it is often important to
pick up sounds coming from a par-
ticular direction to the exclusion of
other sounds such as reflections,
audience noise, camera click or feed-
back from loudspeakers. For these
situations the microphone should be
more sensitive to sounds coming from
the desired direction. In a model
that has recently been developed in
these Laboratories, there is a possible
discrimination of 20 db against un-
wanted sounds.

The new microphone, known as the
Western Electric No. 639AA, uses a
diaphragm transmitter and a ribbon
transmitter in combination. The rib-
bon type operates on the difference in
pressure developed by the sound wave
between the front and back of a

ribbon which moves only in the direc.
tion perpendicular to its surface. The
effective force on the ribbon, for
sound approaching at some angle to
this direction, is proportional to the
cosine of that angle. When sound
strikes the ribbon on edge the pres.
sure is the same on both sides; there
is no motivating force and no re.
sponse. This gives the directivity a
two-looped characteristic which jis
shown by the dotted lines in Figure 1,
The motion of the ribbon is in phase
with the motion or velocity of the air
particles, hence the term “velocity”
microphone is frequently applied to
the ribbon type. The control obtain-
able with this type alone is limited,
however, because unwanted sounds
very often come from the opposite
direction from the desired sounds and
not at right angles to them.

A pressure-type microphone con-
sists essentially of a movable dia-
phragm closed on one side by a hollow
housing. When the sound pressure in-
creases outside of the diaphragm it
moves inward. This motion depends
on the pressure at the outer surface
and not on the direction from which
the sound comes, since the sound
flows around the housing. The pres-
sure type is essentially non-directional
and diaphragm’s motion is in phase
with the pressure in the sound field.

pressure microphone is 180 degrees
out of phase with one of the loops of
the ribbon microphone, that loop can
be cancelled. The response of the
other loop will be increased then, be-
cause the ribbon reverses its direction
of motion as the source moves through
the plane of zero response, while the
output of the pressure microphone
does not change. The output of the
two together has the shape shown by
the solid line in Figure 1. Due to the
fact that it is heart shaped, this curve
has been called the ‘‘cardioid” and
this characteristic is a satisfactory
approximation to that desired for a
directional microphone.

Combining a ribbon and dynamic
instrument is complicated in practice
because neither type follows com-
pletely the simple conditions as-
sumed above. The size of the elements
required to give an adequate output
level is so large that the dimensions
are not small compared with
the wave length of the sound
at the higher frequencies, and
these sounds will not flow
around the microphone. The
magnitude and phase of the
outputs is not the same over
the frequency range, hence
cancellation of one response
loop of the ribbon microphone

highly efficient alloy steel. The hous-
ing of the dynamic unit was re-
shaped and streamlined so that its
presence does not affect the opera-
tion of the ribbon. This housing en-
closes also the ribbon transformer and
a three-way switch as illustrated in
Figures 2 and 6. It supports the
wind-screen housing for the ribbon
and provides the mounting and termi-
nal facilities in the form of a pro-
jecting plug. The result is the micro-
phone shown in the headpiece, a
compact instrument smaller than the
usual ribbon microphone of com-
parable efficiency. Its overall height,
including the plug terminal mounting,
is 7% inches; and it weighs approxi-
mately 314 pounds. The housing of
the microphone is made of cast
aluminum finished grey with the
horizontal lines in polished metal.
The cardioid microphone can be
mounted either on a floor or a desk

cannot be achieved in simple
fashion. By incorporating new
design features and careful
equalization, however, a satis-
factory solution of these diffi-
culties was attained.

A compact pressure type
unit was already available in
the Western Electric 630A* or
633Af microphones. A special

dotted lines; the characteristic of the cardioid micro-
phone by the solid line

the cardioid directional
characteristic. Thus
the cardioid is three mi-
crophones in one: non-
directional dynamic, bi-directional
ribbon and cardioid-directional when
the two elements are used together.

WIND
SCREEN MAGNET,
>
RIBBON->
PLATE
AND —>
BAFFLE
MAGNET,
ACOUSTIC
YA DYNAMIC RESISTANCE
HOUSING
|
DIAPHRAGM
RIBBON
TRANSFORMER] =
INN =
TERMINAL
PLUG
AND
MOUNTING

Fig. 2—Simplified cross-sectional view of
the cardioid directional microphone

Fig. 3—Typical response characteristic of a combined
unequalized-dynamic and ribbon microphone

To increase the stability of the rib-
bon a new design was developed for
the velocity microphone by W. R.
Harry of the Laboratories Staff. This
ribbon is thicker than usual and has a
cylindrical curvature over most of its
length. It is corrugated at each end
so that it acts like a bar with spring
supports and by this means other
modes of vibration than the funda-
mental that may be encountered are
effectively suppressed.

Besides achieving a smooth re-
sponse, which matches that of the
dynamic both in magnitude and
phase, the stiff ribbon reduces wind
noise to a level approximately ten db
lower than that of other ribbon micro-
phones. This permits using the micro-
phone more freely outdoors where
breezes are often unavoidable. Dam-
aging the ribbon, by exposure to a
sudden gust of wind, is also unlikely
especially since mechanical stops have
been provided in order to prevent its
motion beyond the elastic limit of
the material.

In Figure 3 is illustrated the re-
sponse for 0° and 180° incidence of a
typical combination of dynamic and
ribbon elements when connected with-

15 over the frequency
-80 ssamaaens range from 40 to 10,000
cycles and there is
4 hard] ib]
Ban's. ardly any perceptible
| quality change for any
WN, angle of incidence up
w-100 W to 120 degrees. The
quality of the response
at angles greater than
120 degrees is of little
’ importance because the
500 1000 2000 5000 19900 Sensitivity in this re-
FREQUENCY IN CYCLES PER SECOND

out equalization. The curves cross at
about 7000 cycles and at low fre-
quencies they come close together, be-
cause the electrical outputs of the
two elements are out of phase at these
frequencies. To correct this limita-
tion and extend the useful range to
10,000 cycles a network was designed
by Mr. Harry. The improvement is
shown in the response curves of the
equalized microphone, Figure 4.
The output level of the cardioid
microphone is unusually high, eighty-
four db below one volt
per dyne per square
centimeter. This level
is four to six db higher
than that of the West-
ern Electric 630A or
633A dynamic types
and only two db lower
than that of the highly
efficient Western Elec-
tric 618A dynamic mi-
crophone. The new mi-
crophone is designed
to operate into an im-
pedance of from thirty
to fifty ohms. The
normal-incidence re-
sponse of the cardioid
combination is smooth

gion is low. The per-
formance of the dy-
namic and ribbon mi-
crophones when used
alone is similar to that of other
commercial instruments of their re-
spective types.

A visual indication of the variation
of sensitivity with angle is given in
the chart of Figure 5 by shading from
light to dark. The “wide pick-up”
zone of 120 degrees represents the
region in front of the microphone
where there is practically no variation
in quality or sensitivity. In the
“fading” zone from 60 degrees to
150 degrees on either side the sensi-

Fig. s—Chart illustrating the directional characteristics of
the 639A cardioid microphone

tivity changes rapidly with angle and
care must be exercised to keep within
range of the microphone. Sounds are
discriminated against by approxi-
mately twenty db in the dead zone of
60 degrees behind the microphone.
In addition to these three principal
zones, the sector from 60 degrees to
go degrees on either side has been
selected as the “announcer’s”’ or close
talking zone. Since the ribbon micro-
phone contributes very little in this
sector, the characteristic ““boomy”
reproduction of unequalized ribbon
microphones has been avoided.

In sound studios and public addresg
installations the directional charac.
teristics of the cardioid microphone
are particularly useful. When located
near a studio wall it suppresses sound
reflected from behind; and in q
theatre it automatically divides the
audience from the stage, thus elimi-
nating noise and reducing feedback
so that more sound reinforcement can
be used. The microphone has been
thoroughly tested under practical
conditions which have demonstrated
its superiority in pick-up situations
long baffling to sound engineers.

OME metals, notably sodium,
potassium, cesium and others
of the alkali group, liberate elec-
trons freely when light falls on them.
This behavior is the basis of photo-
electric cell activity; it has been
studied in detail not only on this
account but also because it bears on
recent theories of the metallic state.
Between the photoelectric and the
optical properties of a metal there
exists so close a relation that the
photoelectric behavior of a metal can
be predicted from its index of re-
fraction and its absorbing power for
light. These optical constants can be
found by allowing a beam of plane
polarized light to fall on a polished
surface and determining how much
the incident light has been elliptically
polarized by reflection. Previous meas-
urements of these constants for the

alkali metals have been confined to
the visible spectrum but the Labora-
tories has extended them into the
ultraviolet region where the maxi-
mum photoelectric emission occurs.

Elliptically polarized light may be
thought of as consisting of two beams
of light plane polarized at right
angles and differing both in phase
and amplitude. With an optical de-
vice, called a Babinet compensator,
which retards one of these beams more
than the other, elliptically polarized
light can be restored to plane po-
larized light. The compensation re-
quired to do this measures the phase
shift on which the ellipticity depends.
The azimuth of the plane of vibration
of the restored light differs from that
of the incident light and the difference
can be measured in the visible range
with an analyzer of the Nicol prism

type. This prism extinguishes plane
polarized light entirely when the plane
of vibration is oriented at right
angles to certain crystallographic di-
rections in the prism.

By substituting values of the phase
shift and azimuth in equations as
developed by Drude or by T. C. Fry
there may be found the index of re-
fraction N of a metal, and the ex-
tinction coefficient K, which measures
the damping the light experiences on
entering the metal. With the values
of n and xk, for a particular wave-
length there can be calculated the re-

Fig. 1—Dispersion measurement curves of
the index of refraction, N, for sodium,
potassium, rubidium and cesium

flecting power, transmission for va-
rious thicknesses, and the absorbing
power of the metal either in bulk con-
dition or as a thin film supported by
another metal. The last is of special
interest because the photosensitive
surfaces of ordinary photoelectric
cells are of this type. Experiment
shows that the rate of emission of
photoelectrons from such a surface
is proportional to the rate at which it
absorbs light.

In the ultraviolet region the method
of measurement must be modified so
that phase and azimuth changes are

accomplished by a pair of optical
wedges, one of right and the other of
left rotary quartz, which are intro.
duced between the Babinet compen.
sator and the Nicol analyzer. The
result is a rectangular pattern of dark
spots on a bright background which
may be recorded photographically, 4
comparison of the spot patterns for
light before and after reflection from
the metal surface shows that each
spot of the reflection pattern has
undergone a shift from the position it
occupied before reflection. By analy-
sis the x-component of the shift may
be identified with the phase change
introduced by reflection, and the
y-component with the azimuth change,
or the rotation of the plane of vibra-
tion. These two measurable quan-
tities when substituted in the Drude

Fig. 2—Dispersion measurement curves of
the extinction coefficient, K,, for sodium,
potassium, rubidium and cesium

Mirror surfaces of alkali metal
have to be prepared in vacuum and
rotected from the air to prevent
oxidation, which dulls them. For
measurementson potassium and rubid-
ium, a heavy deposit of the metal
was collected on a quartz plate in an
exhausted bulb. The metal surface
was protected by covering it with a
second plate while still in the ex-
hausted bulb, by raising the second
plate by magnetic action on the iron

Fig. 3—Reflecting power at normal inci-
dence for sodium, potassium, rubidium
and cesium

tip at the lower end of its holder. A
strain-free 60-degree quartz prism
was then sealed to the upper plate
with paraffin oil; and the edges were
protected with parafin wax, where
the alkali metal was exposed. Meas-
urements could then be made in air.

In a second method, used for
sodium and cesium, the metal was de-
posited on an optically flat surface
enclosed in an evacuated bulb which

Fig. 4—Rate of absorption of energy for
equal thickness (ca. 10° cms.) of sodium,
potassium, rubidium and cesium on plati-
num-iridium. Light incident at 60 degrees,
polarized parallel to the plane of incidence

was provided with quartz windows.
The arrangement had the advantage
that reflection occurred at the free
surface of the metal under investiga-
tion but special precautions were
necessary to provide that sealing and
evacuation of the tube should not
produce strains in the windows.

The values of N and kK, computed
from measurements of the phase shift
and the azimuth of the restored beam
of plane polarized light are shown in
Figures 1 and 2. In the visible range
sodium has the lowest index of re-
fraction and the highest extinction
coefficient of the group, potassium is
next, followed by rubidium and
cesium. The relative values of N and
K, in the ultraviolet are reversed, the
extinction coefficients being low and
the refractive indices higher.

Figures 3 and 4 show properties of
the alkali metals, calculated from the
values of their optical constants.

Figure 3 gives the reflecting powers
for normal incidence. The wave length
for which nN =k, divides the range of
high reflecting powers from that of
low reflecting powers.

The rate of absorption of energy by
thin films of the alkali metals de-
posited on platinum-iridium is illus-
trated in Figure 4. The absorption is
moderately selective in cesium; be-
comes increasingly so for rubidium
and potassium, and is extremely high
in the extrapolated range for sodium.
The wave length for which n =k, here
gives the peak absorption.

A comparison between the rate of
absorption of energy and the rate of
emission of photoelectrons is of par-
ticular interest. Rubidium illustrates
this correlation. Curve 1 of Figure 5

shows the photoelectric emission of a
thin film of rubidium on platinum.
iridium and Curve 2 gives the calcy.
lated rate of absorption of energy at
the surface of such a film, 10~ ems.
thick. Part of the energy absorbeq
at the surface of the metal is ey.
pended in effecting the escape of the
photoelectrons. The amount may be
calculated approximately by multi.
plying the ordinates of Curve 2 by a
factor which depends on the longest
wave length at which rubidium emits
photoelectrons. Curve 3, in which this
correction has been carefully incor.
porated, fits Curve 1 closely and go
shows conclusively that the photo-
electric emission of thin films may be
accurately predicted from a knowl.
edge of their optical constants.

Fig. s—Comparison of photoelectric emission and calcu-
lated energy absorption of rubidium on platinum-iridium

between the line and both the
transmitter and receiver. A function
of the two-winding transformer, which
has been widely used in this set, is to
improve the efficiency of these con-
nections. With such an arrangement,
the subscriber hears not only the
speech coming over the line from the
distant end, but also his own speech,
since the voltages generated in the
transmitter by his voice affect his
own receiver. The sound picked up by
a transmitter and heard through its
associated receiver is called “‘side-
tone.” It is possible, however, to
design the circuit of a two-way tele-
phone set so that under ideal condi-
tions the sound picked up by the
transmitter is not heard through the
associated receiver. Such an arrange-
ment, known as an anti-sidetone cir-
cuit, involves some complications
over the two-winding transformer cir-
cuit. In recent years an anti-sidetone
subscriber set employing a three-
winding transformer has come into
wide use in the Bell System.

Sidetone has several detrimental
effects on telephone transmission. A
person naturally regulates the volume
of his speech by the apparent loud-
ness of his own voice in his ear.
The presence of sidetone increases
the apparent loudness, and there is a
tendency to decrease his talking
volume, which reduces the level of
the outgoing voice signals. Sidetone
also interferes with incoming trans-

mission, because it allows room noise,
picked up by the transmitter, to
mingle with and partially mask the
incoming speech.

The first anti-sidetone circuit in
commercial use was invented by
C. E. Scribner in 1893, and was used
for some of the operator telephone
sets. In 1906, G. A. Campbell showed
that there were a large number of
possible anti-sidetone circuits em-
ploying a single transformer and a
single balancing network. To be prac-
ticable for general use, the circuit
must be applicable to existing condi-
tions and apparatus, and should re-
quire a minimum of additional ex-
pense. Considerable development
work was necessary to secure an ar-
rangement which provided the de-
sired transmission improvements, and
which, at the same time, could be
economically incorporated in new or
existing telephone apparatus. The
circuit adopted meets these various
requirements and _ necessitates—be-
sides the equipment of the sidetone
subscriber sets—an additional con-
denser, an additional winding on the
transformer, and, where the com-
bined station set is not used, one
extra conductor in the cord to the
telephone set.

current to the path through the
transmitter when the set is in use.
Omitting the bell and the switchhook,
which play no essential part under
talking conditions, this circuit can be
arranged schematically as shown in

the middle sketch. Since the receiver
and the B winding of the induction
coil are in series, they can be inter-
changed in position without affecting
the operation of the circuit; and since
the condenser, under ideal conditions,
would be of infinite capacitance, it
would have no effect on the talking
circuit and may thus be omitted in
this explanation of the operation of
the circuit. With these two changes
the circuit would be as shown in the
lower sketch.

Under talking conditions, a voltage
—marked Eo on the diagram—is
generated across the transmitter. Cur-
rent flows through the transmitter
from I to 2, where it divides—part,

marked 1, passing out over the line.
and part, marked Is, passing around
the circuit including the receiver, |;
is the latter current that causes the
sidetone. Received speech current
also will pass through both the trang.
mitter and the receiver.

For many years a modified ar.
rangement of this circuit, known as
the sidetone-reduction connection and
involving only a simple interchange of
connections, was frequently used on
the shorter station loops to obtain a
reduction of sidetone, although it js
not strictly what is termed an antj-
sidetone circuit. The arrangement js
shown in Figure 2. It gives a reduc.
tion in sidetone of about 7 db, and a
gain in receiving efficiency of about
1 db, but it causes a loss of about 5 db
in transmitting efficiency.

In the anti-sidetone set now being
employed, the sidetone circuit is
modified by shunting another path
around the receiver, as shown in
Figure 3. In this anti-sidetone circuit
also, under transmitting conditions
shown in the lower diagram, the cur-
rent from the transmitter divides—
part going over the line and part
around the local circuit. If the addi-
tional circuit element, consisting of
winding c of the transformer and the
network n, can be made to carry all
of 1s, however, there will be none left
to pass through the receiver, and
there will thus be no sidetone. This is
exactly what this additional circuit
element is designed to do; and al-

Fig. 2—Schematic of sidetone reduction
circuit used for short station loops

though under commercial conditions
the action is not perfect, the sidetone
is greatly reduced.

This condition, and the further con-
dition that there shall be no current
in the network during receiving, is
brought about by a proper design of
the windings A, B, and c and the
network N in relation to the im-
pedances of the receiver, transmitter,
and line. The calculations, and the
relationships that must exist, are
somewhat complicated, but the quali-
tative behavior of the circuit is not
dificult to see.

In the lower diagram of Figure 3,
which shows the transmitting condi-
tion, arrows indicate the relative
directions of current flow at an ar-
bitrary instant. The windings are
so poled—a and B in the same sense
and B in the opposite sense—that the
voltage E, tends to make current flow
through the network to an amount
just equal to the current I; flowing
through winding B. Hence no current
flows to or from the junction (4) in the
branch which contains the receiver.
Another way to visualize the situation
is to consider that the circuit is de-
signed so that the voltage drop from
point 2 to point 4 is just equal to the
drop from point 2 to points I or 3.
As a result there is no voltage drop
from point 4 to point 3 and no current
flows through the receiver. As already
pointed out, these ideal conditions are
not completely met, but the sidetone
current that passes through the re-
ceiver is greatly reduced.

For received speech, the relative
directions of the currents in the cir-
cuit are shown by the arrows in the
central diagram. The currents in
windings a and B, as in the trans-
mitting case, induce opposing volt-
ages in winding c, the voltage from
winding a being the greater. The net

voltage in winding c is just sufficient
to counteract the tendency of the volt-
age drop across the receiver, due to
the current Is, to send a current
through the network. As a result
there is no current in the network
during receiving, a condition which
must be fulfilled if the circuit is to be
ideally efficient.

In the actual set, the network Nn
is a simple resistance, and is incorpo-
rated in the winding c, so that there

is no separate physical element in the
circuit corresponding to N. The actual
circuit is shown in the upper diagram.
Instead of using the same condenser
for both ringing and talking, as is
done with the sidetone set, two con-
densers are used—one of small capaci-
tance in series with the ringer and one
of larger capacitance for the talking
circuit. This gives better transmission,

dialing, and ringing performance, and
permits fewer switch-hook contacts.

The new anti-sidetone set is slightly
lower in transmitting and receiving
volume efficiency than is the side-
tone set, since the ideal requirements
can only be partially fulfilled; but its
large reduction in sidetone, amount-
ing to some 10 db, results in an effec-
tive overall gain in transmission of

When, on Fuly 29, 1914, Theodore N. Vail, then President of
the American Telephone and Telegraph Company, took his tele-
phone receiver from its hook in New York and spoke to G. E.
McFarland, President of The Pacific Telephone and Telegraph
Company, at San Francisco, another epoch-making achievement
in telephone communication became a fact.

Previous to 1911, dy using as large wires as were economically
practicable, the telephone would talk reasonably well over a
distance about as long as New York to Chicago. With the develop-
ment and practical application of loading coils this distance was
doubled in 1911 and New York and Denver were interconnected.
The desirability, however, of a transcontinental telephone system
had long been apparent. It was accomplished in 1914 through
extensive research work under the ‘direction of F. B. Fewett.
There was extensive research on transmission lines, on repeater
circuits and on amplifiers for repeaters, all of which culminated
in a transcontinental system.

In the early days of the New York-San Francisco line three
types of repeaters were successfully demonstrated: a mechanical
repeater, a mercury arc repeater and the vacuum tube repeater.
The latter proved to be one of the most powerful and flexible
tools in the communication art; and in succeeding years tt has
been vital in carrier current transmission, transatlantic radio
telephony, radio broadcasting and sound pictures.

HE development of modern
broad-band carrier systems has
required extensive measure-
ments of impedance at transmission
frequencies much higher than those
used for earlier carrier systems. Over
the usual range of impedance, these
measurements are made on the five-
megacycle bridge recently described
in the Recorp.* With this bridge, the
inductance component of the im-
pedance is measured by a capacitance
standard, but for inductances less
than ten microhenrys this method is
unsatisfactory because of the very
large size of capacitance required. To
cover this low range, therefore, a
special inductometer has been de-
veloped for use with the bridge.
The conventional inductometers are
not satisfactory at these high fre-
~ *REcorp, April, 1937, p. 261.

quencies because of the relatively
large distributed capacitance of the
coils. In addition, the large residual
inductance, the limitations of range,
and the low ratio of inductance to
effective resistance at low settings
further restrict their usefulness. The
new inductometer avoids these diffi-
culties by employing a helical coil
whose self inductance is changed by a
trolley contactor that varies the num-
ber of active turns between the
terminals.

As actually constructed, two such
coils are employed to provide elec-
trical symmetry with respect to
ground, which is necessary in measur-
ing balanced circuits. A partition
through the center of the cover, as
shown in Figure 1, completes the
shielding provided by the mounting
plate and cover, so that there is no

Fig. 1—A crank on the front of the inducto-
meter drives the two coils through non-back
lash gears and the sprocket wheel

capacitive or inductive coupling be-
tween the two coils or between the
coils and any adjacent apparatus.

Each coil consists of a number of
widely spaced turns wound helically
on an insulating spool, and a trolley
slides along the turns as the coil is
rotated. The arrangement is clearly
shown in Figure 2. Collector rings, not
evident in the photographs, bring out
a connection from each end of each
coil, and the trolleys are connected to
the terminals connected to one end of
the coils. All of the contact parts are
silver plated to give a low and stable
contact resistance, and the four termi-
nals are brought to coaxial jacks for
connection to the standard high-
frequency bridge.

The coils are rotated in unison
through a crank and non-back-lash
gears, and as the coils rotate the
trolleys slide along the turns of the
coils, giving a continuous adjustment.
Another set of gears on the front of

the mounting plate drives two spools
that carry the film on which the cali.
bration is marked. This film jg
coupled to the coils by a sprocket
wheel mounted on the same shaft as
the crank. The range of inductance jg
from one to twelve microhenrys, and
the film employed is twenty feet long
thus permitting very small changes
to be accurately read. The smallest
divisions of the scale are two-tenths of
an inch apart, and represent a change
of 0.01 microhenry.

Since with the construction em.
ployed only that part of the coil neces.
sary for the inductance being meas.
ured is in the circuit, it is possible to
secure a high ratio of induction to
effective resistance. Measurements in-
dicate that settings are reproducible
to within a hundredth of a micro-
henry and to a ten-thousandth of an
ohm of effective resistance.

Fig. 2—A twenty-foot film scale provides
easy reading over the entire range

144th commencement on ‘Fune 12 at which time the honorary degree of Doctor
of Civil Law was conferred upon him

A PROGRAM OF OBSERVATION and tests of the
performance and characteristics of the two-
megacycle coaxial installation between New York
and Princeton has been under way for some time.
This has included measurements of modulation,
load rating, noise and crosstalk, and studies of
transmission variations, pilot-channel charac-
teristics, amplifier-switching arrangements, and
program transmission. As a result of this work,
a number of modifications have been introduced
to improve the system performance. Tests on
the present two-megacycle repeaters between
New York and Princeton will be continued
until about the end of August, at which time
this equipment will be removed.

Plans are under way for a trial, to extend the
entire distance between New York and Phila-
delphia, of new repeater equipment designed to
handle a top frequency of either about 2 mega-
cycles for telephone or about 3 megacycles for
television. This new equipment will be of the

George A. Campbell (right) and Fohn R. Car-
son at the Medal Day exercises of The Franklin
Institute, held in Philadelphia on May 17,
at which they received Elliott Cresson Medals

type which it is planned to install for commercial
service between Stevens Point and Minneapolis,
The new repeaters will be spaced approximately
five miles apart. Construction of this new repeater
equipment is already under way and installation
between New York and Philadelphia will be
started early in July. Later, new terminal equi
ment will be tried out in conjunction with the
3-megacycle repeater equipment.

THE HONORARY DEGREE of LL.D. was con-
ferred on W. H. Harrison, vice-president and
chief engineer of the American Telephone and
Telegraph Company and a director of the Lab-
oratories, by the University of Notre Dame
during the graduating ceremonies held on June
5. Mr. Harrison delivered the commencement
address in which he gave a general discussion of
engineering.

Mr. Harrison has also been appointed a direc-
tor of The Bell Telephone Company of Canada.

The National Committee has received the
reports of nineteen cases in which local Com-
mittees of Award in the various Operating
Companies have awarded twenty-two Theodore
N. Vail bronze medals. These make a total of
1093 medals awarded since the establishment of
the Fund in 1920. The National Committee has
selected from these cases the following for
further award:

A silver medal, with a cash award of $250, to
Jerry Frank Kincannon, exchange repairman,
Southwestern Bell Telephone Company, Miami,
Oklahoma, “for courage, initiative and good
judgment in effecting a rescue and for unusual
competence in the use of first aid under trying
and hazardous conditions.”

A similar award to George F. Wilson, installer-
repairman, The Pacific Telephone and Tele-
graph Company, Grass Valley, California, “for
conspicuous courage, persistence and fortitude
in an extreme effort to save the life of a fellow-
employee under very hazardous conditions
during a blizzard, while engaged in the restora-
tion of telephone service.”

Bronze plaques were awarded, in commemora-
tion of these acts, to both Companies.

Reading clockwise around the table from the extreme left: H. E. Marting, H.C. Spryer, A. W.
Bates, L. W. Tucker, I. H. Moore, H. H. Lowry, H. H. Glenn, L. H. Fohnson, F. R. Shea,
C. G. Stoll (guest), F. M. Williams, O. E. Buckley (guest), D. D. Miller, A. G. Hall, R. L.
Quass, L. T. Marks, G. Dobson, C. W. Lowe, F. R. MacGregor, E. H. Schroeder, F. C. Wright

A special bronze plaque has been awarded to
the employees of the Bell System in recognition
of loyalty, devotion to duty and achievement
during and after the hurricane last September.

On JuNE 9, nineteen members of the Haw-
thorne student group of 1909 lunched together
at West Street with O. E. Buckley and C. G.
Stoll attending as guests. This class was one of
the first large groups to take the students’
training course then offered young college gradu-
ates who elected to enter the telephone field.
The original group numbered 65 men of whom 31
are still in the Bell System. Most of the members
of the group were hired by G. A. Anderegg who
retired from active service in the Laboratories
last year. The Laboratories’ men shown in the
accompanying photograph, taken during the
luncheon, are:

G. Dobson H. H. Lowry
H. H. Glenn H. E. Marting
A. G. Hall D. D. Miller
L. H. Johnson R. L. Quass
C. W. Lowe H. C. Spryer
J.C. Wright
CoLLoguiuM

R. Bown spoke at the last meeting of the
1938-1939 season of the Colloquium on May 22.
He reviewed some of the most recent develop-

ments in short-wave telephony, such as the
musa and single-sideband transmission and dis-
cussed current problems, including horizontally
deviated wave propagation and the development
of a truly multiplex system.

Tue ResearcH Department of the Labora-
tories is making a statistical study of hearing in
the United States by securing photographic
copies of the musical tone test blanks at the Bell
System exhibit at the World’s Fairs. Members of
the Laboratories who have taken the test may
assist materially in this study. Simply write
your name and room number on your test blank
and mail it to H. C. Montgomery, Room 857,
463 West Street. This will be returned to you
promptly and you will be sent a brief question-
naire for additional information to aid in the
interpretation of the data. If you are interested
in following your test at the Fair with a more
detailed laboratory test, Mr. Montgomery will
arrange for such a test insofar as facilities are
available. This request applies only to the test
for musical tones and not for spoken words.

On June 5, Dr. Jewett gave the commence-
ment address, entitled Forty-One Years After
Graduation, at the University of Nebraska.

A. F. Drxon and H. M. Bascom visited Johns-
town, Pennsylvania, on May 22 to inspect an
all-relay automatic exchange which was manu-
factured and installed by the North Electric
Company for the non-Bell telephone company
that gives service in Johnstown. This is the
largest exchange of this type which has ever
been furnished.

R. H. Witson has been appointed General
Service Manager, succeeding J. S. Hartnett
who died on May 1. Reporting to Mr. Wilson
are D. R. McCormack, Central Service Man-
ager; E. V. Mace, Local Service Manager; and
R. E. Merrifield, Merchandise Manager. In the
Plant Department, C. W. Lowe succeeds E. V.
Mace as Building Layout Engineer. At the time
these appointments became effective, May 29,
the Library was transferred from the General
Service Department to the Bureau of Publication,
with Miss L. E. Smith, Librarian, reporting to
John Mills, Director of Publication.

A GROUP LUNCHEON of the supervisors of the
Apparatus Development Department was held
at the Hotel Abbey on May 25. Following the
luncheon, R. L. Jones, presiding at the meeting,
introduced the speaker, W. H. Harrison, who
first summarized progress made in the telephone
business during the past ten years and then
discussed the problems of the future. The com-
mittee in charge of arrangements consisted of
P. S. Darnell, J. B. Dixon, E. C. Edwards,
R. C. Koernig, G. Puller, W. H. Sellew, O. A.
Shann, H. D. Wilson, Jr., and J. M. Wilson.

strated during the Conference of Presidents of
the Associated Companies by A. B. Bailey,
W. K. Caughey and H. A. Hay.

H. T. BupEnzBom was in Washington on radio
equipment problems of the Navy Department.

G. N. Tuayer and W. H. Donerry recently
visited the Hartford plant of the General
Electric Company.

T. E. Lenican supervised the installation of
the s00-watt ultra-high-frequency broadcast
station and the conversion of a 6B radio trans-
mitter for high-fidelity operation at Brooklyn
Technical High School.

F. E. Nimmcke visited Topeka, Kansas, where
he inspected the installation and adjusted the
355E-1 radio transmitting equipment (5 kilo-
watts) at Station WIBW.

E. L. Owens visited the Raytheon Manv-
facturing Company at Waltham, Massachusetts,
to discuss speech input equipment. _

R. H. Miter, on the twenty-seventh of May,
completed twenty-five years of service in the
Bell System. Mr. Miller joined the Western
Electric Company at West Street in 1913 and
almost immediately was sent to the Installation
Department at Baltimore on the installation and
inspection of manual central-office equipment.
For the next few years he worked for the Instal-
lation Department along the entire Atlantic
seaboard. Late in 1916, following a ten-month
leave of absence, he transferred to the Providence
Telephone Company on central-office engineering
and inspection. During the World War he was

with the 4o1st Telegraph Battalion, formed by
the Bell System, and spent fourteen of his
twenty-two months of service in France.

Upon his return to this country, Mr. Miller
spent a short time with the Holmes Electric
Company, a subsidiary of the New York Tele-
phone Company, and then entered what is now
the Equipment Development Department of the
Laboratories. Following a period of special
training both at New York and Hawthorne, he
organized routines for handling relations between
the engineering staff and the clerical force. After
this he spent considerable time with various
operating companies aiding them in preparing
job specifications for newly developed equipment
to be purchased from the Western Electric Com-
pany. From 1925 to 1931 he was the Labora-
tories’ cobrdination engineer handling the instal-
lation of No. 3 toll offices at Cleveland, Detroit
and New York. Since 1931, Mr. Miller has been
in charge of the toll current-engineering group of
the Equipment Development Department.

A FIVE-STAR SERVICE EMBLEM signifying the
completion of twenty-five years of service in the
Western Electric Company and the Labora-
tories was awarded to Frank Wallenius on the
twenty-fifth of May. Mr. Wallenius joined the
Western Electric Company at New York in 1912
and worked on printing telegraph machines.
When the manufacturing organization trans-
ferred to Hawthorne a short time thereafter, he
also went as a group supervisor on the production
of printing telegraph machines. He left the com-
pany in 1916 and for the next two years worked
as a foreman for the Sperry Gyroscope Company
in Brooklyn.

Mr. Wallenius then came to the Development
Shop of the Western Electric Company where he

has since spent most of his time on the making
of accurate instruments and intricate tools and
dies. For the past ten years he has been in the
precision room. Some of the special projects on
which he has worked include the making of light
valves used for the recording of sound pictures
and picture transmission, metal graphs for the
optical-tone generator, and the contour machine
for grinding styli to a radius of 0.001 of an inch.

Frank Howarp GranamM, who completed
twenty-five years of Bell System service on the
twenty-seventh of May, graduated from Penn-
sylvania State College in 1914 with the B.S. in
E.E. degree. During the summer of 1913 he
worked for The Bell Telephone Company of
Pennsylvania on a field survey of plant equipment
which included a study of property rights. Fol-
lowing his graduation he joined the student
course of the Western Electric Company at Haw-
thorne and after his shop training gained his in-
stallation experience at Philadelphia, and at
Wilmington where he worked on the first call-
distributing central office. He then came to the
Physical Laboratory at West Street and late in
1915 transferred to the Research Department
where he engaged in the development of vacuum
tubes, working with the tubes made for the
Arlington transatlantic tests.

The next year Mr. Graham joined the Trans-
mission Department but when the World War
broke out he was sent to Boston to work on the
cable system for detecting submarines, par-
ticularly on balancing problems. Towards the
end of 1917 he returned to West Street to aid in
the production of vacuum tubes for the govern-
ment. Following the war he joined the acoustical
research group where, until 1929, he was con-
cerned with the development of audiphones,

audiometers and hearing aids and with general
research in hearing. From 1929 to 1937 he was
with Electrical Research Products, Incorporated,
on general transmission and engineering of
studio recording and theater reproducing equip-
ment for sound pictures. Since his return to the
Laboratories in November, 1937, he has been
engaged in field studies to determine the optimum
transmission requirements for operators’ tele-
phone sets and associated circuits.

R. A. Mitter conferred with engineers of the
Yankee Network at Boston on June 8 on ampli-
fier systems for radio broadcasting.

T. H. Crastree visited the Pittsburgh Coal
Company at Pittsburgh on June 1 in connection
with field studies of the 10A magnetic telephone
in mine telephone systems.

H. C. Rusty visited the plant of the Art Metal
Construction Company at Jamestown, New
York, on projects involving metal furniture.

A. C. WaLKER visited the National Bureau
of Standards in Washington in connection with
textile drying research.

E. B. WHEELER discussed lamp problems at
the Nela Park Laboratories of the General Elec-
tric Company, Cleveland. He also visited Haw-
thorne on matters pertaining to lamp problems.

D. A. Quartes, with D. M. Taggart of the
Western Electric Company, visited telephone
administrations and various manufacturing plants
in England, Belgium, Holland, Denmark,
Sweden, Germany and France, studying outside
plant designs with particular attention to cables
and cable manufacture.

W. S. Hayrorp and C. SHAFER, JR., visited the
New England and Southern New England Tele-
phone Companies in connection with the intro-
duction of improved joints in outside distributing
wires and station wiring.

J. B. Dixon, with representatives of the Long
Lines Department, studied the corrosion of line
wire on the Petersburg-Georgetown line near
Covington, Virginia.

R. J. Kent, at the Bond Electric Company in
New Haven on May 22, discussed design features
of flashlights.

C. H. Amapon, in Toronto, discussed methods
of pole-line inspection and maintenance. Later
he went to Denver to conduct experiments on
the full-length creosoting of lodgepole pine poles.
He also inspected some of the first creosoted
poles of this type that have been in service in the
territories of the Northwestern and Mountain
States Companies.

G. Q. Lumspen, with Messrs. Walseth and
Stratton of the Chesapeake and Potomac Tele-
phone Company, examined experimental salt-
treated southern-pine poles on a recent trip to
the Norfolk, Virginia, area.

J. G. SEGELKEN attended the meeting of the
Transmission and _ Distribution Committee of
the Edison Electric Institute at Chica

Madison, Wisconsin, to discuss methods of
measuring the electrical resistance of poles,
W. H. S. Youry recently conferred with repre-
sentatives of the Food and Drug Administration
in Washington on the labeling and packaging of
first aid and central-office emergency supplies

A. H. Hearn, at Montreal and Ottawa, i.
served the effect of various types of creosote treat.
ments on the surface condition of red pine poles

C. D. Hocker and R. H. Cottey, with repre
sentatives of The Bell Telephone Company of
Pennsylvania and the Philadelphia Electric
Company, inspected certain salt-treated poles in
Philadelphia.

R. L. Jones and H. A. FReperick visited the
United Shoe Machinery Corporation at Beverly
Massachusetts.

B. B. Grace of the International Standard
Telephone and Cables, Limited, London, visited
the Laboratories to discuss station apparatus.

L. Devaux of Le Materiel Telephonique,
Paris, discussed station and other apparatus
while visiting the Laboratories.

At Greenwicx, Connecticut, C. H. Greenall,
G. H. Downes and P. T. Higgins observed step-
by-step wipers and banks under field-test con-
ditions. Mr. Higgins also visited the telephone
office at Roanoke, Virginia, to study main-
tenance problems on step-by-step banks.

C. H. GrEENALL attended a meeting of the
Metallurgical Advisory Committee of the Na-
tional Bureau of Standards held at Washington.

SWITCHBOARD PLUGS were investigated by
T. S. Huxham, P. Neill, R. G. Ramsdell and
M. Fritts in a Jersey City central office.

On May 5, W. Fondiller, A. R. Kemp, H. H.
Glenn, D. R. Brobst and C. S. Fuller, together
with G. R. Brown, W. S. McGill, J. S. Little and
T. G. Stover of the Western Electric Company,
discussed insulating materials with engineers of
the du Pont Company in Wilmington.

AMONG MEMBERS of the Laboratories who have
recently made trips to the Hawthorne plant of
the Western Electric Company were H. A.
Frederick, H. O. Siegmund, J. R. Townsend and
J. J. Kuhn on the development of new materials
and apparatus; B. O. Templeton, on manufac-
turing problems of coin collectors; N. R. Stryker,
acoustical testing equipment for the combined
telephone sets; W. G. Laskey, tool design for
electric meters; R. Burns, handset molding prob-
lems; D. H. Gleason and C. R. Moore, new dial
developments; J. E. Shafer, the manufacture of
an improved relay; A. F. Bennett, W. L. Tuffnell
and D. T. Eighmey, handset and instrument
problems; and H. W. Heimbach, problems that

MEMBERS OF THE LABORA-
who presented papers
at the annual meeting of the
Acoustical Society of Amer-
ica, held in New York on
May 15 and 16, were Harvey
Fletcher who spoke on Audi-
tory Patterns, Homer Dudley,
Remaking Speech, and R. N.
Marshall and W. R. Harry,
New Microphone Providing
Uniform Directivity Over an
Extended Frequency Range.

J. A. Becker spoke on
Electron Microscopes and
Some of Their Uses at the
final meeting of the Radio
Colloquium, held at the
Holmdel laboratory. He dis-
cussed various forms of electron microscopes and
their use in varied fields and demonstrated a
simple microscope with a magnification of about
300,000. At this meeting the following officers
were elected for the 1939-1940 year: A. E. Bowen,
president, A. E. Kerwien, secretary, and J. P.
Schafer, chairman of the program committee.

Ar THE Partin, New Jersey, plant of the
du Pont Company, B. L. Clarke, H. G. Arlt
and C. C. Hipkins discussed finishes.

J. G. Cuarree presented a paper, The Appli-
cation of Negative Feedback to Frequency-Modu-
lation Systems, at the May 3 meeting of the
New York Section of the I.R.E.

A. J. AHEARN presented a paper, Electron
Microscopes and Some of Their Uses, before the
Alpha Chapter of Epsilon Chi at Columbia.

Francis WiLtiaMs, for many years a watch-
man at the Section K entrance on Bank Street,
died on May 27. Mr. Williams was born in
Ireland and came to this country in 1909. He
joined the Western Electric Company on
October 7, 1919, as a night cleaner and night
watchman. In 1929 he was transferred to the
day shift where he had since been a uniformed
watchman assigned to building entrances.

ApotpH BREGARTNER, a technical assistant
in the Central Office Switching Development
Department with over forty-one years of service
in the Bell System, died on June 4. Mr. Bre-
gartner joined the Western Electric Company
in New York in 1898, and after a few months in
the machine shop, entered the group handling
the assembly and adjustment of relays. Later he
worked on special apparatus, such as the early
equipment for train dispatching, and then be-

came associated with the development of semi-
mechanical central office apparatus. For nearly
four years he took part in the early installations
of this equipment in Newark. Since then he had
been handling the adjustment and assembly of
relays in the Systems Circuit Laboratory.

On May 8, K. K. Darrow spoke on The Origin
of the Cosmic Rays before the student body at
Wellesley College.

V. J. AtBano and J. H. Gray visited Pitts-
burgh to discuss with engineers of The Bell
Telephone Company of Pennsylvania various
methods of duct sealing and to inspect duct-
sealing materials.

R. M. Burns spoke on The Tarnishing of
Metals at the meeting of the Metallurgy Collo-
quium held at M.LT.

H. W. Hermance and T. F. Ecan visited
Pittsburgh, Cincinnati, Cleveland, Detroit and
St. Louis where they made chemical studies of
conditions affecting performance of contacts of
panel bank terminals. A portable chemical lab-
oratory was used in these studies and a photo-
micrographic record was made of the terminals.

R. L. Lunsrorp and J. Zouter were at Atlanta
and J. G. Ferguson at Harrisburg, Cleveland
and Detroit to discuss installation problems of
the 355A community dial office.

J. H. SoLe went to the General Electric Com-
pany in Fort Wayne, Indiana, to discuss alter-
nators and control equipment. He also visited
the telephone company and the manufacturers of
diverter pole generators in Cleveland.

STUDIES OF GASOLINE and Diesel engines took
A. E. Petrie to Portland, Boston, Cleveland and
Lansing, F. F. Siebert to Baldwin, Pennsylvania,

and V. T. Callahan to Portland, Boston, Lan-
sing, Cleveland, Canton and Salem (Ohio).

L. M. Datutwore, of the International Stand-
ard Electric Company, London, is at the Lab-
oratories in connection with the engineering of
cable-carrier installations in Finland and Sweden.

A. G. Lane spent several days at Cleveland in
connection with the initial installation of the
3B toll switchboard.

H. D. Canttu was in Albany testing circuits
modified to meet new requirements.

W. H. ScuEeER spent several weeks at Jones-
ville, New York, testing the first installation of
the 380A unattended crossbar dial office.

T. L. Dimonp was at Batavia, Ohio, for a week
making tests on the first installation of the 355
step-by-step community-dial office.

R. W. Harper, at Cincinnati, inspected the
installation of 355A dial-office equipment.

At Cuicaco, W. J. Lacerte, C. V. Taplin and
E. L. Getz spent several days discussing with
engineers of the Illinois Bell Telephone Company
plans for making through tests on the first
crossbar offices to be installed in Chicago.

F. A. Brooks has been at Toledo in con-
nection with the field trial of a pilot-channel
deviation regulator for type-K carrier systems.

S. Rosen and J. B. Irwin were at Princeton
for tests of a line-switching circuit for the coaxial
cable between New York and Philadelphia.

A. J. AIKEns is in Winnsboro, South Carolina,
testing crosstalk in type-J systems.

L. Y. Lacy made several trips to Princeton in
connection with noise studies on coaxial cables.

R. M. Hawexortre has been in Morristown
where he took part in a coéperative inductive
coérdination study involving telephone circuits
of the New Jersey Bell Telephone Company.

J. H. SHunart and C. H. Gorman, Jr., have
gone to Eau Gallie, Florida, where they are
making open-wire crosstalk tests on type-J
carrier-system circuits.

E. S. Witcox and J. L. Linpner at Amarillo,
Texas, made J-frequency crosstalk tests on
open-wire circuits of the Fourth Transconti-
nental Line.

O. H. Coo.ipce participated in tests on a
cable being installed near Danielson, Connecti-
cut, to determine comparative results for voice-
frequency cable when installed in 750-foot
versus 1500-foot lengths.

L. C. Rosperts spent a week in Charlotte
making tests preliminary to starting a field trial
on a ground-potential compensator circuit.
H. W. Reikel of the Long Lines Engineering
Department accompanied Mr. Roberts.

WitH THE compLeETIon of high-frequency
transmission tests on open-wire lines at Mount

H. S. Winsicter and J. C. Lozier were in
Reading, Pennsylvania, during the week of Ma
27 in connection with tests of volcas as a aa
wire echo suppressor.

THE TRIAL of negative coefficient thermistors
on non-loaded cable circuits was observed at
Long Valley by L. G. Abraham, J. A. Becker
P. G. Edwards, and R. D. Fracassi. ;

H. A. Erueripce, Jr., and O. H.
of the Laboratories, and A. C. MircuE t of the
Long Lines Department, were at Danielson
Connecticut, on tests of combined capacitance
unbalance and capacitance deviation.

At Gens Fatus, New York, A. E. Bachelet
E. B. Mechling, and J. T. Schott tested the
efficacy of proposed means for suppressing clicks
caused in program circuits by operation of relays
in the office, particularly those in transmission
regulating equipment.

On May 19, L. E. Coon made a tour of the
Deal and Holmdel Radio Stations and discussed
plant equipment and procedures from the stand-
point of safety engineering and health.

A. R. THompson has been elected a director of
the American Institute of Graphic Arts, for a
term of three years. Mr. Thompson is chairman
of the Institute’s Textbook Clinic, a group of
some two hundred publishers, authors, de-
signers, and printers organized to study the
design and manufacture of educational books.

Durinc May, E. W. Adams visited the Haw-
thorne plant with T. Brooke Price, F. T. Wood-
ward, R. R. Adams and E. J. Driscoll of the
Western Electric Company and J. R. C. Palmer
of Electrical Research Products, Incorporated.

Tue LaBoraToRIEs were represented in inter-
ference proceedings by S. B. Kent attending the
taking of testimony in Camden, New Jersey;
by R. J. Guenther at a hearing before the Board
of Appeals; and by H. S. Wertz at a hearing
before the Primary Examiner at the Patent
Office in Washington.

SINGAPORE came within reach of Bell and Bell-
connecting telephones on June 1 when radio
telephone service was extended to Malaya. The
new service is provided by means of two short-
wave radio circuits—one 9,100-mile channel
between San Francisco and Bandoeng in Java,
over which service is maintained with the
Netherlands Indies, and another, 720 miles long,
which reaches from Bandoeng to Kuala Lumpur
in the Federated Malay States. Wire lines extend
from Kuala Lumpur to the Straits Settlement,
of which Singapore is the capital, and to most of
the Malay Peninsula.

N the early manual systems, all
ringing was under the control of
an operator. She would operate a
key to start it, and restore the key
to stop it. Manual ringing has long
been replaced by machine ringing on
all but small, light-traffic boards.
With this system the operator starts
the ringing, as before, but it is cut
off automatically when the  sub-
scriber answers by a “tripping” relay.
The ringing current passes through its
winding, but the relay must not oper-
ate on it under even the most unfavor-
able conditions, such as a very short
line and two ringers bridged across it.
When the subscriber answers, how-
ever, the relay must operate to stop
the ringing, again under the most un-
favorable conditions of a line that is
extremely long.

A ringing circuit is shown in simpli-
fied form in Figure 1. Under ringing
conditions, relay A is operated and
ringing current passes through the
winding of the tripping relay, a front
contact on relay a, the “ring” side of

When the receiver is lifted from the
hook, the condenser and ringer are
practically short-circuited by the
transmitter, and the lower impedance
resulting should allow enough current
to pass to operate the tripping relay.
With a maximum loop resistance of
750 ohms, including the station re-
sistance, however, and some 250 ohms
in the relay winding and the rest of
the circuit, the current is only about
100 milliamperes, which as noted

above is the value at which it should
not operate. To insure satisfactory
tripping, therefore, two things are
done. One consists in putting a bat-
tery in series with the ringing ma-
chine; and the other, in making the
tripping relay more sensitive to di-
rect than to alternating current. This
does not affect the ringing, since the
d-c component is blocked by the con-
denser, but it increases the current
that flows when the call is answered,
since the path through the trans-
mitter has no condenser in series.
Ringing is supplied through an
interrupter that gives a short interval
of ringing followed by a longer inter-

val of silence. To make it possible for
the tripping relay to operate during
the silent as well as during the ringing
interval, battery is also connected
during this silent interval. A simpli-
fied schematic diagram of the ar-
rangement is shown in Figure
2. To make the tripping relay
less sensitive to alternating
than to direct current, a cop-
per sleeve is placed over the
core. With alternating current
in the winding, an opposing
current is induced in this
sleeve, so that the net effect of
the current is less, while with
direct current in the winding,
the sleeve has little effect. As a

result, the relay is from three to five
times more sensitive to direct current
than it is to alternating. The lowest
operate current—or a 750-ohm ex.
ternal circuit loop during the silent
interval—is about 50 milliamperes d-c;
the highest non-operate current—for
a minimum length of loop and two
parallel ringers—is some 100 milli-
amperes a-c. Since the relay is at least
three times more sensitive to d-c than
to a-c, however, it can readily be made
to operate on 50 milliamperes d-c and
not to operate on 100 milliamperes a-c.

In recent years there has been a
trend toward the use of smaller con-
ductors in cables, with the result that
the resistance of subscriber loops has
tended to increase. Because of this
tendency, the new crossbar system
has been designed to give service over
1500-ohm external circuit loops. As
part of the crossbar development,
therefore, it has been necessary to
provide a tripping system for this in-
creased range. With a 1500-ohm loop,
the operate current under the most
unfavorable conditions will be only
about 25 milliamperes. The former
relay, if adjusted to operate on this
very small current, would have un-
stable contact, and so it was necessary
to redesign its structure to provide the
necessary contact stability at 25
milliamperes. Since this requires that
the relay be more sensitive to direct

current, something
also had to be done to
make it less sensitive
to alternating current.

This was accom-
plished by a design
modification due to H.
N. Wagar. Its major
features are shown in
comparison with those
of the former relay in
Figure 3. Both relays
are alike in having a
central core on which
the winding is placed,
a cylindrical iron shell
surrounding the wind-
ing, and a circular armature that
bridges the annular space between the
core and the outer shell. In the earlier
form a copper sleeve was placed over

In the new relay, known as the
114KA, the sensitivity is increased by
an enlarged pole piece at the end of

Fig. 4—The 114KA tripping relay with armature removed
to show the copper ring around the pole piece

the core nearest the armature. This
larger area reduces the reluctance of
the air gap, and thus permits a larger
flux to flow for the same magnetizing
force. This larger flux, in turn, results
in a greater pull. To prevent this in-
creased sensitivity from being effec-
tive on alternating current, a large
copper ring is placed adjacent to the
added pole piece to allow a larger
opposing current to flow. This added
copper ring is evident in Figure 4.

This modified construction has not
changed the general appearance of the
relay, so that the new relay—shown
in the photograph at the head of this
article—looks like the former one
except for a few minor changes in
spring and contact arrangement. A
front contact has been provided in
addition to the back contact, but it
is used in only a few cases. With this
new relay, the ratio of a-c to d-c cur-
rent necessary to operate is from
seven to fifteen—a substantial in-
crease over the former ratio.

S has been explained in a pre-
vious article, the functions of
terminating markers are in

general similar to those of originating
markers. The differences arise chiefly
from the difference in type of circuits
which they control. While the origi-
nating markers must find an idle
trunk out of several hundred groups of
trunks, the terminating marker must
be able to find one particular line out
of a possible ten thousand. It must
first test this line for busy, and, if the
line is found idle, must then establish
a connection to the crossbar switch to
which that line is run, so that it may
find an idle path to it from the in-
coming trunk, and in this manner
establish the talking connection.

ever, may be that of a private branch
exchange, instead of an individual or
party line. In such a case it is not
sufficient to test only one line; since
there will a group of trunks to the
PBX, the marker’s task is to select the
first one in the group that is idle. One
of the fundamental features of the
crossbar system is to test a group of
paths and trunks simultaneously so as
to reduce the holding time of the
markers to a minimum. To carry out
this principle, the terminating marker
is arranged to test twenty lines at a
time where the number called is that
of a PBX; while when it is that of
an individual line, only the desired
line will be tested, although the entire
group of twenty consecutively num-
bered lines, including the desired one,
will be brought to the marker.

The possible 10,000 subscriber num-
bers of the office are therefore ar-
ranged in blocks of twenty, and a
block relay is provided for each such
group. In function the block relays
are similar to the route relays of the
originating marker, but they are con-
trolled and operated in a different
manner. The route relays are part of
the originating marker, and one or
more for each office code is provided in
each marker. The block relays, on the
other hand, are not part of the termi-
nating marker, and there is only one
for each group of twenty subscriber
numbers in the office. They are multi-
contact relays assembled ten in a row,

and four such rows are mounted on
the upper part of a frame as shown in
the photograph at the head of this
article. When operated, each block
relay closes sixty contacts, three for
each of twenty line numbers. Twenty
of these, one for each line, are in the
leads used for the busy test. There
may be as many as 500 of these relays
in an office, and, to simplify the selec-
tion of the desired one, they are
grouped into sets of five, and operated
through hundred-block relays. Each
of the latter has five contacts, one for
the winding of each of the twenty-
block relays in that hundred-block.
These hundred-block relays
are mounted under one of the
long cans that are mounted
above the four rows of twenty-
block relays.

Several of the hundred-block
relays are formed into a “‘num-
ber group” and by means of a
number-group connector can
be temporarily connected to
any one of the terminating
markers in the office. The
number-group connector re-
lays are of the same type as
the twenty-block relays, and
are also assembled in rows of
ten, eight rows being mounted
on a frame as shown in Figure
1. Four of these relays, oper-
ated simultaneously, are re-
quired to connect a number
group to one marker—the four
being mounted one above the
other. Since each number
group must have access to all
of the terminating markers, of
which there may be as many
as ten, ten sets of four relays
may be furnished for each
number group. Each frame of
Figure 1 has connector relays Fi
for two number groups, the

This division of lines into number
groups permits a number of markers
to be locating lines at the same time.
If two markers should receive calls
for numbers in the same number
group at the same time, one marker
must wait for the other to set up its
connection. This delay is ordinarily a
small fraction of a second. To pre-
vent unreasonable delays, however,
the hundred-blocks formed into a
number group usually represent only
about one thousand terminating calls
during the busy hour. For simplicity

'g.. 1—Number-group connector frames in the
Murray Hill-6 Office on East Thirtieth Street

When a marker is seized by a
sender, it must determine—from the
number that has been dialed—the

Fig. 2—Synoptic diagram of the decoding
features of the terminating marker and
number-group circuit

correct number-group connector to
operate, and also the correct hundred-
block and _ twenty-block relays to
operate in this number group. This
process is known as decoding, because

Fig. 3—Combinations of operated register
relays to give the various digits

the decimal directory number it re-
ceived, 2845 to take a concrete ex-
ample, must be translated or decoded
into terms designating a number-
group, a hundred-block relay, and a
twenty-block relay.

A synoptic diagram of the circuits
involved in this part of the marker’s
work is shown in Figure 2, where
reference is made to two following
illustrations giving sections of the
circuit in greater detail. As a basis for
its action, the marker has recorded
on four groups of register relays the
number that has been dialed by the
subscriber. The proper register relays
in each group were operated by the
terminating sender when the marker
was seized, as described in the pre-
vious article. These relays are similar
in arrangement and function to those
of the originating markers used for re-
cording the office code, except that
four sets of relays are required instead
of three because the subscriber num-
ber consists of four numerals. The re-

lays of the group for the first, or
thousands digit, also differ in being
numbered 1, 2, 4, and 8, instead of
1, 2, 4, and 5, as are the other groups
in the terminating marker and all the
groups in the originating marker. The
combinations of the relays within a
group to give the various digits are

Since a number group
is made up of hundred-
blocks, a determination
of the hundred-block in-
dicated by the registered
number is sufficient to
designate the number
group desired. This hun-
dred-block designation
will also, of course, indi-
cate which hundred-block
relay in the number group
to operate. The marker
is designed to determine
the hundred-block by
first picking a group of
s00 numbers — or five-
hundred group — and
then narrowing its selec-
tion to one of the five,
although the two opera-
tions are carried out si-
multaneously, not suc-
cessively. Due to the
fact that there are twenty
groups of 500 sub-
scriber numbers in a
10,000 number office,
the marker is equipped
with twenty 500-group
relays, one for each of
the twenty groups of
five hundred numbers.
It also has five hun-
dred-block relays, one
for each of the hun-
dred-blocks in a 500-
group, and leads from
contacts of hundred-

block relays are multipled to a set of
corresponding contacts in each five-
hundred group relay. The arrange-
ment is shown in greater detail in
Figure 4. These hundred-block relays
in the marker should not be confused
with those in the number-groups.
The latter are individual to a set of

Fig. 5—Register relays in the crossbar system operated for
the various five-hundred groups

100 directory numbers, while those in
the markers merely designate the five
sets of 100 numbers into which any
group of 500 may be divided.

The five-hundred group relay to be
operated is determined from the
thousands-group and the No. 5 relay
of the hundreds-group of the register
relays, as shown in Figure 5. From this

table it will be noted
that the number of the
s00-group relay is de-
termined by the thou-
sands digit of the num-
ber dialed, but since
there are two 500-
groups in each thou-
sand numbers, there
are two $00-group re-
lays for each of the ten
“thousand” digits from
© to 9, the number for

one group being primed
to make the distinc.
tion. In each case, the
primed relay is for the
500-group whose hun-
dreds digit is § of
greater. For number
2845, for example, the
No. 2’ FH relay will be
operated, the 2 indicat-
ing that the thousands
digitis2,and the prime,
that the hundreds digit
is five or above.
Which hundred-
block relay is operated
depends on the first
three relays of the
hundreds register re-
lays as shown in Fig-
ure 6. It will be noticed
that each combination
of the H relays corre-
sponds to two hun-
dred-blocks, one below
and one above 500. For

the number 2845, the No. 3 HB relay
would be operated, in conjunction with
the No. 2’ rx relay. This determines
the number as between 2800 and 2899,
but had the same uB relay been oper-
ated in conjunction with the No. 2 Fx
relay, the number would have been
between 2300 and 2399. In this way a
single set of five HB relays, in conjunc-

Fig. 6—Register relays that are operated for the various
hundred-block groups

tion with twenty FH relays,
can be made to designate any
hundred-block in the office.

The operation of one HB and
one FH relay in the marker
closes paths to two sets of
terminal strips—one marked
st, and the other us. These
terminal strips form part of
one of the marker bays as
shown in Figure 7. Since there
are twenty FH relays, each
carrying a pair of contacts for
each of the five HB relays,
there are one hundred termi-
nals in each of the two termi-
nal sets, one corresponding to
each possible hundred-block
in the office. Adjacent to the
one hundred st terminals is
a group of terminal strips,
each strip representing a num-
ber group. Each of the one
hundred st terminals is cross-
connected to the strip repre-
senting the number group con-
taining that hundred-block of
subscriber numbers, and clo-
sure of this path in the marker
will cause the number group
to be connected to the marker.
Adjacent to the one hundred
HB terminals is a similar group
of terminal strips, each strip
representing one of the hundred-blocks
of subscriber numbers in the selected
number group. Each of the one
hundred HB terminals is cross-con-
nected to the strip which will oper-
ate the hundred-block relay in the
selected number group that gives ac-
cess to the corresponding hundred
subscriber numbers.

So far, a particular number-group
connector has been selected, and a
hundred-block relay in that group
has been operated. Which particular
twenty-block relay is operated is de-

Fig. 7—Each terminating marker consists of two
bays, one consisting chiefly of three cabinets of relays,
and the other of one relay cabinet and the cross-

termined by the combinations of
operated relays of the tens-group of
register relays in the marker. Five
leads are carried from this set of
register relays through the number-
group connector to the number group,
where they are multipled to the five
contacts of all the HB relays as-
sembled in that number group, as
shown in Figure 8. From this relay
they run to the windings of the
twenty-block relays—the contacts of
each hundred-block relay being con-
nected to the five twenty-block relays

it controls. The circuits through the
tens register relays are so arranged
that when no relay or the No. 1 relay
is operated, ground will be placed on
the lead that runs to the first twenty-
block relay—indicating that the last
two digits are between 00-19, and
when the No. 2 relay, or the No. 1
and No. 2 relays, are operated,

By this decoding process, a par.
ticular block relay has been operated,
and three contacts have been closed
for each number of the block that in.
cludes the one called. One of these
contacts for each line will be used for a
busy test, and the other two will be

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N large central offices a variety of
tone signals are required to expe-
dite the operating procedure, and
these as well as ringing current are
supplied by motor-generator sets as
already described.* For private branch
exchanges and for the smaller central
offices ringing and tone supply are
also required, but the load is much
lighter so that the large motor-
generators are not economical to use.
To meet the requirements of these
smaller offices a number of types of
equipment have been employed, de-
pending on the size and requirements
of the office, and for the most part
have given excellent service. None of
them, however, have sufficient tone
and interrupter equipment for some
of the new community dial offices;
and for the most part they permit a
greater variation in output voltages
than is desir-
able for some
applications. A
new small ring-
ing machine
thus seemed
necessary.
What was
desired was an
assortment of
tone and inter-
rupter circuits
comparable to
that of the
larger motor-
generator sets

but without the large size and cost of
the more extensive installations. To
meet this need, the KS-5510 ringing
machine, shown in Figure 1, was de-
veloped. Instead of being a motor-
generator as the larger sets are, it is a
rotary converter like the gp design,
one of the smaller machines. A rotary
converter combines a d-c motor and
an a-c generator in the same unit,
having a common set of field coils
and a single armature, with a com-
mutator on the motor end and slip
rings on the generator end. The con-
verter runs on current from the office
battery, and 20-cycle a-c is taken
from the slip rings, through a step-up
transformer, for the ringing supply.

On a shaft extension at the commu-
tator end are four rings for supplying
the high and low tones,* from which
~ *REcorD, April, 1931, p. 385.

the various tone signals are derived
by interrupting the continuous tones
at various rates. Each basic tone is
produced by a slip ring and a seg-
mented ring with its alternate seg-
ments connected to the slip ring. The
number and width of the segments are
proportioned so that battery current
passing in through the slip ring is

the advantage of being a smaller ang
less expensive machine than a motor.
generator, speed regulation with jt
becomes more difficult. With a motor.
generator set, there are two separate
machines, each with its own field, and
an adjustment of the field of the
motor—made to hold a constant
speed—has no effect on the voltage

interrupted at the proper rate. The
changes in current are converted by
means of repeating coils into alter-
nating voltages or tones having fre-
quencies equal to the revolutions per
second of the machine times the num-
ber of interrupting segments in each
ring. Beyond the tone rings is the
centrifugal speed regulator, which
maintains the speed of the set within
the required limits.

At the other end of the converter,
beyond the main slip rings, is a worm
driving a gear on a counter shaft,
which rotates at 10 rpm. This is the
interrupter shaft. It is arranged to
mount as many as six disks, each
drilled around its periphery to take on
each side one or more pins with
sleeves over them to act as rollers.
Each such disk has a set of contact
springs that the pins raise and lower
as the shaft rotates, and each set of
springs acts as an interrupter for
ringing current or for one type of
tone. As many are mounted as needed
up to a maximum of twelve.

20-CYCLE
output sistance in the motor field cir.
cuit. As the motor slows down,
-- the period of short circuit is re-

duced and that of open circuit
increased, so that there is a
net decrease in average field
current and a corresponding
increase in the speed of the motor.
A simplified schematic of such a set
is shown in Figure 2.

With a rotary converter, however,
the same field serves for both motor
and generator, and if the field current
is decreased to offset a falling speed,
the generated voltage will decrease.
To avoid this, a resistance is inserted
in the armature circuit, as shown in
Figure 3, and the regulator contact is
allowed to short circuit this resistance
for longer or shorter periods as the
motor slows down or speeds up. Both
speed and voltage vary directly with
the voltage across the armature, and
thus increase as the armature resist-
ance is shorted out for longer inter-
vals. A series field is also used with

A modified form of this machine,
called the KS-5546 code-ringing ma-
chine, is arranged to give the code
ringing commonly used on rural lines.
Since as many as twenty parties may
be connected on such a line more
interrupter springs are required. For
this reason the interrupter shaft is
made long enough to accommodate
eighteen spring pile-ups, eleven of
which are used to furnish the codes
alone. Since cost is particularly im-
portant in these small offices, the

speed regulator has been omitted.
This results in wider voltage varia-
tions in the ringing output, and the
rating of the machine has been slightly
decreased, which is permissible be-
cause of the light load under which
these offices operate. For the same
reasons it has been possible to use
smaller brushes on the tone rings, and
thus make another small saving. As a
result of the accumulated savings
this code-ringing machine will give a
greater variety of signaling interrup-
tions than the KS-5510 machine, and
at the same time will cost less.

Modern business management should be, and I believe
for the most part 1s, imbued with an interest in the public
welfare. It provides the basis of satisfaction to educated
men, for industry is the basis of the well-being of the
nation and commerce the chief hope of an economy in
which the nations of the world can live in peace. Business
is not a simple calling. It requires skill of a high order,
capacity and a sense of responsibility. Business today is
not based on the conception of a world of a limited amount
of goods in which, if one man gets more, another man must
get less. Its objective, whether conscious or not, is to create
more for all. And in doing so it must reconcile the interests
of the workers, the owners and the consumers. Especially
today it must carry on with sympathetic understanding of
the necessary restrictions to its complete freedom that
grow out of what is called the “public interest’’—the
interest of the general public, whether or not workers,
owners or customers of the particular industry.

—From an address by Walter §. Gifford at the Commence-
ment Exercises of Union College, Fune 12, 1939.

Increased power and better quality of
reception is provided for police cars and
other mobile units by the new Western
Electric 228A radio telephone equipment.
Its major units are a short-wave receiver
and 15-watt transmitter, each with its
own high-voltage power supply operated
from the car battery. In addition, a small
control unit, a loudspeaker, and a tele-
phone handset are mounted in front of the
driver. Besides its threefold increase in
power, this new Laboratories apparatus
includes a greatly improved codan to dis-
able the receiver when no signal is being
received, anda device to reduce noise peaks.

J. W. Dexn joined the Engineering
Department of the Western Electric
Company in the fall of 1919, and at first
engaged in laboratory testing and analy-
sis of manual and panel telephone cir-
cuits. Subsequently he worked on the
design of manual circuits and later of
automatic testing circuits for panel
offices. Since 1933 he has been engaged in
the design of automatic testing circuits
and marker circuits for the crossbar sys-
tem. During this period,
he has attended classes
at the Polytechnic Insti-
tute of Brooklyn from
which he received the de-
gree of Electrical Engi-
neer in 1932.

J. W. Fotey graduated
from the University of
Illinois in Ig91I, receiving
the degree of B.S. in Elec-
trical Engineering, and
immediately joined the
Western Electric Com-
pany at Hawthorne. Upon
the completion of the
student course, he entered

the Transmission Laboratory at New
York, where he was concerned with
general transmission studies. His work
soon became centered upon telephone
sets and their associated circuits. He has
been intimately associated with the de-
velopment of the anti-sidetone telephone
sets now standard for both subscribers
and operators as well as many sets for
special purposes such as train dispatch-
ing, amplifier sets for the hard of hearing,
and loudspeaker systems
for both intercommunicat-
ing and regular tele-
phones. More recently he
has participated in the
development of closed-
core induction coils for
operator and subscriber
sets, of acoustic shock pre-
vention devices, and in
further studies for the im-
provement of subscriber
telephone sets and their
associated apparatus.

Two years prior to his graduation, he had
joined the Technical Staff of the Lab-
oratories, and until 1928 was associated
with the Research Department in con-
nection with the development of terminal
equipment for high-speed submarine
cables. At the completion of this work he
transferred to the Apparatus Develop-
ment Department where he has been en-
gaged in the development of precise im-
pedance-measuring equipment.

H. B. Briccs received the B.A. and
M.A. degrees from the University of
Wisconsin in 1919 and 1921, and the
Ph.D. degree in Physics from the Uni-
versity of Chicago in 1925. His under-
graduate work was interrupted by two
years spent in France as a Lieutenant of
Infantry. From 1921 to 1923, and again
from 1925 to the time he joined the
Laboratories in 1929, he was a member of
the teaching staff at the State College of
Washington. Until the past year and a
half he has carried on fundamental re-
search in the fields of photoelectricity and
the optical constants of metals. At pres-
ent he is working on electron optical
problems associated with television.

R. D. pe Kay was graduated from the
United States Naval Academy in 1918.
He served in the war as engineer officer on
destroyers, and after the war as com-
manding officer. In 1922 he left the Navy
and joined the power development group

of the Laboratories, where he supervises _
rectifier and machine development.

L. J. Sracy received the A.B. degree
from St. Lawrence University in 1go9.
After six years of school teaching, he
entered the University of Chicago for
two years of graduate study in physics
and mathematics. In the radio division of
the Signal Corps in 1918 he rose to a
second lieutenancy, then returned to
Chicago to receive the Ph.D. degree in
1919, and later that year entered the
Systems Development Department of
these Laboratories. He has been con-
cerned with ringing and tone studies and
other special technical problems in the
local central office laboratory, and later
was placed in charge of a group devoted
to this work. Since early in 1937 he has
also been in charge of the step-by-step
and manual testing groups.

Bell Laboratories Record 1939-07: Vol 17 Iss 11