. From here
also is controlled the order in which the
various stations on a single circuit are al-
lowed to transmit. The control panel for
the Cleveland office of Republic Steel is
shown in Figure 1.

A general view of the teletypewriter oper-
ating room in Cleveland is shown in Figure
2. In the left foreground are the receiving
teletypewriters that receive messages for
the Cleveland office. To the right of these
are machine cabinets containing the reper-
forator transmitters on the receiving cir-
cuits. As shown in Figure 3, each cabinet
has two reperforator transmitters with stor-
age spaces for their tapes. Next to the right
is the control panel and then the reperfora-
tor transmitters on the outgoing circuits.
In the cabinets at the rear are the crossbar
switches and the various relay control cir-
cuits. At the right are order writing and
originating machines where messages from

== PRIVATE TWO-WAY
PRIVATE ONE-WAY
BELL SYSTEM
® AUTOMATIC SWITCHING CENTER

Fig. 4—Republic Steel Corporation’s private-line teletypewriter network. It consists of six main duplex
circuits and a single circuit to Gadsden, Alabama

the Cleveland office are originated. The su-
pervisors desk where the intercepted mes-
sages are handled is at the rear of this
group just in front of the relay cabinets.
The complete teletypewriter network of
the Republic Steel Corporation is shown in
Figure 4. There are six main duplex circuits,

THE AUTHOR: W. M. Bacon, after graduating
with the E.E. degree from Cornell in 1930, joined
the D & R and was concerned with teletypewriter
development problems. This work was continued
with the Laboratories telegraph facilities group
after the 1934 consolidation, and has involved main-
tenance, repair, and installation methods and _ pro-
cedures as applied to teletypewriters. From 1938
to the present time, he has been engaged in the
development of private-wire teletypewriter systems,
including full automatic and manual switching sys-
tems. During the war years he was engaged in
developing teletypewriter cipher arrangements for
the Armed Forces.

each with a number of stations connected
to it and one single circuit to Gadsden, Ala.
At Cleveland, Chicago, New York, and
Gadsden, the network is associated with
the Bell System teletypewriter service, and
messages to offices not on their private-line
network are transmitted over the TWX.

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SAN FRANCISCO | INDIANAPOLIS MASSILLON
KANSAS CITY 4 PCINCINNATI
ST. LOUIS
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LOS ANGELES
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In the past fifteen years, the waveguide
has been developed from an electrical curi-
osity to an important medium for micro-
wave transmission. Progress was especially
rapid during the war years, since many of
the most important developments in radar
would have been virtually impossible with-
out waveguides. It is now possible to judge
with some perspective the rdle that wave-
guides will play in communications devel-
opments of the near future. Hollow-pipe
guides do not assume a thoroughly practical
form until the wavelength is shorter than
about thirty centimeters. At this upper
limit, the waveguide has supplanted coaxial
cable in some instances. For shorter wave-
lengths, it becomes increasingly attractive,
so that at ten centimeters it is the preferred
medium for the efficient, shielded transmis-
sion of wave power, and at three centi-
meters it is almost exclusively used.

Although the earliest work emphasized
waveguides as a form of transmission line
for radio waves, it was apparent from the
outset that waveguide structures would be
required also to serve as numerous basic
electrical components. At low frequencies,
these components include such elements as
coils, capacitors, resistors, transformers, re-
lays, and switches. It was soon found that
waveguide counterparts of these low-fre-
quency elements could be constructed to
operate in the microwave region. To the
uninitiated, the electrical behavior and
physical form of these new components ap-
pear novel and even revolutionary.

The investigation of waveguide transmis-
sion and of related circuit elements, as car-
ried on by Dr. G. C. Southworth and his
associates, opened up vistas of a radically
new communications art for the Bell Sys-
tem. Expanding effort in microwave re-
search and development is now bringing

about a reduction to practice. The engineer-
ing of waveguide components, for example,
is already sufficiently far advanced to per-
mit construction of a microwave circuit be-
tween New York and Boston in a manner
only dreamed of ten years ago.

One ot the waveguide components which
is finding a wide variety of uses is the four-
arm junction shown in Figures 1 and 2. If
wave power is sent into this junction from
the arM s, Figure 2, half of the power flows
into each of the ARM 1 and ARM 2, with no
power appearing in the arm p. Conversely,
if waves are sent into the junction from the
ARM P, the power is again equally divided
between ARM 1 and ARM 2, with none flow-
ing into the aRM s. Thus, ARM s and ARM P
are balanced with respect to each other, pro-
vided ARM 1 and ARM 2 are terminated in
a symmetrical manner. Since the junction
provides balance reminiscent of the familiar
hybrid coil, it is called a hybrid junction.*

*The term “Magic Tee,” which has also been
applied to this construction, is felt to be a misnomer.

junction by itself. An important refinement
is realized, however, when reactive tuning,
as exemplified by the metal post and rod in
Figure 2, is associated with the junction.
These added elements improve the imped-
ance match of the junction to each of the
four arms, and thereby automatically bring
about a high degree of balance between
ARM | and ARM 2.

A qualitative explanation of the hybrid
junction can be arranged to bring out some
of the more important aspects of modern
waveguide theory and practice. It will be
recalled* that radio waves can be freely
propagated within any conducting tube, so
long as the wavelength is shorter than a
cutoff wavelength determined by the cross-
sectional size and shape of the pipe. There
is, indeed, an infinitude of transmission
modes, corresponding to different patterns
of lines of force, which can be established
and maintained for wave transmission, and
thus an infinitude of different cutoff wave-
lengths. For reasons of simplicity, however,
waveguide developments have so far been
confined almost exclusively to the mode of
longest cutoff wavelength, the so-called
dominant wave, in pipes so proportioned
that no other mode can be freely sustained.
Also, for practical reasons, only circular and
rectangular shapes are in common use. In
Figure 3, lines of electric intensity in the
dominant wave are shown for tubes of cir-
cular, square, and oblong cross-section. A
close resemblance to radio waves in free
space is evident.

There is an important difference between
symmetrical and nonsymmetrical pipes,
however, with respect to the permissible
orientation of the plane of polarization.
Patterns are shown in Figure 3 for both
vertical and horizontal polarization. In the
circular and square pipes, the configuration
may have any orientation, depending upon
the manner in which the waves were ini-
tially launched. In an oblong pipe, however,
the cutoff wavelength corresponding to the
cross-polarized oscillation can be depressed
below the operating wavelength, and only
the fixed orientation shown can be freely
transmitted.

An oblong shape is thus preferred when-
ever there is any chance that the polariza-

ARM P
Fig. 2—Perspective cut-away view of waveguide hybrid
showing “rod” and “post” used in impedance matching

Fig. 3—Electric field configuration in circular, square,
and oblong guides

METAL ROD
Fig. 4—A “post” at the upper left is equivalent to a
shunt capacitor, while a “rod,” lower left, is equivalent
to a shunt coil

tion may be rotated in an uncontrolled
fashion. Experience has shown that un-
avoidable irregularities or deliberate distor-
tions, such as bends, do tend to rotate the
plane of polarization in circular waveguides
to such an extent as to interfere seriously
with the normal operation of the system.
For the most part, therefore, waveguide
components have been developed with rec-
tangular guide. Best results are generally
obtained when the proportions of the cross-
section lie in the vicinity of 1 by 2, with
the larger inside dimension equal to about
three-quarters of a wavelength.
Waveguide studies are greatly facilitated
by the close analogies that can be estab-
lished with conventional transmission line
circuits. Just as the waveguide itself is rep-
resentable as a transmission line, so also can
waveguide components be replaced for
analytical purposes by equivalent networks
of impedance elements in association with
sections of line. For the simpler waveguide
structures, the equivalent networks are ob-
vious upon inspection or can be readily
derived from elementary consideration of
electric fields and currents within the con-
figuration. This is true, for instance, of the
post and rod already shown in the hybrid
junction. As indicated in Figure 4, the metal
post concentrates the electric field between
itself and the nearby wall of the guide, and
is equivalent to a capacitance placed in
shunt across a transmission line. With the

metal rod, on the other hand, the principal
effect is to provide paths for conductive
current flow between the connected walls
of the guide, with a resulting increase in
magnetic flux and flux linkages, and thus it
is like an inductance in shunt across a line.
Provided that reasonably good conductors
have been selected for the post and rod,
their resistance components can be neg-
lected except in extreme cases.

For more complex waveguide structures,
accurate representation in terms of equiva-
lent networks can often be reached only
after considerable study. This is true of the
hybrid junction. For a first approach to this
subject, equivalent network analysis is not
well suited. Instead, use can be made of

analogies with optics. Here the principal
concern is with the spreading of a wave
front from one portion of the structure to
the others. In a straight section of guide,
the wave fronts are plane; distribution of
the electric field has been indicated in Fig-
ure 3. In the vicinity of a severe discontinu-
ity such as an abrupt junction, there is local
distortion, wave fronts become curved, and
the field may follow a complicated distribu-
tion. An accurate knowledge of this distor-
tion is not essential, however, in deriving
important properties of the hybrid junction.

wave front spreads into a hybrid junction
from the ARM s. Lines of electric intensity
are drawn in several successive positions of
the wave front. To show why no power
flows into the ARM P, the electric intensity
in a typical position of the front is indi-
cated vectorially at two points a and B sym-
metrically disposed with respect to the cen-
ter of the junction. At a, the local field has
components a’ toward the left and a” down-
ward, while at B the components are b’ to-
ward the left and b” upward. From sym-
metry, the magnitudes of the respective
components at A and B are equal. Thus, the
downward and upward intensities a” and b”
cancel, or, more precisely, they induce
equal and opposite voltages in the ARM P

as the wave front spreads into that arm.
The intensities a’ and b’ reinforce each
other and tend to produce in the ARM P a
cross-polarized wave. If the aRM P guide is
correctly proportioned, however, the cross-
polarized wave cannot be freely propa-
gated. This shows that no power flows into
the aRM P as a result of the electromotive
force exerted at a and Bs. All other points
in the wave front can be grouped in pairs,
symmetrically located with respect to the
junction center, and the same conclusion
holds for each pair of points. From the

wave front as a whole, therefore, no power
flows into the arm Pp, and the power which
is transmitted through the junction must
appear in ARM I and ARM 2, and from sym-
metry, in equal amounts. It will be noticed
that at points equidistant from the junction,
the polarities of the electric intensity are
reversed in ARM 1 and ARM 2. With respect
to phase, at least, the ARM s acts as a trans-
mission line connected in series with the
line corresponding to ARM 1 and ARM 2.
What happens when a wave front spreads
into the junction from the ARM P is shown
in Figure 6. With respect to flow toward
the arm §, the lines of electric intensity are
seen to be directed so as to create only a
cross-polarized wave in the arm s. As in

the previous case, there are, in planes off-
center from the junction, additional com-
ponents arising from the curvature of the
lines of force, but these are cancelled by
the mirror image components on the other
side of the junction center. With properly
proportioned guide for the ARM s, there-
fore, no power flows into it from the aRM P.
This conclusion is in harmony with the reci-
procity theorem for electrical networks; if
no power can be transmitted from ARM s
and received at ARM P, then no power can
flow the other way when the positions of

Fig. 8—A balanced converter for the micro-
wave system between New York and Boston

Figure 6 also indicates how power from
the ARM P spreads into ARM 1 and ARM 2.
With complete symmetry prevailing in
these arms and their terminations, the
power is equally divided between them.
Here the geometry does not act to reverse
the polarity of lines of force, and at equal
distances from the junction, voltages in
ARM 1 and ARM 2 are in phase. From this
consideration, the ARM P is regarded as
analogous to a transmission line connected
in parallel across a line corresponding to
ARM I and ARM 2.

To reveal clearly the balancing and
power dividing properties of the hybrid
junction, the picturization of wave propa-
gation has been simplified by neglecting
waves reflected from various parts of the
junction. On account of the sharp geometri-
cal discontinuities involved, field patterns
in the region of the junction are in reality
very complicated, corresponding to the
superposition of waves bouncing back and
forth within this region. All reflected com-
ponents are symmetrical or paired with re-
spect to the center, so that they are inca-
pable of disturbing the balance or power
division. The presence of reflections does,
however, lead to a serious impedance mis-
match of the device to the individual arms.
These mismatches can be eliminated by in-
corporating within the junction tuning ele-

ments, such as the rod and post visible in
Figure 2. From an optical point of view,
they are regarded as sources of additional
reflections whose amplitudes and phases
are such as to bring about cancellation of
the original reflections. In terms of network
analysis, the rod and post are equivalent,
as has been pointed out, to a coil and ca-
pacitor, and are disposed so as to tune out
the reactance associated with the equivalent
network of the junction. By a proper choice
of tuning elements, effective neutralization
of reflections can be obtained over a re-
markably broad band of frequencies. Other
tuning means, metal plates for example, can
be used in place of the rod and post. The
particular combination shown, developed
by C. F. Edwards, is being widely used.

When the hybrid junction has been
matched by reactive tuning, it exhibits the
further customary property, that of balance
between ARM 1 and ARM 2. If power is
caused to flow into the junction from ARM 1,
a hasty analysis of wave-front propagation
leads to the conclusion that the power will
be divided in some fashion among the other
three arms. This is indeed true. The use of
matching reactors, however, automatically
brings about a balance between arm 1 and
ARM 2, so that power flows only into the
ARM Ss and ARM P and is, moreover, evenly
divided between them. This behavior, while
not obvious from an optical standpoint, is
a necessary consequence of the law of reci-
procity.

Hybrid junctions have been built from
various sizes of guide for use at frequencies
in the vicinity of 4,000, 6,000, 9,000, and
24,000 megacycles per second. Constructed
with reasonable care, they provide an isola-
tion of 35 to 40 decibels between the ARM s
and ARM P, and satisfactory impedance
matching over frequency bands as wide as
twelve per cent. If unusual pains are taken
to secure a geometrically symmetrical junc-
tion, the balance is improved to 50 decibels
or more.

The hybrid junction can be used in the
same way as its low frequency counter-
part, the hybrid coil. The junction has, in
addition, many diverse applications in
microwave systems and in laboratory meas-
urements, so that it already occupies as
important a position in centimeter wave

techniques as does the hybrid coil in low-
frequency practice. New uses are constantly
being discovered in which advantage is
taken of the balance, power division, and
phasing afforded by the junction.

Perhaps the most important use so far
found for hybrid junctions is in the bal-
anced converter. Since this was also one of
the earliest applications, it has been
brought to an advanced stage of develop-
ment. The general principles underlying the
operation of the balanced converter or first
detector are shown in the block diagram of
Figure 7. Two detectors, in this case point-
contact silicon rectifiers, are used as termi-
nations for ARM 1 and ARM 2 of a hybrid
junction. The beating oscillator power is
introduced from the arm s, and the signal
input from the arm p. With this arrange-
ment, half of the signal power and half of
the beat frequency power are developed in
each rectifier. The 180-degree phase shift
between the signals in ARM 1 and ARM 2 by
the nature of the series connection persists
in the intermediate-frequency voltages de-
veloped at the two rectifiers. By combining

the two intermediate-frequency signals with
proper phasing, however, all of the inter-
mediate-frequency power can be made
available in a single output.

An important advantage afforded by such
a balanced detector is the isolation achieved
between the signal line and the local beat-
ing oscillator. If care is taken to build a
truly symmetrical structure and to use rec-
tifiers which are as nearly identical as pos-
sible, this uncoupling corresponds to the
balance between the ARM s and ARM P of
the hybrid junction. Another advantage is
that the same intermediate-frequency phas-
ing which combines the two intermediate-
frequency signals additively causes noise
contributions from the beating oscillator to
be cancelled. For these and other reasons,
the balanced converter is considered the
most efficient and desirable microwave de-
tector now available. A specific construction
developed by C. F. Edwards is illustrated
in Figure 8. This is the converter that is
now being used in the microwave repeater
system between New York and Boston, de-
scribed in the last issue of the Recorp.

THE AUTHOR: Warren A. Tyrrett received a
B.S. degree from Yale in 1935 and a Ph.D. degree
in Physics in 1939. Upon graduation he joined the
Technical Staff of the Laboratories and was as-
signed to the waveguide research group. During
the war he developed a number of components for
use in Navy radar systems. Since the war, Dr.
Tyrrell has continued his work on waveguides at
the Holmdel Laboratory in New Jersey, and is
engaged in the application of waveguide tech-
niques to measurements on dielectric and metallic
material.

An ideal hearing aid would have the
highest acoustic performance that the ear
could appreciate and be small in size and
weight. These two major objectives, how-
ever, tend to oppose each other; the highest
performance, including high gain and
power output, tends to require more appa-
ratus and thus larger size and weight. Since
the Laboratories has always considered that
high quality was the primary factor, West-

ern Electric hearing aids have led the field
in performance ever since the first 220-
pound set of 1923. Size and weight reduc-
tions have come steadily, but they have
depended on the development of materials
and techniques that would permit the two
objectives to be more effectively reconciled.
Advances since the war greatly helped in
this direction, and following the 64-type
hearing aid. which came out immediately

after the war, the Laboratories has devel-
oped the Models 65 and 66 hearing aids.
These achieved greater convenience and a
much smaller weight than previous designs
—six and eight ounces, respectively, includ-
ing batteries—and the 66 equals the high
performance of the best previous aids.

In attaining excellent performance with
very small size and weight, dependability
in service has not been sacrificed. The com-
ponents selected for the sets meet require-
ments of stability and ruggedness that
assure they will stand up under conditions
of use. In addition, many special measures
have been taken to protect the components
against the adverse effects that are en-
countered with moisture and dirt.

One of the innovations of the new devel-
opment is the provision of two sets rather
than a single set. In designing previous
sets for the highest practical quality, the
Laboratories has recognized that the user
with only a small hearing loss was wearing
an aid that had much more gain and range
than he needed. The provision of two sets
meets this situation, since one of them is
designed to provide the best possible hear-
ing for anyone with a correctable hearing
loss, while the other, smaller and with less
gain and power capacity, will satisfactorily
serve the great majority of those requiring
a hearing aid.

These two new sets are shown in Figure
1. Each consists of a plastic case housing
the transmitter, amplifier, battery, and con-
trols, to which a No. 724-type midget re-
ceiver and cord is attached. The Model 66
case is in either two tones of grav or flesh
color, while the Model 65 is either dark
gray or flesh. The microphones for both
sets are of the crvstal tvpe, and each bas a
three-stage vacuum-tube amplifier with a
volume control and also a tone control that

may be used to suppress the lower frequen-
cies of background noise. The amplifier
circuit for the Model 66 set is shown in
Figure 2. The amplifier for the Model 65
has no feedback, and some of the capaci-

This protected network principle is ap-
plied throughout the set. For the Model 66,
all circuit elements between the first and
second vacuum tubes are assembled in a
compact, self-supporting group molded in

A cross-section of the crystal microphone
is shown in Figure 3. It is sealed by a
plastic-coated metal-foil membrane across
its face, and by closing other potential
points of moisture leakage with moisture-
proof plastic cement. Microphones for both
sets are of essentially the same construction,
but that for the Model 65 is somewhat
smaller than that for the Model 66. The
capacitor and resistors of the tone control
network are housed in the microphone case.
This not only protects these high-imped-
ance elements from moisture but also
shields them electrically.

a block of wax to form a moistureproof and
tamper-proof network. Interconnections are
made by wires that are parts of the ele-
ments, thereby reducing the number of
joints required. Many of the connections are
welded instead of soldered. The circuit ele-
ments between the second and third stages
are treated in a like manner.

In the Model 65 set, this principle is ex-
tended. The entire amplifier—vacuum tubes,
capacitors, and resistors—is wired together
by the element’s own leads, and is then
molded in wax to protect it from dirt and
moisture. The resultant package is 1% by
1% by % inches. In case of failure of any of:

the elements, the entire network is replaced.
The complete chassis for the Models 65 and
66 sets are shown in Figures 4 and 5.

One of the distinguishing features of both
sets is the absence of distortion and a mini-
mum of noise due to clothing. If adequate
precautions are not taken, the noise of
clothing rubbing against the set, which
reaches the microphone either as mechan-
ical vibration or as airborne sound, may so
mask the useful sounds that the value of
the hearing aid is seriously impaired. In the
new hearing aids, it has been reduced at
its source by the avoidance of any sharp
corners or projections on the case, and by
making the case of a material that has a
very low coefficient of friction. In addition,

the microphone is protected by a resilient
mounting against any mechanical vibration
that may be generated.

Besides providing two sets—one for those
needing considerable aid and the other for
those requiring only a moderate amount—a
further division of the range is provided by
additional options in the size of the battery
(in the Model 66) and the type of the re-
ceiver used. There are three 724-type
receivers, the A, B, and C. Their character-
istics are shown in Figure 6. The 724C has
a flat characteristic extending from below
200 to over 4,000 cycles. The 724B gives
greater output, but its response falls off
above 3,000 cycles. The 724A has the same
frequency range as the 724B, but has a high
output peak at about 1,200 cycles which is
helpful in some extreme cases. Only the
724B and 724A receivers are applicable to

the Model 65 set, but all three may be used
with the Model 66, as may also the 725
bone-conduction receiver.

of increasing the sound intensity reaching
the ear by 55 db and of producing a sound
pressure in the ear of 116 db above the
minimum pressure that can be heard by a
normal ear. The frequency range under
these conditions is from 250 to 4,000 cycles.
Within this range, the response is uniform
within +6 db. This flat response may be
changed to one that rises toward the high
frequencies at either 5 or 10 db per octave
by turning a three-position tone control
switch. Another control permits adjustment
of amplifier gain over a 40 db range.

A special feature of the design of the
Model 66 set is that the battery compart-
ment may be detached and replaced by a
small adaptor from which a cord extends to
an external battery case. This permits the
use of higher voltage, or of larger, more
economical batteries, when desired. By tak-
ing advantage of this feature, amplification
and sound pressure may be increased 4 db
by using a 30-volt external B battery. These
characteristics may also be increased 7 db
by substituting the high-efficiency 724B
receiver for the 724C. This latter method
entails some sacrifice of high-frequency re-
sponse. In extreme cases, both of these sub-
stitutions may be made with a resultant
amplification of 66 db, and the maximum
sound pressure level of 129 db. This pres-
sure is about the maximum that the ear can
tolerate.

With the Model 65 aid, a 15-volt B bat-
tery is employed, and when using a 724B-
type receiver, which is recommended in
most cases, the acoustic amplification is 50
db and the maximum sound pressure in the
ear is 115 db above normal threshold. The
effective frequency range is from 700 to
3,200 cycles, but even at 300 cycles, the
response more than meets the requirements
of the American Medical Association. With-
in the effective range, the response is nor-
mally quite flat, but may be tilted to slope
upward toward the high frequencies at
either 4 or 8 db per octave. Somewhat dif-
ferent gain and frequency characteristic is

possible by using the 724A receivers. Over-
all characteristics for the most commonly
used combinations of the two sets are
shown in Figure 7.

These two hearing aids thus complement
each other. The Model 66 has the superior
acoustic performance that is required by
those who have a severe hearing loss or
who want exceptionally good acoustic qual-
ity. On the other hand, the Model 65 is

THE AUTHOR: J. R. Power received a B.S. de-
gree in Electrical Engineering from Carnegie Insti-
tute of Technology in 1927. Entering the Appara-
tus Development Department of the Laboratories
that same year, he engaged in the development of
special motors and generators for use primarily in
sound pictures. In 1935 he transferred to work on
acoustical problems connected with noise condi-
tions in the telephone plant and offices. Later he
spent some time on the preliminary development
of a new telephone ringer. This was interrupted by
work on high power auditory systems for the Gov-
ernment. Since the end of the war, he has been
engaged in the development of hearing aids,
audiometers, and artificial larynges.

Fig. 7—Gain-frequency characteristics of various ar-
rangements of the Models 65 and 66 hearing aids

smaller and therefore more convenient to
wear. The reduced size causes no loss in
dependability. Its acoustic characteristics
are of good quality and are entirely ade-
quate for the majority of hard-of-hearing
people. By offering the choice of either of
these two sets, Western Electric is carry-
ing out its long-established policy of ren-
dering the greatest possible assistance to
any person who is hard of hearing.

“Congresso Internazionale per il Cinquan-
tenario della Scoperta Marconiana della Radic,”
was the announcement spelled out by ban-
ners stretched across the streets of Rome as
engineers and physicists from many countries

name of Guglielmo Marconi. The tenth anni-
versary of Marconi’s death was the fiftieth an-
niversary of the pioneering experiments of this
brilliant and energetic Italian in wireless
communication.

Sponsoring the Congress was the National
Council of Research, whose fine headquarters
building near the University of Rome was
the scene of the technical sessions. My assign-
ment was to represent the Laboratories and
to give a paper dealing with our contributions
to the design of modern broadcast transmitters.

Mouromtseft of Westinghouse, Zworykin of
RCA, and Bolt of MIT were other Americans
participating as the Congress commenced on
a Sunday afternoon with ceremonies in the
Campidoglio, or state capitol. Among the many
foreign scientists I met for the first time were
Smith-Rose from England and Strutt from
Holland, whose names are familiar to all ra-
dio people through their many publications.

The papers presented during four days of
technical sessions covered a wide field, includ-
ing acoustics, wave propagation, circuit theory,
vacuum tubes, communication systems, aural
broadcasting, and television. Numerous Italian
papers testified to a lively scientific endeavor
in that country despite the present difficult
economic conditions; while the importance as-
sumed by microwave papers was in line with
the technical trends of the times. Indeed,
Marconi himself had been an enthusiast over
centimeter waves, and no one a generation
ago envisioned more clearly than he the vast
possibilities for their practical use.

ments Rome has to offer, the delegates wel-
comed a program arrangement that left time
for sightseeing, though in a visit of ten days
one could only glimpse briefly the “high spots”
of the Eternal City. The management of the
Congress arranged for splendid side trips to
Villa d’Este at Tivoli, with its beautiful foun-
tains and gardens; to the picturesque ruins
of Ostia, ancient Roman port at the mouth of
the Tiber; and to Castelgandolfo, papal sum-
mer residence, for an address by Pius XII
and a personal introduction to the pontiff for
each member. An evening concert provided
by the Italian broadcasting organization and
an inspection tour of the international radio
transmitting station of Italeable at Torrenova
rounded out a busy week. The Torrenova
plant, a great communications center almost
completely destroyed by the Germans, is be-
ing rebuilt and equipped with the most mod-
ern long-wave and short-wave radio telephone
and telegraph equipment for European and
overseas transmission.

After the close of the Congress on October
5, I spent a month visiting industrial and
university laboratories and radio stations in
Switzerland, France, Holland, Belgium, Lux-
embourg, England, and Ireland. An outstand-
ing affair I attended in London, attracting the
general public from all over England, is Ra-
diolympia. Resumed this year, after a lapse
of eight years, this exhibition of radio products
of all kinds drew half a million spectators in
ten days, a remarkable show of interest for
these hard times. Improvements in radio tech-
nique, stemming from the intensive war ef-
fort in England and America in electronics,
are plainly seen in these products; and _ all

The photograph at the head of the page shows
the author (right) and V. I. Enders of Alpine
Western Electric, Switzerland, returning from a
sail on the Lake of Zurich.

To review the progress of development and
manufacturing of wire, cables and cords, a
conference of engineers and executives of the
Laboratories and the Western Electric Com-
pany was held at the Point Breeze Works in
October. This was the first in a series of similar
conferences to discuss joint development and
manufacturing problems. The second was held
at the Kearny Works on December 10 and 11
and dealt with the development and manu-
facturing of transmission apparatus.

Under the general direction of M. J. Kelly,
the Kearny conference was planned by R. G.
McCurdy, H. H. Lowry and H. Rossbacher,
Works Engineer of Manufacture at Kearny.
After an introduction by R. F. Clifford, Works
Manager, the program was outlined by Dr.
Kelly and H. C. Beal, Vice-President of the
Western Electric Company.

Presentations were made by engineers of
the Laboratories and of Western Electric cov-

ering a number of areas of development and
bringing out the relationships between the
manufacturing and development problems in
these fields. The subjects covered included
coaxial line and terminal equipment, televi-
sion terminals and video amplifiers, networks,
equalizers and filters, measurement problems,
crystals, component apparatus, the current
size-reduction activities, and transmission
economics.

It is the purpose of these conferences to
bring up for discussion at an early date prob-
lems of engineering design and problems of
manufacture relating to the developments be-
ing made by the Laboratories. As a result of
these discussions, the manufacturing and de-
velopment programs are geared together to
achieve maximum effectiveness in translating
new ideas from the Laboratories into equip-
ment for the operating telephone companies
of the Bell System.

over Europe, despite severe shortages in
materials and components, one finds great
activity in the development of new com-
munication equipment operating in the ultra-
high-frequency and microwave bands and
employing FM and pulse modulation multi-
plex methods.

Television is popular in Britain, and video
transmitting stations are planned for Birming-
ham and other important centers. For linkage
with the present London installation, trials of
both radio relay and broad-band coaxial cable
are to be made, somewhat paralleling our own
television network plans. British receivers, in-
terestingly enough, differ from ours in being
built for one channel only and for carrier-
and-double-sideband reception.

The diary of the American traveler in Eu-
rope is sure to contain references to the droves
of bicycles on the streets of Dutch and Swiss
cities; to the immense variety of noisy motor-
bikes and midget cars that dart about dan-
gerously in Rome and Paris; to food ration-
ing and London fogs. My notes mention these
and other experiences, but the really deep
impressions were of warm hospitality extended
by Europeans everywhere, and of diligent and
courageous efforts toward recovery in coun-
tries hard hit by the war.

Political tension was evident in Italy and
France, with daily threats of a general strike,
but except for a short walkout on the metro
in Paris, there was no outward disturbance.

The subsequent outbreaks of violence make
one glad to be safely back, but concerned for
the new friends left on the Continent to
weather the storm.

In a move to further accelerate the Bell
System’s nation-wide construction program, the
Laboratories has developed a new type of
telephone cable sheath using a thin sheet of
aluminum covered with a polyethylene com-
pound, a tough, flexible plastic that looks like
black rubber. The new cable will supplement
the familiar lead-covered cable which is now

at peak production. Following extensive tests
of its suitability, the Western Electric Com-
pany has begun quantity production of the
new type of cable at Kearny and Hawthorne.
The cable, called “Alpeth,” is to be used
within local exchange areas on pole lines and
in underground conduit. It will be made in a

variety of sizes, ranging from the smaller ca-
bles to those containing hundreds of pairs
of wires.

The immediate purpose to be served by
the new cable will be to step up the deliv-
ery of cable to the telephone companies and
help meet the continuing heavy demand for
telephone service.

The name “Alpeth” is derived from the
sheet of aluminum which goes next to the
paper-insulated wires, and from the outer
covering of polyethylene. Before carbon black
is added, the polyethylene has a milky color.

For many years the Laboratories has car-
ried on continuous research on cable improve-
ment. Insofar as can be predicted from lab-
oratory and field tests, polyethylene promises
to give satisfactory service as a cable sheath
material. No change has been made in the
cable core itself.

Meanwhile, with the production of lead-
covered cable continuing at a record pace, the
new composite sheathing is helping to increase
still further the total output of much-needed
exchange cable.

Eprror’s Nore: A more extensive account
of this development will appear in an early
issue of the REcorp.

Philatelists exhibited their prize specimens
at an exhibition in the Lounge at Murray
Hill on November 20 and 21, signalizing the
beginning of the newly organized Stamp Club
at that location under the direction of the
Bell Laboratories Club. S. C. Tallman was
awarded first prizes for his displays in both
the United States and foreign classes. C. W.
Ferguson and K. H. Schunke took second
prizes in those classes, while H. T. Webber
took both prizes in the novelty class and also
won the award “best in show.”

W. A. Shewhart sailed for Southampton on
November 22 on the first leg of a trip by boat
and plane to India for a four months’ visit
and lecture tour. Dr. Shewhart’s invitation
was sponsored jointly by the Indian Standards
Institution; the Indian Science Congress As-
sociation, the Indian counterpart of the Ameri-
can Association for the Advancement of
Science; and the Indian Statistical Institute,
the largest research organization of its kind
in the world. As Visiting Professor to the Sta-
tistical Institute, he plans to give a series of
lectures at Calcutta University and one or
more lectures elsewhere in India. He will also
participate in round-table quality control

conferences in Bombay and Calcutta with stat-
isticians, industrial leaders and technical rep-
resentatives from all over India.

In his lecture equipment, Dr. Shewhart in-
cluded pamphlets describing the over-all or-
ganization and workings of the Bell System;
descriptive material and lantern slides showing
views of the newer Laboratories’ buildings -
and equipments; a Fastax camera; and a
colored sound film on quality control.

The Murray Hill Chorus presented a varied
program of Christmas music in the Arnold
Auditorium on Tuesday, December 23, with
the audience participating in several of the
familiar carols. Daniel F. Kautzman directed
the Chorus and Capitola Dickerson was the

M. J. Kelly receives the Presidential Certificate of
Merit from Secretary of the Navy John L. Sullivan
“in recognition of his efforts in the field of elec-
tronics which proved to be an invaluable contribu-
tion to the war effort of the United States.” The
presentation ceremonies were held in Washington
on November 19

accompanist. W. H. Martin, chairman of the
Murray Hill Committee, gave the annual
Christmas greeting.

Carols were sung outdoors at Whippany,
where members of the Laboratories gathered
on the steps of the Administration building at
noon on Christmas Eve. At about the same
time, the System’s Christmas Chorus of sixty-
seven voices rendered a selection of carols in
the drafting room of the Equipment Develop-
ment Department on the ninth floor at West
Street. The carolling was picked up by a
microphone, transmitted into the courtyard,
and amplified, so that many more members

Present at a conference to
appraise technical and re-
lated subjects submitted to
the Patent Department for
consideration are, standing
(left to right), Loretta
Spacek, Catherine Mc-
Queeny, H. A. Burgess, G.
H. Heydt, R. E. Poole, N.
S. Ewing and E. L. Nelson.
Seated around the confer-
ence table are (left to
right) E. V. Griggs, J. W.
Schmied, H. A. Blake, M.
R. McKenney, D. A.
Quarles, W. C. Kiesel and
J. R. Wilson

of the Laboratories than could be accommo-
dated in the Auditorium had the pleasure of
hearing the program. Under the direction of
R. P. Yeaton, the chorus sings together only
at Christmas and has been in existence five
years. Originally comprised of draftsmen, it
has grown each year, adding, as it did in 1947,
a number of trained new voices from other
departments.

Many inquiries have been received regard-
ing the New York State veterans’ bonus in con-
nection with transfers to New Jersey or other
out-of-state locations of the Laboratories and
subsequent changes in residence. To be eli-
gible, the bonus law states “residence in New
York State at the time of entry into service
and at least six months immediately prior, and
residence in the state at the time application
for bonus is made out” is necessary. Thus, a
member of the Laboratories who has been a
resident of New York State is not eligible for

the bonus if he or she changes his or her
residence to another state before application
for the bonus is made. Some veterans may be
required to file special residence question-
naire forms after submitting their applications
in order to clarify their domicile status.

New York State veterans who are on leaves
of absence from the Laboratories to attend
school are eligible for the bonus unless there
are indications that he or she has become a
permanent resident of some other state.

H. A. Blake, Assistant Commercial Relations
Manager, was transferred to the Patent De-
partment on October 22 as Executive Assistant
to M. R. McKenney, General Patent Attorney.

Coincident with this appointment, C. R.
McConnell and H. Schmitt, Commercial Proj-
ects Supervisors for New York and Murray
Hill, respectively, now report to B. B. Webb.
The title, Assistant Commercial Relations
Manager, has been discontinued.

During the Months of September, October and November the United States Patent Office
Issued Patents on Application Filed by the Following Members of the Laboratories

T. Aamodt R. C. Davis R. H. Gumley F. B. Llewellyn R. K. Potter
W. P. Albert (2) T. L. Dimond H. A. Hilsinger, Jr. G. A. Locke R. M. Ryder
M. C. Biskeborn R. A. Ehrhardt W.H.T. Holden (2) G.R. Lum J. H. Scaff

F. B. Blake C. H. Elmendorf H. Hovland W. P. Mason (2) ©. A. Shann
E. M. Boardman E. P. Felch, Jr. R. G. ——* A. L. Matte F. J. Singer

J. H. Bollman (2) ~~ A. G. Fox E. M. Julic W. H. Matthies T. Slonczewski (2)
W. L. Bond A. L. Fox A. P. King H.J.McSkimin J. Tarr

A. E. Bowen (2) C. J. Frosch W. Koenig, Jr W. J. Means H S. Wertz
D. E. Branson G. W. Gilman J. A. Krecek W. A. Mehmel H Whi '
H. W. Bryant H. W. Goff J. G. Kreer, Jr. E. A. Nesbitt A. H. White
A. J. Busch W. M. Goodall A. G. Laird C. W. Norwood H. T. Wilhelm
J. A. Carr H. L. B. Gould A. G. Lang W. G. Pfann R. O. Wise

B—Graybar’s committee, Rose Rovegno, Molly
Radtke, chairman; Eve Coll, Mary Burke,
Shirley Zitzmann, and Marion Greenberger

C—Whippany’s committee. In the rear, Dor-
othy Clothier, Harriet Filmer, chairman;
Joan Helm, Evelyn Selzer, and “Pat”
Rooney; center, Bette Mocksfield, left, and
Marion Merck, right; front row, Marilyn
Miller, Betty Minerowitz, Elizabeth Myers,
and Jean Force

D—F. D. Leamer, president, and Mrs. Anne
Brokaw, executive secretary, Family Serv-
ice Association of Summit, accept toys from
Dorothy Thom

E—Peggy Grillo and three children of the
Nursery School at the Greenwich House

G—Dennis Cronin admiring the little dogs he
made from wash cloths for the display

H—Madeline Kiselica exhibiting story book
and opera character dolls she dressed

J—At Whippany, Mrs. Filmer (left) with
guardians of children in boarding homes

K—Mary Mahairas(left)and Florence McGuire
present gifts to servicemen’s children at a
party given by the Red Cross in Flushing

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Progress on Project No. 2 at Murray Hill indicates that the first of its new occupants can begin to
move about August 1 of this year. The chart on the opposite page shows where you will find the
various departments when the moves are completed some time in 1949. The shaded arrow (circle,
upper right) indicates the direction usually referred to as “North”

M. J. Ketiy addressed the engineering and
supervisory force of the Southwestern Bell
Telephone Company at St. Louis. He also at-
tended the biannual meeting at Rolla, Mis-
souri, of the Board of Directors of the Missouri
School of Mines Alumni Association on No-
vember 7. On the following day, Dr. Kelly de-
livered the main address at the Homecoming
Convocation at the School, his alma mater
(B.S., 1914, and Honorary Doctorate in Engi-
neering, 1936), selecting as his subject Science,
Technology and the “Good Society.”

Durinc a two-day Research Conference in
Washington of the Navy Industrial Association,
Dr. Kelly, who is Chairman of the Research
and Development Committee, addressed the
Conference on its opening day, November 18,
at a dinner session. His subject was Our Coun-
try’s Preparedness Research and Development
Program—A Codéperative Undertaking of Our
Military, University and Industrial Laboratories.

D. A. QuaRLEs went to Chicago for the Board
of Directors meeting of the American Institute
of Electrical Engineers. He was also in Wash-
ington on November 13 attending the meeting
of the Committee on Electronics of the Joint
Research Board and on November 19 attend-
ing the Navy Research Conference of the Navy
Industrial Association.

A. B. CLARK was a guest at the Navy Confer-
ence in Washington on November 18 and 19.

On November 25, Mr. Clark, H. H. Lowry,
F, J. Scupper, T. C. Fry, J. G. Fercuson and
F. A. Korn conferred with officials of The
Bell Telephone Company of Pennsylvania in
Philadelphia, and visited the No. 5 crossbar of-
fice in Media.

HARVEY FLETCHER has written on The Science
of Hearing in the book The Scientists Speak.
Two retired members of the Laboratories have
also contributed articles to the book, H. E.
Ives, Physics and Art, and R. R. WiLiiaMs
with R. J. Williams, The Golden Age of Bio-
chemistry. Dr. Fletcher attended meetings of
the National Academy of Science, November
17 to 19, in Washington. He also visited Rut-
gers University.

A. R. Kemp, rubber technologist and insulation
engineer of the Chemical Laboratories, has
been designated one of the country’s ten ablest
chemists in the field of rubber chemistry by
his fellow-members in the American Chemical
Society.

Lioyp EspeNnscHiep spoke on The Dawn of
Electrical Experimentation on November 12
at a supper meeting of the Institute of Radio
Engineers, New York Section, preceding the
technical meeting.

C. H. Townes spoke on Microwaves at a joint
Harvard-M.1.T. seminar at Cambridge.

C. Kirre. selected Paramagnetic Resonances
for his topic when he spoke to the Physics
Colloquium at Rutgers University.

In 1942, Nelson E. Sowers’ health would
not permit him to remain longer in the New
York area, so he was granted a Disability
Pension which allowed him to withdraw from
Radio Research and live in the southwest.
Three years later he went to work for the
Army Ground Forces Board at Fort Bliss,
Texas, as a Mathematical Data Analyst. Re-
cently he has received from the War Depart-
ment a Decoration of Exceptional Civilian
Service. The citation, signed by the Secretary
of War, reads: “His outstanding service in
the development of instrumentation and com-
puting equipment and procedures for antiair-
craft artillery service testing constituted a
contribution of inestimable value to the mis-
sion of his command.”

Mr. Sowers’ friends will be gratified to learn
that his health has been restored. However,
family reasons require his continued residence
in the southwest, so he has now resigned from
the Laboratories.

GeorcE B. Tuomas, until last summer Per-
sonnel Director, is now chief of the Industrial
Relations Department of the Los Alamos lab-
oratory of the Atomic Energy Commission.

JosepH P. MAxFiELD, who retired in Sep-
tember, is now a consulting engineer on the
staff of the Altec-Lansing Corporation, acous-
tic engineers. His headquarters will be on the
Pacific Coast.

CATHARINE C. MAULL, who retired in Oc-
tober, 1945, from Personnel, is curator of the
museum in the Zwaanendael House in Lewes,
Delaware. This building is a replica of the
town hall in Hoorn, Holland.

News Notes
J. R. Haynes presented an invited paper be-
fore the Houston meeting of the American
Physical Society entitled Behavior of Photo-
electrons in Silver Chloride Crystals Exhibited
by Colloidal Silver Produced at Electron Traps.

G. T. Kouman, A. N. W. L. Bonp
and §. O. Morcan discussed crystal growing
problems at the Squire Laboratory.

J. R. Fiecat, G. T. Kouman, N. Y.
MAN and G. K. TEAL visited the Norton Com-
pany in Worcester, where they discussed sili-
con carbide varistors. Mr. Kohman has been
appointed to represent the Laboratories on the
N.R.C. Committee on Design, Construction
and Equipment of Laboratories.

L. H. Germer and F. E. Haworru partici-
pated in a colloquium on Electrical Contacts
at Massachusetts Institute of Technology.

A. R. Kemp discussed plastic sheathing with
cable engineers at Hawthorne during his
week’s visit to that plant.

J. R. TownseEnp visited The Mountain States
Telephone and Telegraph Company, Denver;
the Northwestern Bell Telephone Company,
Omaha and Minneapolis; and the Southwest-
ern Bell Telephone Company, St. Louis, where
he spoke to telephone personnel on Materials
Developments. During his trip, Mr. Townsend
visited the University of Colorado at Boulder,
Colorado. At Washington University, St. Louis,
he addressed a joint session of the American
Institute of Chemical Engineers and American
Society of Mechanical Engineers. In Los Ala-
mos, New Mexico, he addressed the local chap-
ter of the American Society for Metals on
Metals and Alloys for Magnetic
and Electrical Applications.

V. T. CALLAHAN and R. R.
Gay visited repeater stations
associated with the New
York-Boston radio relay proj-
ect regarding power items.
Mr. Callahan also visited the
General Motors Corporation
in Detroit and the Duplex
Truck Company in Lansing
in connection with Diesel and
gasoline engine sets.

W. BaBINGTON witnessed a series of die cast-
ing experiments at the Precision Casting Com-
pany in Syracuse. He also went to Hawthorne
for die casting discussions.

E. E. SCHUMACHER and I. V. WiLLiAMs made
an inspection trip to the School of Mineral
Industries at Pennsylvania State College.

H. A. Brrpsauu visited the International Busi-
ness Machines Company at Endicott, N. Y. He
also attended the meeting of the A.S.T.M.
Committee D-6 on paper and paper products
at Albany. With D. A. McLEan he attended
the open house meeting of the Textile Re-
search Institute at Princeton; and with K. G.
CouTLEE, J. J. MARTIN, G. DEEc and R. Burns,
the meeting at Atlantic City of Committee D-9
on electrical insulating materials.

F. G. Foster received Honorable Mention in
the metallographic exhibit at the recent Na-
tional Metal Congress and Exposition at Chi-
cago for his entry of a chart with eighteen
photomicrographs.

R. Burns’ trip to Massachusetts Institute of
Technology at Cambridge concerned new de-
velopments in mechanical testing of plastics.

W. O. Baker delivered an invited lecture at
Northwestern University, Chicago, on The Or-
ganic Structure and Physical Nature of High
Polymers. The lecture was one of a series spon-
sored by the university. Mr. Baker visited
Hawthorne en route for casting resin develop-

ment conferences. He also was in Washington
for an advisory panel meeting called by the
Office of Naval Research and the Bureau of
Ordnance concerning polymer research.

C. C. Hipxins and J. C. Osten attended the
convention of the Federation of Paint and Var-
nish Production Clubs in Atlantic City. Mr.
Osten’s paper, A Comparison of Infra-red and
Convection Oven Baking, which was presented
at the convention, received the first award.

G. N. THayer addressed the New York Sec-
tions of the A.I.E.E. and of the Institute of
Radio Engineers on the New York-Boston Ra-
dio Relay System.

THE FOLLOWING MEMBERS Of the Institute of
Radio Engineers have been elected to the
grade of Fellow by the Board of Directors of
the Institute: M. W. Batpwin, Jr., H. S.
Biack, L. A. MEACHAM and J. R. Pierce.

A. B. Haines, in Rochester on November 19,
attended a meeting of R.M.A. 10C Committee
on power transformers (receiver section). Mr.
Haines and L. W. Kirkwoop were at Wright
Field in connection with the development of
high operating temperature transformers.

J. R. Weexs and R. K. Evenson attended
conferences at Hawthorne on the aluminum
can condenser problem.

W. R. NEeEIssEr observed the assembly at
Archer Avenue of a trial lot of networks for
the new combined set.

During the next few months, some members of the Laboratories may be spending their
vacations in Florida. A number of retired members live in Florida and would be glad
of a visit, particularly from those who have known them in their more active days.

Eau Callie
Bruce Freile Box 126
Eustis
Stanley F. Nelson
Fort Pierce
James L. Crouch P. O. Box 405
January 1948

St. Petersburg
1014 Bay St., NE
Hollander Hotel
4200 4th Ave., North
1151-34 Ave., North
201 6th St., South

Oscar E. Benson
George W. Folkner
Joseph F. Johlfs
Charles W. Keckler
Wm. Scharringhausen

Members of the Laboratories who retired
recently include E. W. Hancock on Decem-
ber 28 and S. W. SuHiteEy on December 31,
both with 43 years of service; ANTON LODER
on December 31, 32 years; and R. J. HEFFNER
on December 22, 29 years.

Roy J. Heffner of the Personnel Department
retired on December 22 following twenty-nine
years of service. After receiving the B.S. in
E.E. degree from the University of California
in 1916, Mr. Heffner immediately joined the
Western Electric Company in Chicago but was
soon transferred to the Engineering Department
in New York. He served with the Air Service
of the U. S. Army from 1917 to 1919 and
when discharged had attained the rank of
Major. For the next two years he was first
Chairman of Engineering Extension at his
alma mater and then Educational Director of
the Hawaiian Department, U. S. Army. In
July, 1921, he joined The Pacific Telephone
and Telegraph Company, where he became
supervisor of employment and training for
men and women in 1924.

Mr. Heffner transferred to the Laboratories
in 1929 and after a year as Assistant Educa-
tional Director, was made Educational Direc-
tor in charge of the employment and training
of members of technical staff, student assist-
ants, drafting assistants and shop apprentices.

From 1936 to 1939, as Assistant Personnel Di-
rector, he was in charge of employment and
training. Since 1939, he has directed the per-
sonnel analysis and planning group.

Sam W. Shiley of Transmission Develop-
ment retired on December 31 following forty-
three years of service. Mr. Shiley joined the
Clinton Street Works of the Western Electric
Company in 1904 where he held several super-
visory positions in the Drafting Department
and was in charge of telephone circuit draft-
ing when it was moved to Hawthorne in 1907.
The following year he transferred to the Engi-
neering Department to participate in the de-
velopment and standardization of telephone
switchboards, distributing frames, and racks.
He was Standardization Engineer when he
came to New York in 1915. Here he took part
in the development of many manual and toll
systems. Mr. Shiley became Laboratory Engi-
neer in the carrier telephone and telegraph
laboratories at the Graybar-Varick building in
1930. Previous to his retirement, he was in
charge of the Transmission Development Lab-
oratory and was also responsible for handling
drawings and specifications of his department.

EpmMunp W. Hancock
Edmund W. Hancock of the Switching De-
velopment Department retired on December
28 following forty-three years of service. His

first work with the Bell System was in con-
nection with installation of manual central of-
fices in the New York area. After several years
with the Installation Department he _trans-
ferred to West Street, and took part in work
on the first machine switching system which
was tried out as a PBX in the West Street
building, and which preceded the panel sys-
tem. He was next engaged in design and
development of the panel semi-mechanical sys-
tem and supervised part of the testing of this
system at the Newark and Wilmington instal-
lations. Later he was in responsible charge
of a group designing selector circuits for the
panel dial system. Beginning in 1926, he con-
ducted field development work in connection
with new features of various telephone switch-
ing systems and investigations of irregular
conditions. In more recent years he has been
associated with the development of the No. 1
crossbar system.

Anton Loder of the Transmission Develop-
ment Department retired on December 31 fol-
lowing thirty-two years of service. Mr. Loder
joined the Development Department in 1914
and worked as an instrument maker on print-
ing telegraph equipment and then on radio
apparatus for the Signal Corps. Later, in 1917,
he left the Company and went with the M. I.
Instrument Company, where he worked on ap-
paratus they were making for the Western
Electric Company. He returned to the Devel-
opment Department in 1919 and for the next
fourteen years was engaged as an instrument
maker with a variety of telephone apparatus,
particularly for transatlantic and ship-to-shore
service. From 1933 to 1938 he was with the
design and wiring group of the Research De-
partment on special wiring and mechanical
work of an experimental nature. He then was

transferred to do the same general type of
work for the broad-band cable group of Trans-
mission Development. Since April, 1946, Mr.
Loder has been with the coaxial systems group
of the same department.

C. C. Hourz inspected manufacturing facilities
and initial production of ceramic condensers
for radar applications at Winston-Salem.

L. W. STAMMERJOHN’S visit to the New York
Transformer Company at Alpha, N. J., had to
do with manufacturing problems on power
transformers for amplifier use.

C. N. Hickman spoke on Rockets at the Deal-
Holmdel Colloquium on December 3 at Deal.
He also lectured to the students of the Air War
College, Maxwell Field, Ala., on December 8.

R. E. PooLte, W. C. Tinus and M. H. Coox
attended the meeting in Washington of the
Navy Industrial Association.

F. L. LANGHAMMER participated in discussions
on components of radar equipment at the
N.R.K. Manufacturing and Engineering Com-
pany in Chicago.

A. K. Bowren and B. O. BRowNE witnessed
tests on an FM antenna tower at the Blaw-
Knox Company, Pittsburgh.

W. W. Brown visited the Western Electric
Repair Shop at Philadelphia to discuss opera-
tors’ chair problems.

R. G. Koontz and W. J. ApAms visited Win-
ston-Salem and Burlington to discuss engineer-
ing and drafting practices for Bell System
Radio Communication equipment.

M. D. Brixt and I. E. Fair attended the Na-
tional Electronics Conference in Chicago, No-
vember 3 to 5.

R. A. Sykes attended the Piezoelectric Com-
mittee meeting of the Institute of Radio Engi-
neers in New York on November 3.

E. B. Woop and N. INsLey visited Hawthorne
to consult with Western Electric Company en-
gineers on switchboard lamp problems.

R. H. Ross studied aircraft radio motors at
A. W. Haydon Company in Waterbury.

F. S. Mat, H. Peters and V. T. WALLDER
witnessed the field splicing of “Alpeth” cable
at Belleville, N. J. Mr. Wallder and J. B.
Howarp conferred at Point Breeze on plastic
compounding methods.

J. P. Guerarp went to Pittsburgh for meetings
of the A.S.T.M. Committee B5 on copper and
copper alloys.

W. P. Smirtu has been reélected Mayor of At-
lantic Highlands, N. J., for another two-year
term. In his twelve years of civic life, Mr.
Smith has been councilman for ten years, a
member of the school board for six, and mayor
for two.

M. S. Mason, in his capacity as a member of
the New York Engineers Committee on Stu-
dent Guidance, met students of the Bronx High
School of Science on December 3 to discuss
preparation for and opportunities in the engi-
neering profession.

D. E. Trucxsess and M. A. Froserc investi-
gated noise conditions in connection with the
use of the new 100-ampere selenium rectifier
at Buffalo and Erie.

E. M. ToiMaAn recently received a Ph.D. de-
gree in Chemistry from Columbia University.
Dr. Tolman presented his thesis as a paper
before the September meeting of the Ameri-
can Chemical Society in New York City.

W. C. KirkMan is treasurer of Troop Commit-
tee No. 114 of the Boy Scouts of America
in Rochelle Park, N. J. In the campaign just
concluded for funds for the Council, Mr. Kirk-
man’s committee doubled the quota set for
their area.

H. O. StecmMunp spoke on the subject of
Rockets at a meeting of the American Society
of Mechanical Engineers on November 20,
and on December 3 before the New York
Chapter of Alpha Chi Sigma.

A. C. PETERSON discussed mobile radio equip-
ment problems with Motorola engineers at
Chicago.

W. Strack visited Chicago in connection with
the multi-channel mobile telephone system.

A. E. Rupprex and F. J. Skinner visited Al-
bany to discuss problems concerning the New
York State Police mobile telephone system.

O. J. MorzENTI went to Media and Duluth in
connection with equipment development prob-
lems concerning No. 5 crossbar system.

R. L. Lunsrorp conferred at the Northern
Electric Company, Montreal, on studies of
small community dial offices.

J. R. Srone participated in discussions on
ringing equipment for No. 5 crossbar system
at the Holtzer-Cabot Electric Company in
Boston.

A. A. BurcEss and R. P. Jurson, at Philadel-
phia, conferred with local telephone engineers
on special equipment for the No. 5 crossbar.

H. H. Spencer tested electronic speed regu-
lators for motor-generator sets used to supply
power for the L carrier system at Dallas, Min-
eral Wells, and Sweetwater, Texas.

Following an illustrated lec-
ture in the West Street Au-
ditorium on Night Photog-
raphy by Stanley Rayfield
of Life Magazine, forty-
eight members of the Pho-
tography Club took a field
trip to Central Park. Putting
into practice the techniques
outlined by Mr. Rayfield
were this group of photog-
raphers taken by Chairman
W. S. Suydam. Left to right,
K. L. Warthman, A. L. Johns-
rud, R. Olsen, R. J. Nielson,
two unidentified guests, W.
J. Rutter and H. J. Braun

P. T. Sprout discussed television switching
problems with engineers of the Illinois Tele-
phone Company in Chicago.

J. L. Merrity, Jr., and J. A. WELLER con-
ducted a trial installation of the E-1 exchange
area repeater in Chicago. G. C. ReErer ob-
served the installation and performance of
these repeaters.

R. E. Crane attended the Midwest General
Meeting of the A.I.E.E. and the National Elec-
tronics Conference in Chicago during the pe-
riod from November 5 to 7. He presented be-
fore the A.I.E.E. a paper, Frequency Division
Techniques for a Coaxial Cable Network, of
which he was co-author with J. T. Dr1rxon
and G. H. Huser.

Mr. Stoller, who was a member of the Tech-
nical Staff in the Switching Apparatus Develop-
ment Department, was stricken on his way to
work and died shortly afterwards at a nearby
hospital. A native of Schenectady, he had re-
ceived his E.E. degree from Union College in
1913 before joining the Bell System. After a year
in relay development work, he returned to his
alma mater and received his M.S. degree in
electrical engineering in 1915. Returning to the
Physical Laboratory, he was engaged in mis-
cellaneous research problems until World War
I, when he designed and developed power
equipment for radio apparatus used on air-
planes and submarine chasers.

Mr. Stoller then transferred to what is now
the Commercial Products Development De-
partment, where he was responsible for the
development of synchronizing and speed con-
trol devices for sound recording and reproduc-
ing systems for television and for picture trans-
mission. Following that, he engaged in the de-
velopment of electromagnetic apparatus for
switching systems.

During World War II he contributed to the
research and development of the electrical gun
director, magnetic mines and sonar. The more
than seventy patents that he held on voltage
and speed regulators and on sound picture
equipment attested to the valuable contribu-
tions he had made in his various fields of in-
terest. Mr. Stoller was author of numerous arti-
cles in technical publications.

Mr. Kopetz, who was born in 1872, was
transferred from the Manufacturing Depart-
ment of the Western Electric Company to the
Model Shop of the Engineering Department in
1908. Prior to World War I he worked on ma-

chine switching equipment and was one of a
group of instrument makers assigned to install
the semi-mechanical switching system in the
Market and Waverly exchanges in Newark.
During World War I he became a supervisor
of a group of instrument makers.

Mr. Kopetz retired March 1, 1926, and thus
became the first employee to be pensioned
under the benefit plan which was established
when the Laboratories was incorporated in 1925.

Shortly after retirement, Mr. Kopetz, with his
wife and two children, moved to a small farm
in Greene County in the Catskills. Now both
children are members of the Murray Hill Lab-
oratories; Edward is an instrument and _ tool
maker in the Development Shops, and _ his
daughter, Mrs. Elsie K. Melroy, a clerical su-
pervisor in Central Files.

Mrs. Force joined the Plant Department of
the Laboratories at Murray Hill on October 22,
1942, as a member of the Restaurant staff. For
the past two years she had been making salads
at the Cafeteria counter, where she was a fa-
miliar figure to the patrons.

35 years E. F. Helbing W. C. Burger Dorothy Patchell CC. H. Rumpel
M. J. Kelly H.N. Christopher H. R. Vail J. D. Tebo
C J. Mazzi F. De Zavala C. A. Webber C. G. Wennerberg

30 years R. F. Elliott 20 years 15 years
A. O. Adam, Jr. Elizabeth Viggers J. R. Erickson E. F. Billman Theresa Marion
Phyllis Barton Richard Haard J. H. Harding
J. D. Beatty 95 H.W. Heimbach ©, M. Hovgaard 10 years
M. E. Ellis » Gears I. M. Kerney A. F. Klare F. C. Cathers
P. B. Findley A. J. Aikens E. H. Leonard M. R. Kleist C. S. Jackson
J. C. Gabriel Erland Anderson V. L. Lundahl Bernice Potwin —_‘J. A. Miller
Rosario Gerardi E. T. Ball Ethel McAlevey Mildred Ralph Alma Ostar
T. B. Grant B. G. Bjornson D. S. Myers H. G. Raupp Muriel Walter

*Lillian Benjamin—Earl W. Fraser
*Marcae Bitowf—James G. Carolan
Shirley Littman—*Bernard Litwack
*Janet Mysel—Ralph Sinclair

*Members of the Laboratories. Notices of engage -
ments and weddings should be given to Mrs. Helen
McLoughlin, Room 803C, 14th St., Extension 296.

At Buruincton, L. Vietu, F. S. Corso and
R. BLAcK were concerned with production of
the new broadcast microphone; F. L. Crutcu-
FIELD, matters relating to the high quality
moving coil receiver; T. H. CRABTREE, testing
problems associated with hearing aids; and
L. Vieth, the manufacture of the new broad-
cast microphone.

H. F. Hopkins attended the meeting on Loud-
Speakers of the Sound Equipment Section of

J. R. Power, J. M. Rocte and F. S. Corso vis-
ited the Western Electric hearing aid dealers
in Boston, Detroit and Washington in connec-
tion with the field trials of hearing aid cords.

F. L. CruTCHFIELD was at the Archer Avenue
plant regarding problems on the new opera-
tors’ receiver.

F. F. FARNsworTHu visited a number of plants
in the Pacific northwest area that produce and
treat poles, crossarms, and other timber prod-
ucts for Bell System use. He also discussed
current outside plant development projects
with interested engineers of the Mountain

States Company at Denver and The Pacific
Telephone and Telegraph Company at Port-
land, Seattle, San Francisco and Los Angeles.

J. W. Kenarp and R. P. AsHBauGH visited
Hawthorne and the Illinois Bell Telephone
Company for discussions pertaining to the new
types of composite sheath that is being used
for exchange area cable.

A. H. HEARN was in Washington in connection
with a special committee assignment to revise
and reissue the present Manual of Standards
of the American Wood-Preservers’ Association.
At Orville, Ohio, he supervised experimental
treatments of Douglas fir poles to prevent
bleeding. Mr. Hearn, G. Q. LumspEN and
R. H. Couey inspected creosoted southern
pine poles in the Harrisburg area.

F. E. Warp appeared before the Board of Ap-
peals at the Patent Office in Washington rela-
tive to an application for patent.

O. H. Coo.inceE, at Milwaukee, spoke on
Transmission Line Theory at a six-lecture sym-
posium on telephone and radio transmission
under the auspices of the Milwaukee Section
of the Institute of Radio Engineers.

W. HarTMANN attended the fall meeting of
the Optical Society of America in Cincinnati,
October 23 to 25, at which he presented a
paper, co-authored by B. E. Prescott, The
Quantitative Spectrochemical Determination of
Barium, Strontium, and Calcium.

A. E. Jounson, M.D., of the West Street Medi-
cal staff, has recently completed four articles
in a series of ten for the Encyclopedia Ameri-
cana. Dr. Johnson’s subjects include Penicillin
Aerosol; Recent Advances in Tuberculosis; and
Pulmonary Physiology.

C. B. H. FeEtpMan, H. J. FisHer, M. D. BRILL
and I. E. Fair attended the National Electronics
Conference, November 3 to 5, in Chicago.

J. R. Power participated in conferences at the
United States Naval Hospital in Philadelphia
on hearing aid problems.

B. E. Stevens conferred at the Magnetic
Windings Company in Camden on magnetic
materials for power transformers manufactured
at Winston-Salem.

J. R. Power and F. S. Corso were in Chicago
in connection with initiating a field trial on
hearing-aid receiver cords.

Wuat KIND of men are the 2,300 scientists and engineers of Bell ‘Tcle-
phone Laboratories?

Men of many types, working in different ficlds of research, may
contribute to each development.

But all have certain characteristics in common: Good minds as a
foundation, many years of learning in the fundamentals of their science
and the methods of research, and a co-operative attitude — for without
co-operation of individuals these products of research could never be
produced.

Above all else, however, they have “the spirit to adventure, the wit
to question, and the wisdom to accept and use.”

That kind of men can produce the finest telephone equipment in the
world — and have done so.

BELL TELEPHONE LABORATORIES eExpioriNG AND INVENTING, DEVISING
AND PERFECTING FOR CONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE

Bell Laboratories Record  1948-01: Vol 26 Iss 1