transoceanic telephony in 1928
and 1929, attention was directed by
Bell Telephone Laboratories toward
determining the properties and use-
fulness of ultra-short waves. The
short-wave transoceanic circuits are
operated at frequencies between 5
and 21 megacycles while the ultra-
short waves are at frequencies above
30 megacycles, which is generally
taken as the upper limit of the short
wave range. It had previously been
discovered that these higher frequen-
cies were not in general reflected from
the Kennelly-Heaviside layer. They
were, therefore, considered primarily

cation, where the waves followed es-
sentially an optical or straight-line
path from the transmitter to the re-
ceiver. In the telephone plant there
are instances where natural barriers
so separate points only a short dis-
tance apart that it is difficult and ex-
pensive to construct ordinary tele-
phone lines or submarine cables to
connect them. It seemed that for
such conditions ultra-short wave radio
extensions might be a satisfactory
means of giving telephone communi-
cation. To be economically feasible,
however, such radio circuits must be
inexpensive both in first cost and in
operation.

During the last few years, the Lab-
oratories have been experimenting
with an ultra-short wave circuit be-
tween Deal and Holmdel, New Jersey,
with the thought of developing equip-
ment capable of unattended operation.
Some time ago this development
reached the stage where it seemed de-
sirable to carry out a trial of a two-
way circuit under conditions approx-
imating commercial use to gain ex-
perience with the problems involved
in regular operation. In particular,
it was desired to design and install the
radio stations for operation without
direct attendance, so that the appara-
tus could be located remotely from a
central! office.

After a study of possible locations,
it was decided in cooperation with the
New England Telephone and Tele-
graph Company to carry out the trial
installation across Cape Cod Bay, be-
tween Green Harbor and Province-
town, Mass. The coastal station of
the New England Telephone and Tele-
graph Company, already existing at
Green Harbor, made a convenient
place in which to install one end of the
system. The physical conditions are
also favorable for an ultra-short wave

link between that point and Province-
town, 25 miles away. The sand dunes
near Provincetown, rising about 100
feet in height, make it possible to
secure an optical path across the bay.
Furthermore, Provincetown is fairly
accessible by motor car around the
Cape and is already provided with
wire circuits, so that the radio link
need not be completely depended
upon. This location is thus a good
proving ground for this new type of
telephone circuit.

Accordingly, the radio link has been
established across the bay, as indicated
on the map, and extended at Green
Harbor by wire to Boston, to form
a direct Boston-Provincetown toll
circuit. At Boston and at Province-
town the circuit appears at a jack
in the switchboard alongside the jacks
of other toll circuits. The insertion of
a cord into the jack starts the radio
transmitter at that end of the radio
link. The receivers at both ends are
kept in constant operation while the
circuit is available for trafic. Ringing
is accomplished by sending a 1000
cycle tone interrupted at twenty
cycles over the radio circuit. Since
the radio transmitter requires less

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STAGE RECTIFIERS
AUDIO
AMPLIFIER
RELAY TO MAKE
STAGE OSCILLATE
AT 1500 CYCLES
FOR TEST
Fig. 1—Block schematic of ultra-short-wave transmitter
October 1934 35

than one second to start, the operator
may ring immediately after inserting
the cord. Privacy equipment, similar
to that used on the transatlantic short
wave channels, is installed.

The receiver is started and stopped
by the operation of a key at the local
test board. The power supply is
arranged so that when the receiver is
in operation, current is also applied
to some of the filaments of the trans-
mitter. Provision is also made for
testing the overall operation of the
transmitter and receiver at each end
from the local test board. A tone is
generated which modulates the trans-
mitter, and if both transmitter and
receiver are operating properly, a side-
tone will be produced in the local
receiver which can be heard by the
test board operator.

The transmitter, developed by R.
W. Friis and L. M. Klenk under the
supervision of N. F. Schlaack, is
crystal controlled, and is capable of
delivering 15 watts of carrier power
which can be completely modulated.
A block schematic for the Green Har-
bor transmitter is shown in Figure 1.
The Provincetown transmitter is the
same except that the output frequency
is 63 megacycles. A quartz crystal

oscillator is followed by two harmonic
generators, a push-pull modulating
amplifier, and a push-pull power am-
plifier. Modulation is accomplished
by supplying audio-frequency modu-
lating power to the plate and screen of
the modulating amplifier and to the
screens of the second harmonic gener-
ator and the power amplifier.

Two rectifiers employing hot-cath-
ode mercury-vapor tubes supply plate
and screen potentials for all tubes.
Grid bias potentials are obtained from
cathode resistors and grid leaks. Grid
and plate circuits of each stage are
shielded from each other to prevent
extraneous coupling and interstage
feedback. The transmitter operates
entirely on standard commercial 1 1o-
volt, 60-cycle current.

The radio receivers, developed by
G. Rodwin and C. H. Swannack under
the direction of F. A. Polkinghorn,
also operate from a 110-volt, 60-cycle
circuit, and are of the double detection
type. A block schematic is shown in
Figure 2. To make unattended opera-
tion possible, a crystal oscillator is
used as a source of beating frequency.
A single-stage harmonic generator
produces sufficient voltage of the
eighth harmonic of the crystal fre-

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Fig. 2—Block schematic of ultra-short-wave receiver
36 October 1934

Fig. 3—The ultra-short-wave transmitter is
mounted in a metal container suitable for
pole mounting

quency for satisfactory operation of
the detector. The intermediate fre-
quency amplifier consists of three
stages of amplification at 1600 kilo-
cycles, and has a band width of
approximately 50 kilocycles. A small
amount of automatic volume control
is provided to compensate for slight
variations in received voltage caused
by variation in humidity and other
factors.

The receiving and transmitting an-
tennas are identical and are mounted
on 100 foot poles fifty feet apart.
Horizontal exciter and reflector ele-

ments are supported on standard
cross-arms. Four pairs of half-wave
exciter elements, each comprising two
half-wavelength conductors, are spaced
one-half wavelength apart in a vertical
plane on one side of the pole. Re-
flector elements are similarly arranged
on the opposite side of the pole, the
spacing between exciters and reflectors
being one-quarter wavelength. The
transmitter and receiver are each
mounted in a metal container suitable
for mounting on the antenna poles at
a later date. At the present time they
are installed in a small building lo-

Sions to prevent maintenance men from com-
ing in contact with high potentials

cated between the transmitting and
receiving antennas. The mechanical
design of the transmitters and the
station layout were made by M. E.
Fultz and J. L. Mathison.

under the direction of A. A. Oswald.
The system was put into trial service
early in July. It was found to yield a
high-grade, two-way telephone cir-
cuit and is adding to our knowledge of
the practical problems and capabili-
ties of such a system.

This picture shows all that remains in evidence today at Montauk, Long Island, of the
experimental radiotelephone station which was erected there by the Bell System in 1915
and shown on page 512 of the Recorn for Fuly 1931. This was the first radiotelephone
effort of the Bell System and, indeed, was the first vacuum-tube radiotelephone trans-
mitter ever built. Its successful transmission to Wilmington and to St. Simon’s Island,
Georgia, were preliminaries to the famous experiments later that year, in which the voice
was first projected across the oceans. All that remains is this box on a stub pole. It
housed the switch which threw the antenna lead-in either to ground or to the apparatus
within a building which siood nearby

the receiver is lifted from the
hook to the instant it is returned—
magnetic forces play a very important
role. The relay which closes the lamp
circuit and thus attracts the attention
of the operator; the transformer, called
a repeating coil, through which the
speech current flows from one sub-
scriber’s circuit to another or to a
trunk; the ringer which summons the
called subscriber and the receiver it-
self which transforms the speech cur-
rents into sound waves—all depend
upon magnetic materials for their
operation. What material is the best
for each purpose has been the subject
of continuous inquiry and develop-
ment in the Laboratories.

In a very general way magnetic
materials divide into two classes:
those which can be easily magnetized
but will lose their magnetism when
subjected to small reverse magnetiz-
ing forces; and those which, although
more difficult to magnetize, retain a
large part of their magnetism even
under the action of considerable de-
magnetizing forces. The first class
comprises the so-called magnetically
soft materials used for electromagnets,
among which are magnetic iron, silicon
steel, the permalloys, cobalt iron,
perminvar and permalloy: dust. In
the second class, of magnetically hard
materials for permanent magnets, are
found low chrome steel, high chrome
steel, tungsten steel, and cobalt steel.

terial there are five properties which
serve as criteria of its quality. The
first is the ease with which it may be
magnetized, a quality known as “ per-
meability”, which is measured by the
ratio of the flux density to the mag-
netizing force which produces it. Not
only do materials differ in permea-
bility, but the same material itself has
different values of permeability under
different magnetic conditions. The
ease of magnetization, in other words,
depends upon the intensity of mag-
netization. ‘One of the permalloys,
for example, has a very high initial
permeability which increases rapidly
until a flux density of 5,000 or 6,000
gausses is reached. From this point
the permeability falls rapidly to a
flux density of about 11,000 gausses
when it becomes practically saturated.
For moderately high values of mag-
netizing force and, correspondingly,
of flux density, magnetic iron on the
other hand has a relatively high per-
meability, although for small mag-
netizing forces its permeability is only
a small fraction of that of permalloy.

Another property of importance in
a material is the continuance of the
magnetized condition when the mag-
netizing force has been removed. This
quality is measured by the residual
induction, that is, that value of flux
density remaining in a completely
closed core of the material when a
given magnetizing force is removed.
Another very important quality is
the coercive force—the magnetizing
force which must be applied in the

“ frictional resistance. This
phenomenon, known as
“hysteresis” gives rise to
the term “hysteresis loss”
which represents the ener-
gy used up in such a rear-
rangement whenever the
material undergoes _peri-

zation, as in an alternating
current transformer.
Another loss under the
same conditions arises from
the existence of eddy cur-
rents which are induced
within a magnetic core
when it is energized by an
alternating current. This
loss, like the hysteresis loss,

hence its designation “‘hysteresis loop.” Dotted lines are
for lesser degrees of magnetization

opposite direction to remove the
residual induction: that is, to de-
magnetize the material. These last
two qualities are of course most im-
portant in the selection of materials
for the production of permanent mag-
nets such as are used in polarized
relays, in telephone receivers and in
magneto-generators. The existence of
the qualities of residual induction and
coercive force means that the flux
density within the magnetized core
depends at any instant not only upon
the magnetizing force then acting, but
also upon the previous magnetic his-
tory of the core.

In attaining its successive values
the flux density lags behind a changing
magnetizing force much as if the mag-
netic elements of the core were being
rearranged against the opposition of

manifests itself by heat.
Sectionalizing the core by
laminations insulated from
one another reduces this
loss. Similarly, using a
material of a high elec-
trical resistivity means fee-
bler eddy currents and
smaller: losses. Hysteresis loss and
electrical resistivity are therefore two
qualities of importance in the design
of apparatus for alternating currents.

The fact, for example, that the
electrical resistance of magnetic iron
is relatively low, hence, that its eddy
current loss is large, practically limits
its use in the design of telephonic
equipment to cores for electromagnets
which operate on direct currents. The
fact that its coercive force is fairly
low and its permeability quite high,
even at relatively high flux densities,
indicates that it may be used for re-
lays in which the armature is attracted
when a current is sent through the
windings and falls away again under
gravity or spring pressure when the
current ceases. “Magnetic iron’ is a
term applied to the material which is

In silicon steel, which may be con-
sidered a 4% silicon alloy of magnetic
iron, the resistivity is about five times
that of magnetic iron. Eddy currents
are greatly decreased in consequence,
and the material is therefore adapted
for use in cores of apparatus operating
within the audio frequency range.
This steel also has the advantage of a
considerably higher permeability than
magnetic iron at the low flux densities
which are usually produced in tele-
phone apparatus operated by speech
currents. It is used largely in cores
of transformers, and induction and
retardation coils.

A material physically superior to
silicon steel for the cores of audio fre-
quency apparatus is ‘ 45 permalloy”.
The name “permalloy”’ covers certain
alloys of nickel and iron developed in
these Laboratories and possessing re-
markable magnetic properties. Differ-
ent combinations of these materials
are designated by the amount of
nickel which they contain. The “45
permalloy” has a resistivity nearly as
high as silicon steel and a permeability
at low or moderately high flux den-
sities two or three times greater. Its
coercive force is also considerably
lower. Its cost however is considera-
bly greater and in designing apparatus
this factor must be balanced against
its better magnetic properties. It is
used largely in transformers and cer-
tain types of relays.

The “78 permalloy” is a material
having remarkably high permeabil-
ities. Its initial and maximum per-
meabilities are more than ten times
those of silicon steel while its coercive
force is only about one-tenth. Al-
though i its hysteresis loss is very low,
its resistivity which is only about one-
third that of silicon steel makes it

less suited than some of the other .
permalloys for audio frequency appa-
ratus. It is used mainly for the cores
and armatures of sensitive relays.

To adapt permalloy for high fre-
quency use about 4% of the iron con-
tent of the 78 permalloy was replaced
by a like amount of chromium. This
gave us “3.8-78 chrome permalloy”
which has been used for general pur-
poses. This material has a resistivity
somewhat higher than 4% silicon steel
and an initial permeability about ten
times as great while its coercive force
is only about one-tenth as large. While
it is relatively expensive, it is largely
used, in audio frequency transformers
and in some carrier frequency coils.
In the form of thin tape a chromium
permalloy has been used for the con-
tinuous loading of a number of sub-
marine telegraph cables.

In distinction from the permalloys
there has been developed in the Lab-
oratories a material which, unlike the
permalloys that saturate at relatively
low flux densities, does not reach
practical saturation until the flux
density reaches about 24,000 gausses.
This is an alloy of iron and cobalt in
approximately equal proportions. To
aid in its fabrication 2% of vanadium
has been added. Its initial permea-
bility is three or four times that of
magnetic iron while its maximum per-
meability is only about one-third as
high; but above a flux density of
about 12,000 gausses, its permeability
is about four times as great as that of
magnetic iron. The high cost of this
material has greatly limited its appli-
cation, but it is finding a field in the
pole tips of electromagnets producing
highly concentrated magnetic forces.

Another development of the Lab-
oratories is ‘‘perminvar”, whose re-
markable magnetic qualities bid fair
to extend the usefulness of magnetic

materials. This name has been applied
to the alloys of iron, nickel and cobalt
which when properly heat-treated are
distinguished by their constancy of
permeability over a region of flux
density from zero to about one thou-
sand gausses. Since their permeability
is substantially constant and their
hysteresis loss small in this region,
the perminvars are superior to the
permalloys, and to the other magnetic
materials previously discussed, in re-
spect to the amount of distortion pro-
duced in transmitted speech currents.
Hence the use of coils with perminvar
cores will result in distinctly superior
transmission circuit characteristics.
This is of especial importance in
carrier systems. A perminvar which,
over the region mentioned, exhibits

great constancy in permeability, con-
tains 45% nickel, 25% cobalt, and
30% iron. When properly heat-treated
this perminvar has a permeability of
about 400; this value is sensibly con-
stant up to a flux density of 1000

gausses. Other compositions have
been found more desirable for specific
purposes. For example, the perminvar
containing 70% nickel, 7.5% cobalt,
and 22. 5% | iron and designated er
70 perminvar” has a permeability of
about 800 and its constancy is limited
by specification so that its permea-
bility increase must be less than 1%
over a range of flux density from zero
to 500 gausses. One of the greatest
drawbacks at present to the wide ex-
tension of the use of perminvar is its
permanent loss of the perminvar
characteristics if carried even mo-
mentarily to flux densities of only a
few thousand gausses. Ordinary meth-
ods of demagnetization are only par-
tially successful. Due to this char-
acteristic and its high cost it has had
application to only a few coils in which
drastic reduction of modulation effects
was demanded.

For apparatus such as the loading
coils which are inserted in long tele-
phone lines to improve transmission,
a core material is required which will
introduce very small transmission
losses and wave-form distortion. More
specifically, the hysteresis and eddy

current losses as well as the distorting
modulation effects must be small over
a wide range of magnetizing force.
To accomplish this it can be demon-
strated that the effective permeability
of the loading coil core must be kept
low relative to the intrinsic permea-
bility of the materials discussed in
other sections of the paper. By finely
dividing the core material and using
80 permalloy which intrinsically has a
low hysteresis loss, coils peculiarly
suited to the loading of transmission
circuits may be produced. The fine
dust particles are coated with a thin
insulating film and are compressed
into suitable ring cores under a pres-
sure of about 200,000 pounds per
square inch. The coils made from these
permalloy dust cores have extremely
small losses and their characteristics
continue very constant in service.
These cores are also used in audio
frequency filter coils.

By the addition of certain elements
to ordinary carbon tool steel, mate-
rials of varying degrees of excellence
for permanent magnets have been pro-
duced. One per cent of chromium
added to ordinary carbon steel in-
creases somewhat its coercive force
and permits it to be hardened by
quenching in oil instead of water. This
is of considerable advantage in the
elimination of quenching cracks. The
coercive force of this steel is usually
between 40 and 50 oersteds. It is the
least expensive of the magnet steels
and is largely used whenever weight
is not of such importance as to pre-
clude a magnet of sufficient length to
retain its strength. This steel is large-
ly used in magneto-generators, coin
collectors and ringers.

By the addition of approximately
4% instead of 1% of chromium a
magnet steel of still higher coercive
force is produced. Its coercive force

is in the neighborhood of 70 oersteds..
This is also an oil hardening steel and
because of its freedom from quenching
cracks and its lower cost it has largely
replaced the earlier 5% tungsten steel
which is a water quenching steel and
which has similar characteristics. This
steel is also largely used where the
slightly higher cost is not a determin-
ing factor or where a somewhat
shorter and consequently lighter mag-
net is demanded, for example, in
polarized relays and some of the more
recently designed ringers.

Cobalt steel, invented by Professor
K. Honda of Japan, marked a decided
advance in permanent magnet steels.
It contains about 35% cobalt, 7% or
8% tungsten and 3% chromium. The
carbon content is about the same as
that in other magnet steels. The
coercive force of this steel is more than
three times that of the 4% chrome
steel and consequently it is very re-
sistant to demagnetization. Magnets
made of it may be very short and still
be of satisfactory strength. It is em-
ployed extensively in receivers and
other high class instruments. The
only drawback to its more extended
use is its cost which is some twelve or
fifteen times that of the 4% chrome
steel.

In the processes of rolling or draw-
ing soft magnetic materials their
structure is strained and distorted,
and this greatly decreases their per-
meability and increases their coercive
force. This condition may be relieved
and the normal magnetic qualities
obtained by a proper heat treatment
which differs somewhat with different
materials. In general, the process con-
sists in heating them at the proper
temperature for a given time, sealed in
metal boxes which are then allowed to
cool slowly. As might be expected,
the magnet steels require hardening

by quenching in water or in oil from a
definite temperature.
In the investigation of all these
magnetic materials there has been in
the past an immense amount of work
which is the basis of our present de-
sign information on magnetic appara-
tus. All of the materials have been
improved in their properties, but the
most remarkable achievements have
been in the development of the perm-
alloys for high permeability and of

A new day has thus come in design
and a new field for improvement has
opened before the designer with each
development of magnetic materials,
The continuation of present investiga-
tions which are relating more com-
pletely the physical condition and the
chemical constituents of a material
to its magnetic properties gives prorn-
ise of even greater developments in
the future.

substance is known to be
entirely impervious to it. The life of
plants and animals may be said to
depend on the diffusion of water
through their cell walls, and it is a
familiar fact that the water which
permeates the human body forms its
largest single constituent. Water
passes through materials often con-
sidered water-proof such as rubber,
asphalts and waxes.

In the Bell System a number of
organic materials are used as insula-
tions which often are exposed to mois-
ture. Although the actual quantity
of water which diffuses through most
organic substances is small, this small
amount becomes important in con-
densers, coils and terminal boxes and
other apparatus which must be pro-
tected over a period of years.

insulations which are to be exposed to
moisture is the measurement of the
quantity of water absorbed. Such
measurements do not always give a
complete picture of water-proofing
characteristics, since a considerable
amount of water may diffuse through
a layer of material into some interior
space and only a small amount re-
main absorbed in the outer layer.
Differences in molecular structure,
phase relationships, and crystalline
state may play important roles in
diffusion, and often the absorption of
water does not appear to be the prin-
cipal controlling factor.

Of the general methods for de-
termining the rate of diffusion of water
through a layer of a substance, prob-
ably the most simple and direct is to
establish on one side a concentration
of water vapor, maintain on the other
side a lower concentration, and mea-
sure the amount of water which passes

Fig. 1—Water vapor passes from the interior of the aluminum
cell through the rubber sample into a drying agent outside

through the material in a given time.
A convenient way to do this is to seal
a sheet of the material across a cup or
cell in such a manner that moisture
passes from the cell through the sam-
ple into a drying agent outside. For
such measurements several types of
cells are used in these
Laboratories depend-
ing on the nature of
the material.

For rigid and semi-
rigid substances like
soft and hard rubber,
phenol fibre, cellulose
derivatives, and many
plastics, an aluminum
cell is used in which
the sample is held in
place by an aluminum
pressure ring, the seal
being completed by
suitable washers coated
with petrolatum (Fig-
ure I). The cell is
placed in a dessicator
containing a drying
agent and maintained
at 25° C. by immersion
in a water bath (Fig-
ure 2). The loss in
weight of the entire
cell combination is
taken as the amount of
water which has dif-
fused through. Mois-

For substances hav-
ing a tendency to cold
flow, such as asphalts,
the cell shown in Fig-
ure 3 is used. The as-
phalt is supported by
a thin alundum disc,
and the drying agent
is supported on a cali-
brated quartz spring whose elongation
indicates the amount of water which
has passed through.

A third type of cell is used for mate-
rials having a very low diffusivity
and which require an extremely tight
seal. Such a cell may be constructed

Fig. 2—The temperature is held constant during a diffusion
test, often by keeping the cells in a desiccator immersed in a

by making a thick-walled wax cup
across the mouth of which a thin disc
of the material to be measured may be
sealed. The sealing is accomplished
by melting together the edges of the
cup and the disc, if the disc is of wax,
or by melting the cup around the edge
of the disc if the latter cannot easily
be melted. The water which passes
through is collected by a drying agent
attached to a calibrated quartz spring,
as shown in the picture at the head of
this article. The temperature is kept
constant by placing the apparatus in an
air bath or constant temperature room.

Most materials obey quite closely
the linear diffusion law established by
Fick, and since the factors which enter
into linear diffusion are definite and
measurable, the law is particularly
applicable from an engineering stand-
point. It states substantially that the
amount of vapor diffusing through a
unit area of a material in unit time is
proportional to the difference in vapor
pressures on the two sides and in-
versely proportional to the thickness.
The constant of proportionality, or dif-
fusivity, constant depends principally
on the nature of the material. The
law is somewhat analogous to Ohm’s
law; the differential vapor pressure
corresponds to the electromotive force,
and the flow of water molecules driven
by it is checked by the “resistance”
of the material. Diffusivity is thus
analogous to conductance.

Fig. 3—When a material with a tendency to
cold-flow is placed in a diffusion cell, it is
usually supported by an alundum disc

cellulose acetate, if plotted on this chart would
appear as a bar extending to 160

The diffusivity constant of a mat-
erial is taken as the number of grams
of water which pass through a one
centimeter cube in one hour under a
vapor-pressure difference of one milli-
meter of mercury at a definite tem-
perature.

Organic materials whose diffusivity
constantsat 25°C. have been measured
in the Laboratories include soft and
hard rubber compounds, submarine
cable insulations, phenol fibre and
similar materials, cellulose acetate and
related substances, asphalts, and pure
hydrocarbons such as_ polystyrene.
The amount of water which diffuses
through a centimeter cube of material
at 25°C. ranges between 10° and 10°
grams per hour when the difference in
vapor pressures is one millimeter of
mercury (Figure 4).

Measurements of this sort have
proved especially valuable in dealing
with rubber, asphalts, and waxes,

which are used extensively in the Bell
System as insulating materials, pri-
marily to provide protection from
water. The amount of material
needed for protection has hitherto
been determined largely empirically,
but a knowledge of the rate at which
water passes through an insulation
now makes it possible to estimate the
thickness needed to protect a piece of
apparatus for a specified length of
time under known conditions of tem-
perature and humidity. The mini-
mum thickness of rubber sheath neces-
sary to protect a dry-core paper cable
can be calculated, for example, and
the amount of material required in
sealing apparatus with an organic
substance can be estimated.

The mechanism by which water
diffuses through solid materials is not
definitely known. There are some
data on the diffusion of gases through
inorganic substances, however, which
help to explain similar processes in
organic materials.

There are indications that sorption*
plays an important part in some cases
of the diffusion of gases through
inorganic materials. Hydrogen dif-
fuses into copper only after it has first
been adsorbed on the copper surface,
and palladium sorbs hydrogen so
strongly as to indicate that they com-
bine chemically. On the other hand,
diffusion independent of adsorption

seems to be exemplified by the Passage
of inert gases through fused silica
where the gas molecules are believed
to enter extremely minute cracks in
the film directly from the gas phase.
The diffusion of moisture through
certain organic substances such as
polystyrene and hydrocarbon wax, is
associated with very little absorption.
The amount of water absorbed by
polystyrene is extremely small, al-
though the diffusion of water through
it is comparatively large. The water
absorption of the wax is also small,
yet its diffusivity is only about one
fortieth of that of the polystyrene.
Both materials are homogeneous, non-
polar compounds. The difference be-
tween their diffusivities appears to be
due to differences in their physical and
chemical structure of some other sort
than those determining sorption. In
sharp contrast is the case of cellulose
acetate, through which moisture pas-
ses 1600 times as fast as through
hydrocarbon wax. Here the sorption
of water is strong and probably bor-
ders on chemical union, as does the
interaction of palladium with hydro-
gen. It is very likely that the higher
sorption affects the diffusivity, and
that both are largely accounted for by
the same features of chemical structure.
To arrive at a true picture of
the mechanics of moisture diffusion
through organic substances much ad-
ditional work is required. The mea-
surements made in these Laboratories
form only a beginning in this direction.

President, American Telephone and Telegraph Company in charge of develop-
ment and research, and President of Bell Telephone Laboratories.

In Honor oF Dr. JEWETT, upon his
completion of thirty years of service in the
Bell System, a luncheon was arranged in
the twelfth floor conference room on
September 13th, and attended by engi-
neers who had been closely associated with
him on the projects for which he was
personally responsible in the early years
of his career, and by executives and de-
partment heads of the Laboratories.

Those present were Messrs. Colpitts,
Charlesworth, Norton, E. W. Adams,
Anderegg, Bascom, J. H. Bell, Blackwell,
Buckley, G. A. Campbell, Carson, A. B.
Clark, Curtis, Dixon, Englund, G. D.
Edwards, Farrell, Ferris, Fletcher, Fondil-

Also Messrs. Haislip, Hartley, Ives, R.
L. Jones, M. J. Kelly, Lowry, Mathes,
Mills, Moravec, Morehouse, W. H. Mar-
tin, Molina, Parker, Quarles, Sanford,
T. Shaw, Sheppard, G. B. Thomas,
Toomey, Warren, Webb, R. R. Williams,
R. H. Wilson and W. Wilson.

Absence from New York prevented the
attendance of Messrs. Espenschied, Heis-
ing, R. S. Hoyt, K. S. Johnson, Kendall,
Matthies and J. G. Roberts.

At the conclusion of the luncheon a
picture was taken of Dr. Jewett and those
members of the present Bell Telephone
Laboratories who had been associated

Dr. Fewett, surrounded by some of his early Boston associates, examines a cable loading

E. H. Colpitts; Standing, Left to Right—}. F. Toomey, E. C. Molina, Thomas Shaw,
O. B. Blackwell, H. S. Warren and H. P. Charlesworth

with him in the Boston laboratories of the
American Bell Telephone Company.

L. EspenscHIeD and R. A. as
representatives of the Bell System, sailed
to attend the International Technical
Consulting Committee on Radio Com-
munications (C.C.I.R.) in Estoril, Portu-
gal, September 22 to October 10. This
committee meets every two years to con-
sider the progress of the radio art, both
from the commercial and broadcasting
standpoints. It drafts technical recom-
mendations for the international Tele-
communications Conference which meets
every five years. The next international
conference which will have treaty-making
powers will be at Cairo in 1937. Among
the major questions to be considered at
Portugal will be the allocation of fre-
quencies to the different types of radio
services and means of reducing inter-
national interference.

Messrs. Espenschied and Heising trav-
eled by way of London where they at-
tended a Technical Session of the Inter-
national Scientific Radio Union (U.R.S.I.)
held September 11 to 19.

Dr. F. B. JeEwetr and Dr. W. A.
SHEWHART were guests of Lt. Col. Stuart,
commandant of the Picatinny Arsenal,
recently. After an inspection of the re-
search laboratories and manufacturing
activities of the Arsenal, Dr. Shewhart
discussed with Col. Stuart the application
of quality control techniques to the manu-
facture of munitions.

A THREE-WAY discussion on new aids
to education was recently broadcast over
the NBC network by Dr. Jewett, Dr.
Dearborn of New York University and
William D. Boutwell of the Office of Edu-
cation of the United States Department
of the Interior.

PRoBLEMS concerning radio equipment
have taken F. M. Ryan, D. K. Martin,
W. M. Knott, A. D. Liguori, J. G. Nordahl
and W. A. Woods to Washington at

various times to confer with members of
the Bureau of Engineering of the Navy
Department.

H. C. Atkinson, R. S. Barr and G. N.
THAYER accompanied the U.S. Fleet dur-
ing maneuvers off Newport, Rhode Island.

W. L. Tierney visited radio stations
KHJ and KFRC of the Don Lee Broad-
casting Company in Los Angeles and San

R. S. Hoyt, one of the members of the present
Laboratories who started in the Boston Lab-
oratories

J. C. Bain visited the Engineering and
Research Laboratories of the British Post
Office at Dollis Hill and “Broadcasting
House” of the British Broadcasting Com-
pany, Ltd. in London.

B. Leuve.ink visited the Northern
Electric Company at Montreal to take
part in conferences on radio broadcasting
transmitter design.

G. Martejxa visited Wright Field at
Dayton and the Western Electric Com-
pany at Hawthorne in connection with
radio equipment for the Army Air Corps.

J. F. Morrison completed a series of
radio field intensity studies of Station
WOR at Newark for the Bamberger
Broadcasting Service, Inc.

O. W. Towner supervised the instal-
lation of an ultra-high frequency radio
system for the Department of Public
Safety of the City of Newark, New Jersey.

J. E. Rances was at Hawthorne on
loading coil cases for use on loading pro-
gram transmission circuits. He also in-
spected other types of coil cases under
construction.

A. J. CorIsTOPHER visited Hawthorne to
discuss the manufacture of induction coils.

On THE monpéAy following the tragic
burning of the Morro Castle of the Ward
Line off the Jersey coast on September 8,
members of the Laboratories learned with
regret that among those lost was Miss M.
F. Moran of the Apparatus Development
Department. Miss Moran was returning
from a vacation cruise with her mother
who was also lost. She came to the Lab-
oratories on August 29, 1917. In 1918
she was made a laboratory assistant and
in 1927 a technical assistant. Shortly
after coming with the Laboratories she
was concerned in the construction and
adjustment of built-up condenser net-
works used in the Transcontinental Line
and became very skillful in the operation
of the capacity bridge. She continued

this type of work until 1926 when she
engaged in measurements, computing and
analysis of test data in connection with
laboratory investigations of cords, wire
insulation and switchboard cable. Miss
Moran took an active part in the Women’s
Bridge Club.

Joun J. Kuxyn, Manual Apparatus
Engineer, received a five-star button on
the twenty-third of last month, emblem-

atic of twenty-five years of service in the
Bell System. Mr. Kuhn joined these Lab.
oratories in 1909 as a member of the
drafting division of the Apparatus Design
Department, later transferring to the

special order division. When the Western
Union Company was for a time affiliated
with the American Telephone and Tele-
graph Company, he became concerned
with the design of telegraph apparatus.
The advent of the war supplanted this
activity with the mechanical design of
communication and signalling equipment
for the United States Government. At
the close of the war he retained super-
vision of this work and also took charge of
the mechanical design of repeaters, rack
mounted apparatus, telegraph equipment,
ticket distributing systems, and the like.
In 1927, when the Special Products De-
partment was organized, he took charge
of several groups responsible for the
mechanical design of amplifiers, audi-
phones, and government apparatus, and
two years later his responsibilities wid-
ened to include the development of
mechanisms employed in recording and
reproducing sound pictures. Last year
he transferred to the Telephone Appara-
tus Development Department, taking
charge of the group which had been super-
vised by the late H. T. Martin. As
Manual Apparatus Engineer he is now
responsible for the design of coin col-
lectors, telephone booths, desk and wall

sets, plugs, jacks, keys, protectors, and a
number of different types of maintenance
and testing apparatus.

A QUALITY SURVEY on filters and net-
works took H. Whittle, A. N. Jeffries and
H. O. Wright to Kearny.

B. O. TEMPLETON discussed problems
connected with the manufacture of coin
collectors with engineers at Hawthorne.

A. K. Smit visited the New Jersey
Bell Telephone Company’s toll office in
Newark, New Jersey, in connection with
a service trial of apparatus for the pneu-
matic ticket distributing system.

J. R. TownseEnp inspected the experi-
mental installations of lead alloy cable
sheaths at Chester, Pennsylvania.

C. H. Amapon spent nearly a month
investigating the occurrence and extent of
decay in creosoted pine pole lines in
Tennessee and North Carolina.

A. W. Drinc spent a week in Phila-
delphia and Point Breeze in connection
with a new protector for the Bell Tele-
phone Company of Pennsylvania.

A. W. CLeMeEnT presented a paper en-
titled Line Filter for Wide Band Open
Wire Program System at the Pacific Coast
Convention of the American Institute of
Electrical Engineers held in Salt Lake
City. D. H. Keyes also attended this
convention and presented a paper Foint
Use of Poles with 6,900-Volt Lines of
which he was joint author with W. R.
Bullard.

C, Dorcan, who completed a
quarter century of service in the Bell Sys-
tem on the twenty-eighth of last month,
got his early telephone experience as in-
spector and as repairman of private
branch exchanges for the Southern New
England Telephone Company. At the
outbreak of the war, after nine years of
service with that company, he left his
position of wire chief to engage with an
outside concern in manufacturing and
testing telephone and signal apparatus for
the Army. In 1918 he returned to the
Bell System, this time joining the Western
Electric Company, in its Engineering De-

H. A. Larlee (left) talking over handset problems with F. L. Alden, development
engineer, at Hawthorne

partment which is now these Laboratories.
Here he first took charge of installing
radio telephones on the patrol boats pro-
tecting New York harbor. On the com-
pletion of the war, he joined a newly

formed group engaged in writing the
method of operation of the early panel
dial circuits. Later he engaged in relay
time studies, analyzing and testing the
circuits used in interconnecting the man-
ual and panel systems. Most recently he
has been engaged in laboratory work with
the carrier telephone group of the Toll
Systems Department.

H. S. Warren led a discussion on
grounding practices as embodied in Ar-
ticle 9 of the National Electrical Code
at the Eastern Section of the Interna-
tional Association of Electrical Inspectors
held at Washington.

AN INVESTIGATION of shielding against
low frequency induction in cable circuits
has been undertaken by H. R. Moore, B.
C. Griffith and J. H. Harding at Green-
ville, South Carolina. It is expected that
the investigation will take about three
months.

J. C. Davenport, Jr., has been in
Wisconsin for several weeks in connection
with the work of Project Committee 2J of
the Joint subcommittee on development
and research of the Edison Electric Insti-
tute and the Bell System. In this work he
is primarily interested in checking up on
the coupling between power and telephone

circuits to compare the estimated with
the observed values of induced voltage,

Joun A. McIntyre received a seven.
star service emblem on the twenty-eighth
of August, emblematic of thirty-five years
of continuous service with the Bell Sys.
tem. Mr. McIntyre joined the Ameri.
can Bell Telephone Company in 1899,
entering its Boston Laboratory, a parent
of these Laboratories. Four years later
he came to New York to take part in the
inspection activities of the American Bell
Company at West Street, and continued
in this work after it was taken over by the
Western Electric Company in 1907,
When the Manufacturing Department
and its associated inspection activities
moved to Hawthorne in October 1913,
Mr. McIntyre remained at West Street
with the Engineering Department, engag-
ing in the construction of transmitter and
receiver standards conducted by the Re-
search Department. Five years ago he
transferred to the Apparatus Develop-
ment Department where he has since

H. PFANNENSTIEHL was in Rochester in
connection with sound picture equipment.

where he is engaged in inspecting the
announcing system for the U.S.S. Nevada.

R. A. Mitter and W. Herriortr visited
Nela Park to discuss exciting lamps for
sound picture machines.

R. A. Mitier and H. C. Rusty discus-
sed the design of a special synchronous
clock system for the New York Telephone
Company with engineers of the Telechron
Company at Ashland, Massachusetts.

H. C. Curt and R. L. Hanson were in
Norfolk, where they made a sound survey
on the U.S.S. Ranger.

D. G. BLaTrner was aboard the U.S.S.
Ranger in Norfolk, Virginia, for the in-
stallation of new loud speaking apparatus.

R. M. Burns visited the Naval Re-
search Laboratory near Washington in
connection with storage battery develop-
ments.

ATTENUATION MEASUREMENTS on over-
head cables have been made at Ticon-
deroga by H. H. Benning and M. S.
Burgess. Recently S. Brand, A. G. Jen-
sen, P. Mertz and T. Odarenko visited
Ticonderoga to confer with the engineers
doing the work.

In 1905 Cart H. Hircucock left the
University of Chicago, and the following
year joined the Western Electric Company
at Clinton Street, beginning a period of
service in the Bell System which reached
the quarter-century mark on the second
of August. After short periods with its
Inspection Department, and with the
National Packing Company, he came to
New York to take the student course of
the New York Telephone Company. In
1910 he transferred to the Engineering
Department of the Western Electric
Company, now these Laboratories, where
he engaged in inspection work at West
Street and at the plant of the Simplex
Wire and Cable Company in Boston.
Following this he joined the lead covered
cable development group at Hawthorne,

later shifting with a part of this group to
the Kearny plant, and has participated in
many of the cable development projects
of this period, including that of the unit-
type cable which is now standardized.

A sTupy OF interference at high fre-
quencies took E. I. Green, F. A. Liebe,
R. G. McCurdy, T. Odarenko, R. A.
Shetzline and M. E. Strieby to Phoenix-
ville, Pa., where Mr. Odarenko has been
investigating and measuring radio inter-
ference and static on open wire lines and
carrier cables.

M. E. Srriesy visited the Point Breeze
Works to inspect high frequency cables.

J. R. Witson and V. L. Ronct visited
the Corning Glass Company, on prob-
lems of glass development.

C. H. Prescotr and J. O. McNa.ty
were in New Haven for the field trial of a
new repeater tube.

J. A. Becker visited the Westinghouse
Electric and Manufacturing Company
and the Union Switch and Signal Com-
pany in Pittsburgh, to discuss with the
engineers of these companies the prob-
lems arising in the manufacture of copper
oxide rectifiers.

ALTHOUGH RoceEr G. RamsDELL, who
received a five-star service emblem on
the first of August, has been with the
Bell System for twenty-five years, his
membership in these Laboratories is only
a few months old. Mr. Ramsdell received
from the University of Vermont the B.S.

degree in Electrical Engineering in 1909
and immediately came to New York to
join the Engineering Department of the
American Telephone and Telegraph Com-
pany, then headed by the late John J.
Carty and located at 15 Dey Street. In
1919, when the Department of Develop-
ment and Research was formed, he trans-
ferred to its equipment development sec-
tion with which he remained connected
until the consolidation of the D. & R.
Department with these Laboratories last
spring. He has been principally concerned
with the development of central office
apparatus, more particularly of switch-
board jacks, plugs and cords, and the
tools and gauges required in the field to

maintain this apparatus. He is con-
tinuing this work as a member of the
Local Facilities group of the Systems De-
velopment Department.

AvotpuH R. Swosopa received the B.S.
degree from the University of Nebraska
in 1903. He immediately joined the
Student Course of the Western Electric
Company at Clinton Street and at its
conclusion came to West Street as a
switchboard inspector, soon taking up the
design of power plants for central offices.
Returning to the University he obtained
the E.E. degree in 1907 and after a four
year period with the Kellogg Switchboard
and Supply Company rejoined the West-
ern Electric Engineering Department at
West Street. The bridging of this gap in

service made Mr. Swoboda eligible for a
five-star service emblem on the fifth of
August. An early connection with the
Physical Laboratory was followed by
work with groups developing public

K. K. Darrow presented a paper en-
titled Nuclear Chemistry before the Chem-
ical Education Division of the American
Chemical Society at Cleveland.

J. A. Manoney returned on September
4 from Australia, where he cooperated in
furnishing technical information to the
Australian Post Office Department on a
proposed Australia-Tasmania submarine
cable to provide telephone, telegraph and
radio broadcast program channels from
Melbourne, Australia to Launceston and
Hobart, Tasmania.

V. T. CALLAHAN visited the Sturtevant
Company at Boston where he conferred
with engineers on tests of ventilating equip-
ment for an exchange power installation.

F. S. Enrz spent a week in Princeton,
and Stroudsburg, Pennsylvania, inspect-
ing the pilot-wire regulating system.

1. G. Witson visited Atlanta, Green-
ville, and Charlotte arranging for the
return from these stations to the Lab-
oratories of the experimental models of the
new carrier telephone repeater using a
two-way single amplifier. A service trial
during the past year was recently suc-
cessfully completed.

E. C. Mouina attended the summer
meeting of the American Mathematical
Society at Williams College the week of
September 3.

C. S. Demarest and W. J. Heirsmiru
were present at the cutover of the step-
by-step and toll central office in Roanoke,
Virginia. The power plant for this
central office is the initial installation of
the full-automatic type.

O. H. Loynes recently completed the
law course of the LaSalle Extension Uni-
versity and was awarded its LL.B. degree.

Wuitney visited Columbus and
Des Moines for the purpose of discussing
community dial terminations in toll
offices.

Wuen R. Barney was grad-
uated from Cornell University thirty
years ago, he immediately entered the
Clinton Street Works of the Western
Electric Company, and joined the Stu-
dent Course. After the survey of the
various branches of the Company’s activ-
ity afforded by that course, he was asso-
ciated with the Engineering Department,
taking part first in the equipment branch
and then in the inspection of manufac-
tured products. After the depression of
1907 he joined the sales organization to
help dispose of overstocks by converting
them into other types of apparatus or
equipment. Later he served as the Haw-
thorne representative on matters per-
taining to new and changed apparatus,
first for the Sales Department and later
for the Merchandise Department. In
1913 he came to New York as a member
of the Advertising Department to take

charge of the work on the card catalog
which still occupies him. When the Ad-
vertising Department was transferred to
195 Broadway, he remained at West
Street where as a member of the Lab-
oratories he continues the task of main-
taining a card-catalog file of up-to-date
information regarding all coded apparatus
which the Western Electric Company
manufactures for sale to its customers.

On Avucust 11 Alfred C. Merriam,
better known among his many friends as
“Jerry”, joined the little band of those
who have served the Bell System for forty
years or more. Mr. Merriam entered
the toll rate department of the American
Telephone and Telegraph Company in
1894. Six years later he went to the
Purchasing Department of the Southern
Bell Telephone and Telegraph Company,
and when its headquarters moved further
south in the fall of 1901, he transferred to
the Cost Department of the Western
Electric Company. In 1913 he became
supervisor of the Payroll Department at
West Street. The following year the
manufacturing organization moved to
Hawthorne, and Mr. Merriam moved
with it, as a supervisor in the Cost De-
partment.

In the Winter of 1917 he returned to
West Street, to take charge of a cost group
in the Engineering Department, now these
Laboratories. Later he supervised the

Shop, and in 1929 rejoined the Account-
ing Department at West Street. His
familiarity with Tube Shop activities
brought him again to Hudson Street to
handle accounting work there, until the
transfer of tube manufacture to the West-

ern Electric Company last spring, when
he returned to the expense accounting
group here.

THE TRIAL installation of a new grid-
battery supply unit for voice-frequency
carrier telegraph systems took V. P.
Thorp to Pittsburgh.

A. H. Incuis has been in Chicago two
weeks studying the effect of reducing
noise in the operating rooms of Chicago
central offices.

E. S. Witcox has completed the check-
ing of transpositions on the Fort-Scott-
Wichita line and is now making cross-
talk measurements at 100 kilocycles.

E. D. Guernsey recently completed
noise and balance measurements on the
Joplin-Tulsa line and is preparing to make
similar tests on the Fort Scott-Wichita
line.

A. D. Fow er has been in Cleveland
for several weeks supervising and testing
equipment in the toll office associated with
standard frequency service which is being
initiated on a trial basis for the Cleve-
land Electric Illuminating Company.

A FIELD TRIAL of narrow open wire
spacing which is being conducted on a
twenty mile section of the New York-

Scranton line took R. S. Alford, J. A,
Carr, R. C. Edson and J. W. Kennard to
Mount Pocono, Pennsylvania.

E. P. FELcn and H. S. WIinBIGLER have
gone to Kansas City to prepare for delay
measurements on telephotograph circuits
in cooperation with engineers of the Long
Lines Department. Similar work is being
done in New York City by F. R. Dennis,
R. S. Hawkins and P. F. Jones with an
engineer of the Long Lines Department.
K. W. Pfleger is coordinating the work of
both groups.

SHORT RADIO WAVES, used in inter.
national transoceanic communication, are
variable in their effects and greatly in-
fluenced by magnetic storms, which in
turn appear to be due to solar activity.
The Azores have been chosen as a con-
venient point from which to make ob-
servations on the effect of such storms,
particularly their influence on the short
waves in transit between America and
Europe. C. F. Edwards left August 11 on
the S. S. Saturnia, and took with him
suitable measuring apparatus for the pur-
pose of making such observations over a
three or four months’ period. This is
being done with the knowledge and con-
sent of the Portugese administration
which is, of course, interested in radio
transmission.

ANDREW ALLAN, a retired member of
the Laboratories, died on September 8,
1934 following an automobile accident.
Mr. Allan, whose service dated from April
18, 1910, was formerly in the Plant De-
partment and was retired on September
I, 1932.

S. B. Kent attended a hearing before
the Examiner of Interferences in Wash-
ington.

R, J. FLuskey received an E.E. degree
from New York University, his alma
mater, last June.

Tue Lasorarories learned with regret
of the death of Lewis Kubic on August 26.
On April 26 Mr. Kubic had completed
twenty-four years’ service with the Lab-
oratories. During that time he was

employed as an instrument maker in the
development shop of the Plant Depart-
ment. During the last few years he had
spent considerable time in making dials
and other machine switching apparatus.

An EcHo of the Laboratories’ exhibit at
Cambridge last Winter* was an editorial
description of the magnetic speech re-
corder in the Boston ‘“‘Record” recently.
Under the caption “Park Your Voice” the
editor imagined several forms of domestic
and public discourse which might well be
“parked” indefinitely. Developing that
idea, he suggested to angry people, “Park
your voice within yourself—until you are
convinced that it should be released”’.

PRomPTED BY reading H. A. Frederick’s
article, “Early Handsets”, in the REcorp
for last July, Robert G. Brown, inventor
of the first commercial handset, paid the
Laboratories a visit last month. Mr.
Brown was especially interested in the
historical museum, through which its
curator, W. C. F. Farnell, guided him,
recognizing there not only the handset
models directly following his own but
many types of central office equipment
with which he was concerned as chief
operator in the 1870’s of the first exchange
of the Gold and Stock Telegraph Company.

B. Simon completed twenty
years of service in the Bell System on the
seventeenth of last month.

five years of service with the Western
Electric Company and these Laboratories.
Mr. Broadwell went to Hawthorne im-
mediately on receiving the degree of B.S.
in Electrical Engineering from the Uni-
versity of Pennsylvania. After a year in
the Student Course there, he entered a
branch of the apparatus design depart-
ment then located at Hawthorne, and in
1912 this work brought him to New York.
In 1915 he transferred to the dial appa-
ratus group. During the war he was
concerned with vacuum tube develop-
ment, but later he reengaged in the
design of various units for dial and toll
telephone systems. Among these were a
series of motor-driven interrupters for test
and service in dial circuits, and motor-
driven transmission regulating equipment
for controlling the effects of temperature

THE FALL SEASON of the Men’s Bridge
Club is being opened with a Mitchell
tournament for pairs, similar tournaments
being held weekly until Christmas. The
club has also entered a twelve-man team
in the newly organized Bell System
Bridge League consisting of teams from
the A. T. & T. Company, Electrical Re-
search Products, Inc., Western Electric
Company and the New York Telephone

Company. The Laboratories has again
entered the Metropolitan Commercial
Bridge League with another twelve-man
team to play matches bi-weekly.

The Women’s Bridge Club is also open-
ing its fall season this month with pro-
gressive contract and duplicate contract
tournaments held on alternate Mondays.

DuRING THE MONTH of August patents
were issued to the following members of

H. F. Smith at the land transmitter testing the effectiveness
of ultra-short waves for communication with vessels in
New York Harbor

ATISFACTORY transmission
requires, among other things,
that the overall loss of the tele-
phone circuit must remain reasonably
constant over long intervals of time.
This constancy of transmission loss,
unfortunately, is not an inherent prop-
erty of most transmission lines that
are in use, and so it has been found
desirable on the longer lines to provide
means for the regulation of transmis-
sion loss within suitable limits.

The attenuation of open-wire line
conductors increases with frequency.
The rate of increase is proportional to
the a-c resistance of the pair and to the
conductance. Both of these factors
increase with frequency and as a re-
sult the transmission loss does so also.
At the higher frequencies, which are
used for carrier transmission, the loss
is considerably greater than at voice
frequencies. Of more importance,
however, is the fact that both the re-
sistance of the pair and the conduc-
tance between wires do not remain
constant but vary considerably from
time to time with the prevailing
weather conditions, and the variation
in attenuation is of sufficient magni-
tude to require correction.

This variation in transmission loss
is due to two causes. First’ and most
important is the change of leakage at
the insulators. Of secondary impor-
tance is the change of conductor resis-
tance with temperature. The former
is peculiar to the open-wire form of

line construction in which the insula-
tors are fully exposed to weather,
while the latter effect is present in all
copper line conductors. Already im-
portant strides have been taken to
reduce the change of insulator leakage
with weather by the design of im-
proved types of insulators, but con-
siderable remains to be done before
this source of variation can be elim-
inated.

Occasionally, the insulator problem
is aggravated by unusual weather con-
ditions which are sometimes encoun-
tered in certain parts of the country.
These conditions may be caused by
sleet building up a wet ice coating
over the insulators, thus forming a
wet path between the wires at each
crossarm. Another serious condition
encountered in small areas in the far
west is the building up of a frost coat-
ing on wires and insulators. This
coating sometimes becomes several
inches thick and increases the line loss
per unit length tremendously. Still
another is the effect of sudden fogs in
regions such as the part of the central
transcontinental line normally subject
to salt dust deposits on the surfaces of
insulators. The dampening of this
salt dust by the fog on the insulator
surfaces causes a large increase of
leakage and consequently of trans-
mission loss.

While these unusual effects are
interesting and now and then quite
serious, the variations of transmission

the attenuation change
0.20 from the wet to dry
as iw condition is much more
2 ~ wa important than the va-
0.16 riation due to tempera-
j
ture. Figure 2 shows
| a record of attenuation
x .
© 0.12 sect oft taken at a single fre-
4 .
. ne] quency on a line 150
° = miles long, equipped
0.08 with S.P. insulators,
Bas and gives a continuous
| ween wet AND ORY | measurement for a 36-
< 004 ERENCE hour period. The
weather conditions at
DIFFERENCE FOR TEMPERATURE CHANGE OF 25F one end of the line are
T I I I I

loss even with ordinary change of
weather are sufficient to present a real
problem, especially in the longer sys-
tems. To illustrate the amount of
these variations, Figure 1 shows the
attenuation of an open-wire pair in
db per mile at different frequencies in
the range employed for carrier trans-
mission. One curve, the highest in the
figure, shows the average attenuation
during wet weather. The next lower
curve is the same characteristic during
average dry weather. It will be noted
that not only the transmission loss of
the line increases with frequency but
also the change in loss with the change
from wet to dry weather increases
with frequency. This differential is
plotted below the dry-weather atten-
uation curve. At the bottom oi the
illustration is shown the change in
attenuation with temperature for a
representative day. The maximum
change per day throughout a period
of a year might amount to twice this
in some localities.

noted along the time
scale. Evidently the
attenuation varies al-
most continuously and
sometimes quite rapid-
ly. In this case the total range of varia-
tion is nearly 4 db, which occurs within
a 12-hour interval. To show how this
range of variation compares with the
average curves of Figure 1, the broad
black vertical line at 25 kilocycles be-
tween the wet and dry curves has been
drawn in after being reduced to the
variation per mile. During the period
shown in Figure 2, the line was not
entirely dry nor did it show as large
an increase in attenuation during wet
weather as may frequently occur. The
S.P. insulators used on this line are an
old type and show about three times
the normal variation with weather
changes exhibited by the modern C.S.
type which are now standard for new
construction.

The length of line measured to pro-
duce Figure 2 was about average for
the spacing of repeaters on a type-C
carrier system. Evidently for a carrier
system operating over many sections
of line in tandem, averaging 150 miles
per section, the problem of varying
line attenuation is important. There

are a number of carrier systems em-
ploying 10 or more of such sections.
If the variations shown in Figure 2
were multiplied by 10, it would
amount to 39 db for the whole line.
Fortunately, these line sections, when
connected together, extend over such
wide areas that it is very unlikely the
same weather conditions will prevail
along the entire line and this reduces
the probability of obtaining large
variations of total line attenuation. It
is the reason, however, why a more
continuously and rapidly varying at-
tenuation can be expected on long
carrier systems, and makes more im-
portant the matter of providing suit-
able level indicators for the transmis-
sion maintenance forces so that proper
level corrections can be made.

Of course, there are other sources of
transmission variations which may
occur in the repeaters and terminals,
but these can and have been made a
small part of the total by suitable
design and maintenance.

sand miles or more in length have been
placed in service, an indicator of level
for maintenance purposes has been
employed. Nearly all type-C carrier
systems have been equipped with this
indicator, the so-called 1A pilot chan-
nel. A single-frequency pilot current
is located between channel bands and
as near the central part of the trans-
mitted range of carrier channels as
possible. To measure this pilot fre-
quency properly, tuned-rectifier me-
ters are provided at all intermediate
carrier repeaters and at the receiving
terminals. These meters are cali-
brated in db and are adjusted to
indicate ‘‘ Normal” level when normal
levels are transmitted on all channels
including the pilot. Deviations of
level can be noted and corrected man-
ually by the amplifier gain-control
potentiometers. Periodical observa-
tions of the meter readings at each
office are required as part of the reg-
ular maintenance procedure. At re-
ceiving terminals a sensitive marginal
relay is connected in series with the

Fig. 2—Variation of transmission loss of a section of open-wire line at 25
kilocycles due to weather changes

indicator meter to give an alarm when
the pilot deviates too far from normal.
By this means the maintenance per-
sonnel at the receiving terminal is
notified as soon as a major deviation
of the pilot level has occurred. Ina
long system, after an alarm has been
sounded, it is not known where the
fault is located, and to avoid making
the gain correction at the wrong
point, it is necessary to get in touch by
an order wire with each repeater office
to determine where a gain correction
should be made, and then to authorize
the proper adjustment. This does not
complete the adjustment. It merely
insures that the repeater gains are
correct at the pilot-channel frequency.

Referring back to Figure 1, one may
note that the variation of line loss
is different at different frequencies.
The gain correction by means of the
repeater-amplifier potentiometer, on
the other hand, is uniform at all fre-
quencies. This gain adjustment, there-
fore, is correct only at the pilot fre-
quency and leaves small differentials
to be added or subtracted at adjacent
channel frequencies.

When the change of line loss is
large and requires a number of con-
secutive steps from time to time, the
error at adjacent channel frequencies
will also become large. To avoid ac-

cumulation of excessive errors from
this cause, the receiving terminal
maintenance forces are required to
keep accurate account of the steps of
gain correction which have to be made
at all repeaters in the system, and
when these have accumulated suff_
ciently to justify correction of the
equivalents of the individual channels,
the corrections are made. This can
be done by manipulating potentio-
meters at the individual channel re-
ceiving terminals. <A table is em-
ployed for the corrections of this
kind, which is based on the attenua-
tion differential curve given in Fig-
ure I.

Very fortunately, this curve has
practically the same shape for all
gauges of line conductors and types
of insulators, so the same basic table
can be applied to all open-wire sys-
tems of the same frequency allocation
regardless of the facilities over which
the systems operate. Of course, the
correction in the individual channel
depends upon the frequency of the
pilot and the frequency of that chan-
nel, so the use of different frequency
allocations calls for different tables.

This transmission maintenance pro-
cedure is open to the objections that
it is complex and requires much time
to carry out, and that the smaller
variations of trans-

8
CHANNEL NO.2
\ lected. Under cer-
tain conditions these
5 prot {NORMAL small variations can add
than is sometimes. al-
“9 lowable. Difficulties
with the older system
such as this have led to

panion article.* In this system, des-
ignated as the 2A pilot channel, the
table of corrections has been replaced
by networks having the basic char-
acteristic shown in Figure 1.

Automatic control has the advan-
tage that it makes adjustmentsin much
smaller steps and makes communica-
tion between offices for the mainte-
nance of levels unnecessary. It also
provides level correction at all fre-
quencies at all repeater offices as well
as terminals and this is an important
advantage for the longer systems.
Records of the operation of systems
using 1A manual pilot-channel control
indicate that the maintenance of chan-
nel equivalents is ordinarily within the
*On the following page.

range of about 314 db either way from
normal for any channel of a system.
With the automatic control, this range
is reduced to 2 db, and generally a
much better figure even than this can
be realized.

Figure 3 shows the variation in loss
on two channels of the Washington-
West Palm Beach type-C system on
which the trial of the automatic pilot
channel was made. The recorded net
loss of channels 2 and 3 are shown to-
gether with the pilot level which was
automatically adjusted as soon as that
level departed more than 44 db from
normal. Evidently a much better
grade of transmission maintenance
can be obtained with the use of the
automatic pilot regulator.

Hysteresis Loop with superposed incremental loops taken on a ring specimen of 45 per-
malloy. Curves were made with Haworth Magnetic Curve Tracer. At intervals in the
process of tracing the hysteresis loop the rate of change of the magnetizing force was re-
versed for a predetermined increment and then the forward tracing of the loop continued

from day to day for a variety
of reasons, as discussed in an accom-
panying article*. Since the variations
at carrier frequencies if uncorrected
may be of sufficient magnitude to
seriously impair transmission, manual
adjustments—by aid of a device called
the 1A pilot channel—have generally
been required for the longer type-C
carrier systems. Although manual
adjustment has given satisfactory re-
*Page 49.

sults, considerable improvement, as
well as some economies in operation,
seemed to be possible if an automatic
pilot-controlled system were devel-
oped. As a result the 2A pilot system
has been made available, which auto-
matically adjusts the gain at each
carrier repeater station and at the
terminal at fifteen second intervals.

The system is like the 1A in that it
depends on the transmission of a
small amount of high-frequency pilot
current over the line from terminal to
terminal. At each station a portion of

this pilot current is selected by a
tuned circuit, and its level is measured
by a control meter calibrated in db
below and above normal level. If the
level departs as much as 14 db from
normal, a contact is made and a group
of relays and selectors act to adjust
the gain. Every fifteen seconds the

a bell when there is any abnormal
change in level of as much as 114 db.
A delay is incorporated in the circuit
so that the alarm is given only if the
abnormal change persists for thirty
seconds. This avoids having the alarm
operate on momentary transients.

FREQUENCY IN KILOCYCLES PER SECOND
Fig. 1—Position of bands, carriers, and pilot currents for the CS carrier system

control circuit operates the necessary
apparatus to insert in or remove from
the circuit attenuating networks in
quarter db steps if either of the con-
tacts in the indicating controller has
closed.

Besides the control circuit that
changes the gain whenever it deviates
as much as 14 db from normal, there
is at the receiving terminal an alarm
circuit that lights a lamp and rings

one-way carrier telephone channels
are provided; the three lower fre-
quency channels carry speech in one
direction, east to west, and the three
higher ones, in the other direction,
west to east. There is one pilot fre-
quency for each of the two bands
located about fifty cycles from the
carrier of the middle channel. The loca-
tion of the six channels, their carriers,
and the two pilot frequencies for the

L |
BAND | TRANSMITTING
FILTER | AMPLIFIER
HIGH-PASS
FILTER
=
BAND | | RECEIVING
FILTER | AMPLIFIER —
REGULATING
NETWORK DIRECTIONAL
DEMODULATOR | FILTER
TO"DEMODULATOR |
BAND FILTERS OF | PILOT“ conrroL | EQUALIZER
OTHER CHANNELS | --__] INDICATOR EQuiPMENT
| VOICE CURRENT --

Fig. 2—Schematic of terminal showing location of 2A pilot channel equipment

CS system are diagrammed in Figure 1.
The equipment required for the two
pilot channels, and its location in the
circuit, both at a terminal and at a
repeater station, is shown in the block
schematics of Figures 2 and 3. At the
terminal station the pilot oscillator
is located in the transmitting side
just ahead of the transmitting ampli-
fier. In the receiving side are the pilot
indicator, the pilot alarm, the control
equipment, and the regulating net-
work. At intermediate stations there
are in each branch a pilot indicator,
the control equipment, and the regu-
lating network. The pilot alarm at
intermediate stations is optional.

The oscillator, a schematic of which
is shown in Figure 4, must be very
stable in frequency and of constant
output. It may be tuned to the de-
sired location between channels, and
the output is set to the proper value
by an adjustable resistance network.
The pilot indicator circuit, shown
schematically in Figure 5, has a high-
impedance input circuit which is
bridged across the output of the re-
ceiving amplifier. Since the pilot

current is between adjacent channel
bands, the indicator circuit must be
sufficiently selective to prevent serious
interference into the pilot channel

from speech on the adjacent telephone
channels. This is accomplished by
two loosely coupled tuned circuits be-
tween the transformer and vacuum
tube. As shown in Figures 2 and 3,
the indicator circuit is tapped on the
output side of the main amplifier
while the regulating network is con-
nected in the circuit on the input side
of the amplifier. Any change made

PILOT |
INDICATOR |
|
CONTROL | |
EQUIPMENT |
|
| |
HIGH-PASS HIGH-PASS
EQUALIZER | WEST-EAST FILTER
DIRECTIONAL |REGULATING| AMPLIFIER DIRECTIONAL
FILTERS EAST-WEST NETWORKS FILTERS
AMPLIFIER EQUALIZER |
| |
| |
| CONTROL
| EQUIPMENT
LOW-PASS | LOW-PASS
FILTER | FILTER
t PILOT
|INDICATOR

Fig. 3—Schematic of intermediate station showing location of 2A pilot channel equipment

in the network as a result of the action
of the indicating controller will there-
fore act immediately to bring the in-
dicator back to the proper reading.

The regulating network is composed
of eight separate units. Four of them
each produce a nominal loss of four
db, one of two db, one of 1 db, one of
14 db, and one of 4 db. They are
connected in the circuit in series and
the control equipment acts to remove
from the circuit those that are not
needed. The attenuation units, with
the exception of the two smaller sizes,
introduce losses that simulate an
actual length of open line—the loss
increasing with frequency. The regu-

lating network thus builds out the
line attenuation to a fixed value for
any weather condition. This fixed
attenuation (line plus regulating net-
work), increasing with frequency, is
then closely equalized to an overall
loss-frequency characteristic that is
uniform with frequency by a base
equalizer network which is normally a
part of the repeater. This attenuation
correction with frequency equaliza-
tion is illustrated in Figure 6.

The control equipment consists of
three rotary type selectors, designated
A, B, and C, a group of eight relays
to cut in or out the units of the regu-
lating network, an indicating con-
troller, and certain other auxiliary

relays. A simplified schematic show-
ing the regulating network, the in-
dicator, and control equipment in
their relation to the amplifier and line
circuits is given in Figure 7. In the
indicating controller on the right are
shown the high and low contacts, one
or the other of which is closed by the
meter every 15 seconds if the level
differs from normal by as much as 4%
db. A third switch, marked trigger,
is also closed every fifteen seconds,
10 seconds after the operation of the
level meter, and completes the change
in the attenuation that has _ been
shown necessary by the previous oper-
ation of either the high or low contact.
If neither the high nor low contact
has closed, the subsequent trigger
operation produces no change in at-
tenuation, but if one of them has
closed, the circuit acts to increase or
decrease the loss introduced by the
network by 14 db. This sequence is
repeated every fifteen seconds and the
correction, if required, is always made
in 14 db steps.

The B selector controls the opera-
tion of the relays that cut in or out
the 1, %, and 14 db units. As the
selector is moved from positions I to 8

inclusive, with intervening trigger con-
tacts, the total loss introduced by
these units increases from 0 to 134 db
in quarter db steps. The C selector
on the other hand, controls the relays
that cut in or out the 2 and 4 db units,
and as it is moved from steps I to Io
inclusive, with intervening trigger
contacts, the loss inserted increases
from o to 18 db in 2 db steps. By
selecting the proper combination of
steps of these two selectors, therefore,
any loss from 0 to 1934 db may be
obtained. The A selector is employed
only when effective backward stepping
of the B or C selector is required in
reducing attenuation by a 4 db step.
Since the selectors will operate in only
one direction, the A selector, making
one revolution, acts as a master
selector to give the right number of
pulses or steps to the B or C selector
to step it forward one-half revolution
minus one step. Then when the trig-
ger contact operates, the attenuation
will be reduced by 14 db.

time there is 8 db inserted and the
high contact of the controller closses,
the B selector will move forward one
step. Then at the end of the 15 second
interval when the trigger switch oper-
ates, an additional 14 db loss will be
inserted in the circuit. Had the low
instead of the high contact closed, the
B selector would step under self-inter-
ruptions from the o db position to the
134 db position, while the C selector,
receiving pulses from the A selector,
would have been moved to reduce the
loss by 2 db. As a result a net change
of—14 db would be brought about
when the trigger switch operates.

The control circuit is also arranged
to give an alarm when the pilot cur-
rent suddenly becomes excessively low,
as would happen from an open or a
short on the line, and also on failure of
the automatic control. Provision is
also made for manual operation in
emergencies. With the 2A carrier
pilot control it is possible to hold the
overall loss between terminals to with-
in 2 db of the normal value.

F a beam of white light is passed
through a prism it will spread out
into a continuous colored band

spectrum, shading from red to violet.
This shows that white light is com-
posed of a great number of colors, and
that the wave length for each color is
different. An instrument called a
spectrometer is used to separate any
kind of light into its different colors or
wave lengths, and the process is
known as spectrum analysis.

In like manner the various com-
plex sounds which we hear are com-
posed of a number of simple tones of
different wave lengths, but each wave
length has a different pitch or fre-
quency. The acoustical research de-
partment of Bell Telephone Lab-
oratories has recently developed an
instrument which separates complex
sounds into their simple component
tones and at the same time indicates
their approximate amplitudes. By
analogy it is called an acoustic spec-
trometer.

The separation of complex tones
into their components is not new in
itself. With one method employed,

the component frequencies were de-
tected one at a time. Such a method
of analysis is applicable only to com-
plex tones that remain constant in
every respect while tests for the
desired frequencies are being made.
Another method, and the oldest one,
was to obtain a record of the wave
form, such as a tracing on smoked
glass or an oscillogram, and then by
mathematical analysis or by mechan-
ical means, determine the combination
of simple tones that would produce
the complex wave. This latter method
has the advantage that it is possible
to analyze tones of short duration.
The former method, while applicable
only to tones of relative long dura-
tion, is much faster.

The acoustical spectrometer re-
cently developed, is applicable to
tones of very short duration, and
shows all the components at the same
time. Instead of having a single
selective element which must be suc-
cessively adjusted to all the desired
frequencies, it has a large number of
selective elements each responding to
frequencies within a narrow range,

Fig. 1—Small spherical mirrors mounted on vibrating reeds reflect a ray of light
to indicate on a screen the component frequencies and their magnitudes

and all acting simultaneously. With
this new apparatus it is therefore pos-
sible to read or record at any moment
all the components present in any

complex tone. The analysis is ac-
complished by first converting the
complex sound waves into correspond-
ing complex electric currents. Tuned
reeds, electromagnetically driven, are
then caused to vibrate—each reed re-
sponding to components in a different
part of the frequency range.

Figure 1 shows a schematic arrange-
ment of the spectrometer. Light from
a lamp filament passes through a slit
and falls on concave mirrors which are
mounted on the tuned reeds. An
image of the slit is brought to a focus
on a screen by each

microphone, passed through an ampli-
fier and then on to the six magnets—
one for each octave. All the fre-
quency components that were in the
original sound will be represented in
the magnetic flux, and the reeds will
be set in vibration when there is a fre-
quency component that corresponds
or is close to their resonance fre-
quency. As the machine is now ar-
ranged, the spectrum may be watched,
or the glass screen may be replaced by
sensitized paper and _ photographic
records made. A motion picture
camera might also be employed to
photograph a changing spectrum.
The appearance of the record made
is illustrated by Figure 2, which shows

cal line. The length of
the line is a measure
of the amplitude of the
component, and the
position of the line
along the screen indi-
cates the frequency.

second by quarter tone
intervals. The reeds
comprising each octave
are driven by a single
long narrow electro-

Fig. 2—Spectrograms of various sounds indicate the dif-
ferent magnitudes of the various harmonics

a group of spectra for sounds of var-
ious types and pitches. In each case
there is a fundamental of low fre-
quency and a series of harmonics. The
amplitudes of the harmonics vary, and
it is this variation in the relative mag-
nitudes of the harmonics that gives
the difference in quality between tones
of the same fundamental pitch.

In the design of the apparatus, pro-
vision has been made for tuning each
reed accurately to its correct fre-
quency, and also for tilting the mir-
rors so that the dots of light from suc-
cessive reeds fall at equally spaced
intervals along a straight line. Their
amplitudes of vibration are also ad-
justed so as to be the same for the

The method and design that has
proved so satisfactory in this demon.
stration apparatus is easily applicable
to wider frequency ranges and smaller
frequency ratios between adjacent
With 48 reeds per octave,
which is readily obtainable, it is pos-
sible to detect components with fre-
quency differences of only *4 per cent,

This development provides a long-
wanted tool for studying the fre
quency components of sound of all
types. The rapidity with which re.
sults can be obtained by its use will, it
is expected, make it useful in the
acoustic studies carried on in these
Laboratories.

Cc. N. Hickman received the A.M.
degree at Clark University in 1917, and
then engaged in ballistic research for the
U. S. Government. At the close of the
war he was employed at the Bureau of
Standards in the Inductance and Capaci-
tance Laboratory. He then returned to
Clark University and received the Ph.D.
degree in 1922 under Dr. A. G. Webster.
Following a short period of service with
the Navy Department designing sub-
marine mines, he joined the Department
of Development and Research of the
A. T. and T. Company in 1924. In 1930
he joined the Technical Staff of the Lab-
oratories where he has been making a
study of magnetic recording.

F. F. Merrtam left Georgia Tech dur-
ing the war to engage in aircraft radio
work as a second lieutenant in the Army
Air Service. After the armistice he re-
turned to his studies, and completed the
course in electrical engineering in 1919.
Coming directly to the Laboratories he
worked on various electrical tests in the
Apparatus Development Department un-
til December 1919. He then transferred

to the Research Department and assisted
in the first ship-to-shore radiotelephone
development during 1920 and 1921. The
following year he left the Laboratories to
engage in radio merchandising in Atlanta,
Ga. and later in geophysical research in
Oklahoma and Texas. In 1927 he re-
turned to the Research Department of the
Laboratories, where he has since been en-
gaged in short wave and ultra-short wave
antenna development. He is at present
in charge of the group which is engaged
in this work.

D.M. Terry received the B.E.E. degree
from Ohio State University in 1920, and
at once joined the Technical Staff of the
Laboratories. Here he was first associated
with the Research Department, where he
worked on fundamental carrier research
and on the development of picture trans-
mission. He was in charge of the trans-
mitting apparatus in Cleveland for the
first public demonstration of this system
in 1924. Two years later he transferred to
the toll group of the Systems Department.
His work here has been chiefly on the de-
velopment of automatic control of trans-

D. B. HERRMANN entered the Labora-
tories in 1923. After a short time in the
messenger service, he transferred to the
Patent Department and then to the
Chemical Laboratories as a laboratory
assistant. In 1925 he left to attend the
College of the City of New York, return-
ing to the Laboratories for two summers.
He joined the staff of the Laboratories in
1928, and continuing his college work
received the B.S. degree in 1930. Here
he has been concerned with general prob-
lems of organic chemistry, particularly
those relating to rubber, balata, gutta
percha and like ingredients of submarine
cable insulation, and with measurements
of the dielectric properties of this and
other types of insulation. Recently he
has been occupied with studies of the
diffusion of water through organic insulat-
ing materials, and of the deterioration of
various substances by light.

AFTER GRADUATION by Cornell in 1903,
I. C. Pettit was for the next several years
an instructor in engineering for his alma
mater. On entering the Engineering De-
partment of the Western Electric Com-
pany in 1910, he at once began the work
on magnetic materials which has occupied
him almost continuously since. Among
his activities have been early measure-

ments on magnetic alloys; the application
of silicon steel to repeating coils; and
design of permanent magnets for tele-
phone receivers. He also participated in
the development work preceding the in-
troduction of the porcelain protector block.
Within recent years in the Materials De-
velopment group Mr. Pettit has been
responsible for tests and specifications of
all magnetic materials; for studies of the
large number of new magnetic materials
which have been invented in the Labora-
tories and elsewhere, and for their recom-
mendation to design groups for incorpora-
tion into telephone apparatus.

L. M. ILcenrrirz received a B.S. de-
gree in electrical engineering from the
University of Michigan in 1920, and at
once joined the Department of Develop-
ment and Research of the American Tele-
phone and Telegraph Company. Here,
with the Transmission Development
Group, he worked on the development of
all types of carrier telephone and telegraph
systems, and of gain control systems em-
ploying carrier pilot channels. With the
recent merging of the D. and R. and Bell
Telephone Laboratories, Mr. Ilgenfritz
becomes a member of the Technical Staff
of the Laboratories with the Transmission
Development Department, where he con-
tinues his studies in carrier problems.

Bell Laboratories Record 1934-10: Vol 13 Iss 2