C. W. Norwood 41
The N1 Carrier Oscillators, J. J. DeBuske 48 ,
Automatic Digit Recognizer 52

The AMA Computer: Chargeable Time and Message
Unit Computations, Mary E. Pilliod 53

Julian D. Tebo, Associate Editor
R. Linsley Shepherd, Production Editor
Theodore N. Pope, Circulation Manager

The BELL LABORATORIES RECORD is published monthly by Bell Telephone Laboratories, Incor-
porated, 463 West Street, New York 14, N. Y. M, J. Kelly, President; M. B. Long, Secretary
and Treasurer, Subscriptions: $2.00 per year; Foreign, $2.60 per year. Printed in U. S. A.

One of the many applications of the
cathode ray tube is its use in the laboratory
to permit the study of high-speed phe-
nomena. In this ane other uses of the tube,
simultaneous displays of several items of
information are frequently required and it
is highly desirable to provide a different
mark or identifying pattern for each item.
Letters and numbers make excellent desig-
nation marks for this purpose and the sym-
bol generator described here provides a
relatively simple way of producing a com-
bination of such characters on the face
of a CRO tube. A typical display of this
kind is shown in Figure 1. Although
the described method of forming these sym-
bols is new, the basic principle involved in
the process has been previously employed
by others.

Characters are formed on the CRO screen
by properly mixing selected wave-forms and
applying them in sequence, at a repetition
rate above the persistence of vision, across

the horizontal and vertical deflection plates
of the tube. If an ac voltage is applied
to the vertical plates, the trace will form
a vertical line on the screen. The length
of the line can be controlled by adjusting
the amplitude of the impressed wave, and
its position above or below a reference cen-
ter can be established by applying a suit-
able de voltage, upon which the ac wave
is superimposed, to one of the vertical plates
and connecting the other to ground. An ad-
ditional de voltage across the horizontal
plates makes it possible to adjust the posi-
tion of this vertical line to the right or left
of the reference center of the screen. Simi-
larly, a horizontal line of any desired length
can be formed and located by impressing
the ac voltage across the horizontal rather
than the vertical deflection plates. When
two or more of these lines are generated in
sequence they may be combined to form
simple straight-line characters. A “T” may
be produced by one horizontal and one

Fig. 1—A typical display of sixteen characters
formed by the symbol generator on the screen

Many letters and numerals consist en-
tirely of straight lines and can be formed
perfectly in this way. Other characters are
composed entirely or partially of curved
lines, which may also be generated. If a
sine wave, for example, is applied to the
horizontal plates, and a_ similar wave,
shifted 90 degrees in phase, applied simul-

taneously to the vertical plates, the resultant
trace will produce a circle, as shown in
Figure 2(a). In this diagram, the two wave
forms are represented with the zero axis
of each divided into eight equal time-inter-
vals. The lines extending from the axes to
the waves at the indicated intervals rep-
resent the amplitudes of the waves at these
selected instants. Another set of lines, paral-
lel to the axes, is plotted from the extremi-
ties of the corresponding pairs of amplitude
lines, and their points of intersection mark
the positions of the resultant trace at those
instants. The path of this trace describes
the indicated circle on the screen during
each cycle of the impressed signals. When
the voltage applied to the horizontal plates
is made smaller than that applied to the
vertical plates, the circle becomes an ellipse
and a well-proportioned “O” is produced.

If the horizontal signal, in the combina-
tion used to produce the “O”, is replaced
by a full-wave rectified voltage, the result
on the screen will be a well-formed “C”.
Figure 2(b) uses the method employed
in Figure 2(a) to illustrate the way these
two wave forms combine to form a “C”.
If these signals are interchanged and the
amplitudes suitably adjusted to elongate

Fig. 2—A diagram of the way in which wave forms applied to the horizontal and vertical plates
of a CRO tube combine to form a circle and a “C” on the screen.

the sides, the “C” will be transformed into a
satisfactory “U”. The symbol “D” is formed,
in a similar fashion, by applying a sine
wave across the vertical and a half-wave
rectified voltage across the horizontal plates.

In this symbol generator the wave forms
needed for each character are produced
entirely by the combination of a specially
designed miniature transformer and a pas-
sive network completely housed in a com-
pact plug-in container. A photograph of
one such unit, used to form the symbol
“C”, is illustrated at the left of Figure 3,
and the associated circuit diagram in Fig-
ure 4, The full-wave rectified voltage ap-
plied to the horizontal plates, is produced
through the use of two germanium recti-
fiers as shown in the lower branch of the
network in the diagram. The upper branch
of the network contains a conventional R-C
combination that shifts the phase of the
impressed 10-kilocycle sine wave by 90 de-
grees. The load resistor in each branch of
the network consists of two resistors in
series and the output is taken off across
one part of this voltage divider. The choice

of values for these two resistors, together
with the selection of the number of turns
in the transformer secondary windings,
determines the size of the character.

In the examples given above, the char-
acters can be formed by a single trace.
Some symbols, however, require two or
more traces to complete. The “P”, for ex-
ample, is formed by first producing a small
“D” as described and then adding a short
vertical line in the proper place. A “B”
consists of a combination of two “D's”; after
the first is formed, a second is placed di-
rectly below it. In all characters generated
by two or more elements, these elements
must be positioned accurately with respect
to each other. This is done by the use of
small fixed de bias voltages applied be-
tween the networks used to generate each
element and a common reference point.
AC voltages from additional transformer
secondary windings are rectified by ger-
manium diodes and filtered by R-C net-
works to provide these de bias voltages.
Adjustable positioning voltages applied be-

Fig. 3—Plug-in units that develop wave forms used in forming characters. The unit at the left

contains all the components required to generate the wave forms for a “C” and that on the

Fig. 4—Simplified schematic for the network used to
produce the wave forms for the letter “C”. This net-
work is shown at the left of Figure 3.

and ground will cause the character to
change position on the screen of the CRO
tube as these voltages are varied.

An example of a complex character is the
numeral “2” which requires two elements
in its formation. The first is a “C” oriented
to open downward and the second is the
element /. The first element is produced
by using the same type of networks used

Fig. 5—Switch assembly with contact plate removed
from one switch to show contacts and wiper arm.

to form the “C” and interchanging the sig-
nals on the horizontal and vertical plates.
The second element is formed by applying
a half-wave rectified voltage to the vertical
plates, produced through the use of a trans-
former secondary and a single germanium
rectifier, and a similar full-wave rectified
voltage impressed across the horizontal
plates. Two bias rectifiers are also used,
one in the vertical branch of the network
and the other in the horizontal branch to
position the two elements with respect to
each other. When the two elements are
combined on the screen, the result is a
well-formed “2”. The right-hand portion of
Figure 3 shows the unit used to generate
the wave forms for this numeral.

To produce the symbols that require
more than one element, or a display of sev-
eral characters, some arrangement must be
provided to paint the elements in the prop-
er order and in rapid succession. The
minimum frequency at which the succes-
sive elements must be retraced is deter-
mined by the persistence of vision of the
human eye and the storage effect of the
phosphor of the cathode ray tube. This
painting of more than one symbol is ac-
complished through the use of a motor-
driven three-pole, multicontact, rotary
switch assembly developed for the lab-
oratories by the Applied Science Corpo-
ration of Princeton, N. J. The switching sys-
tem is designed to apply the symbol gen-
erating wave forms to the horizontal and
vertical plates of the cathode ray tube.
After one element has been traced, the
switch applies the output of the next ele-
ment network to the tube and due to per-
sistence effects, the combination of these
two elements appears to form a complete
character. This process can be extended to
trace forty or more symbols, formed by
sixty elements in a display that appears si-
multaneous to the eye. The switch is also
used to brighten the traces while the sym-
bols are being generated and to blank out
the trace lines that would otherwise con-
nect the various characters and so tend to
obscure the pattern. A switch asse smbly con-
sists of three switches, each with a series
of sixty large and sixty small contact pins
arranged alternately in a circle on its con-

tact plate, and an associated wiper arm.
These arms are synchronized and driven
through a gear train by a common motor.
Figure 5 shows the motor, gear train, and
the three switches comprising a switch
assembly. The contact plate of one switch
has been removed to illustrate the details
of the contacts and the wiper arm. Figure
6 is a close-up view of this plate showing
the large and small contacts in detail.

One switch in the assembly is wired to
connect the horizontal output of the net-
works to the horizontal deflection plates of
the tube. The second connects the vertical
output to the vertical plates, and the third
is connected to provide brightening pulses
to the grid of the CRO tube.

The two switches used to apply the sig-
nals to the horizontal and vertical deflec-
tion plates are wired in such a way that only
the large contacts are active. Since the
large and small contacts are alternately
placed on the face of the contact plate,
the wiper arm will move off a live contact
and across a dead one before encountering
the next live position. By placing a dead
contact between the two live ones in this
way, transient short circuits that might be

CONTACT
r] CLOSED
VERTICAL
| TCONTACT SWITCH
OPEN
SWITCH
1 L_ OPEN
'
CLOSED
BRIGHTENING
SWITCH
OPEN

Fig. 7—A diagram showing the magnitude and time
soles of the open and close times of the hori-

caused by the wiper arm bridging a pair of
adjacent live contacts are eliminated. One
switch then, contains sixty active contacts,
each forming a path through the wiper
arm from a passive network producing a
horizontal or vertical wave form for one
symbol element, to a pair of plates in the
tube. The corresponding contact on a sec-
ond switch applies the associated wave
form to the other pair of tube plates. Since
each character requires either one or two
elements in its formation, such a unit is
capable of producing about forty symbols.
The actual number may be somewhat
higher or lower depending on the complex-
ity of the characters chosen.

As the motor drives the wiper arms
over the corresponding contacts on these
switches, a character element is displayed
on the screen. The arm remains in contact
with a particular pin for about 0.3 milli-
second and hence each element is formed
at least three times during this period by
a signal source of 10,000 cycles per second.
After the brushes have passed over the
dead contacts, the next element is formed
and this process is continued through the
complete cycle. It has been found that a
wiper arm speed of twenty cycles per sec-
ond paints each element sufficiently often
to remove all flicker when an amber filter
is used with a CRO tube which has P-7
phosphor.

The third section of the switch is used to
control the brightening of the trace pat-
tern. With this section in an off position,

VERTICAL LELEMENT 2
OUTPUT | | POSITIONING SYMBOL SYMBOL
/LELEMENT_!
HORIZONTAL ) LELEMENT 2 ]
OUTPUT POSITIONING | 1 HORIZONTAL VERTICAL
¢ yo'
a
SOURCE [ig
loz
VOLTAGE
SOURCE | Se] jNe
J } | \
\
\
| | | | \ -

Fig. 8—A simplified diagram illustrating the use of the switch assembly in applying the wave
forms for a single and double-element character to the CRO tube.

the voltage on the grid of the cathode ray
tube is adjusted to a point where the trace
on the screen is just extinguished. Then,
as the switch operates, it applies a positive
pulse to the grid of the cathode ray tube
which accelerates the electron stream suffi-
ciently to produce a visible trace on the
screen for the duration of the pulse. The
brightening switch is identical in design
to the other two in the group but is wired
with the small contacts active and the large
ones inactive. The three switches are syn-
chronized so that the wiper arms on the

THE AUTHOR: C. Wi.son Norwoop, a member
of the Military Electronics Department, joined the
Laboratories at the outbreak of World War II.
Prior to that he had his own business, a radio
shop, from 1927 until 1942. At the Laboratories
Mr. Norwood was assigned to work on Navy radar
equipment, After the war he worked on the
design of AM and FM broadcast transmitters, and
since 1947 he has been engaged in the develop-
ment of electronic apparatus for the government.

switches used in the horizontal and vertical
deflection circuits are in contact with large-
diameter contact pins at the same instant
that the wiper arm on the brightening
switch is in contact with a small-diameter
pin. Due to the difference in pin size, the
horizontal and vertical wiper brushes will
make contact first and break last. The
brightening pulse therefore is applied to
the CRO tube grid for a shorter period of
time than the symbol writing information
is applied to the deflection plates. Switch-
ing transients and noise produced when

the wiper brushes make and break contact
therefore do not appear on the CRO screen.
The path of the electron beam as it moves
from one symbol to the next would nor-
mally appear as a trace, but this is also
blanked out. Figure 7 shows diagrammatic-
ally the magnitude of the open and close
times of the three switches involved, and
their time relationship.

The diagram in Figure 8 illustrates the
use of this switch assembly in applying the
outputs of two sets of symbol networks to
the tube; one set for a single-element char-
acter and one for a double-element charac-
ter. For the single-element character, four
leads come from the network—two for the
horizontal wave form, and two for the ver-
tical wave form as shown in Figure 4. One
horizontal wave form lead terminates at a
contact on the horizontal switch and one
vertical wave form lead terminates at the
corresponding contact on the vertical
switch. The other horizontal and vertical
output leads are carried to ground through
the positioning-voltage sources. The bright-
ening voltage is applied to the correspond-
ing contact on the third switch from a sepa-
rate, adjustable, de source. As the wiper
arms touch these contact pins, the wave
forms are fed to the plates of the tube and
a positive pulse is applied to the grid to
make the resulting trace visible. The two-
element symbol is formed in a similar fash-
ion with the wave forms needed to produce
the first element applied to one set of con-
tacts and those required for the second

fed to the adjacent live contacts. Since the
wiper arms rotate at twenty cycles per sec-
ond, these elements are retraced every
twentieth of a second and at this rate, the
resulting image appears continuous.

The particular characters desired for a
display are selected through the use of
manually operated single pole switches
connected in the brightening circuit be-
tween the voltage source and the rotary
switch contact corresponding to each sym-
bol. By opening the appropriate switches,
the brightening voltage can be eliminated
from any desired contacts and the corre-
sponding symbols will not appear in the
display. This means that, although the
wave forms for all thirty characters are ap-
plied to the deflection plates, only those
selected by the operator are made visible.

As a means of producing letters and nu-
merals on a CRO screen, this symbol gener-
ator is simple and effective. In comparison
with methods previously used it requires
much less apparatus and appears to be
much more versatile in its application.
Present design calls for the generation of
the numerals 0 to 9 and the capital let-
ters of the alphabet. By use of the funda-
mentals here described, however, network
units may easily be designed to generate
the lower case letters, Greek letters or geo-
metric symbols as they may be required for
future applications.

The development work for this symbol
generator was done under contract with
the Bureau of Ordnance of the U. S. Navy.

Having completed a year's successful
trial, nation-wide customer toll dialing at
Englewood, N. J., is to be continued on a
regular basis by the New Jersey Bell Tele-
phone Company. During 1952, Englewood
customers dialed about 130,000 long dis-
tance calls, or more than 96 per cent of the
foreign area calls it was possible for them
to dial.

A microwave installation making net-
work television service available to York,
Pennsylvania, has been placed in operation
by Long Lines. Network service has also
been made available to Atlantic City, New
Jersey, by radio relay out of Philadelphia.
With the addition of these two facilities,
network programs are now available to 114
television stations in 71 cities.

Oscillators for the N1 carrier system must
meet the same general objectives estab-
lished for other components in the system
—reliable equipment and apparatus, rela-
tively low cost, small size, and ease of in-
stallation and maintenance. These objec-
tives have been realized and the oscillators
for the Type-N system have given very sat-
isfactory performance.

Two types of oscillators are required:
(1) those for use in terminals, where twelve
frequencies are required at intervals of 8
ke, starting at 168 ke up to and including
256 ke; and (2) those for group units and
repeaters, with a frequency of 304 ke. Since
the repeaters may be mounted on _ poles
along the cable route, their oscillators had
to be designed for operation over rather
wide variations in temperature and supply
voltage. The channel and group carrier os-
cillators, on the other hand, are located in-
doors, and thus are not subject to such se-
vere requirements.

Because of the need to hold the fre-
quency within + 25 cycles at 304,000 cy-
cles, quartz crystal oscillators* are em-
ployed. One basic oscillator circuit is used,
and the different frequencies are estab-
lished by inserting different crystals in the
circuit.

The equivalent electric circuit of a piezo-
electric quartz crystal is shown in Figure
1, where:

Electrically, the crystal is a “high Q”
(low loss) tuned circuit possessing series
and parallel resonances. By connection the
proper capacitance across the crystal and
using an electron tube to overcome the
circuit losses (including those of the crys-
tal), oscillations can be generated and
sustained. The frequency of oscillation is
determined by the crystal, but depends to
a small extent on the value of the circuit
capacitance shunted across the crystal.
During manufacture, the crystal is ground
and adjusted so that the series and parallel
resonances occur within the desired limits
of the nominal frequency for this crystal. If

this adjustment of the crystal resonance is
within the specified limits, the frequency
of the oscillator will be very near the right
value. Changes in temperature of the crys-
tal, however, change the frequency at
which it resonates, and thus the output fre-
quency of the oscillator. Crystals for the
304,000 cycle oscillator are thus adjusted
during manufacture to a resonance fre-
quency that is within 9 cycles of the desired
value, and variation in the resonance fre-
quency due to changes in temperature are
within + 10 cycles.

The circuit of the 304 ke oscillators for
both group units and repeaters is shown in
Figure 2. A 408A electron tube is used,

with feedback from the screen grid to the
control grid. The plate, or output, circuit is
electronically coupled to this oscillator, that
is, the electron stream between the cathode
and the plate is coupled to the electron
stream between cathode and screen so that
variations in this latter stream cause the
plate stream also to vary. This method of
coupling the load to the oscillator has the
major advantage that it practically elimi-
nates the effect, on the frequency of oscilla-
tion, of the load impedance connected to
the output terminals. This is necessary be-
cause oscillators supply the carrier frequen-
cies to copper oxide modulators, which
vary widely in impedance, and the fre-
quency of the oscillator must not be af-
fected by these variations.

None of the circuit components, except
for the crystal and capacitor C,, need be
held to close limits. The capacitors and re-
sistors are small in size and relatively in-
expensive; the most severe tolerance is + 5
per cent. The oscillator output transformer,
like the other transformers used in the Nl
system, is small, and inexpensive to manu-
facture.

The harmonic content of this type of os-
cillator is high, and thus filtering of the
fundamental frequency is re quired for re-
peater use. Part of this filtering is obtained
by designing the output transformer as a
tuned transformer, using capacitor C, to
tune it to the fundamental frequency. This
is a matter of economics — it is much less
expensive to build a capacitor within 1 per
cent limits than to hold the inductance of
the transformer to close limits. The remain-
der of the harmonic — is done by the
filter circuit containing L.,, C,,, C,,.

To obtain the accuracy inherent in the
crystal in the complete oscillator, there are
two conditions that must be realized at the
crystal: both the magnitude of the oscillat-
ing voltage applied to the crystal, and the
capacitance of the circuit terminating the
crystal must be held within specified lim-
its. In the oscillator circuit of Figure 2,
r, and c, form the screen load impedance,
and in part determine the magnitude of the
oscillating voltage applied to the crystal.
Capacitor c,, in addition to blocking the
de screen voltage from the crystal, couples

the signal from the screen grid of the tube
to the crystal. Grid leak bias for the con-
trol grid is provided by c, and r, and, with
the crystal and capacitor c,, form the feed-
back circuit.

When power is applied to the tube, the
circuit will oscillate at a frequency some-
where between the series and_ parallel
resonance of the crystal depending on the
value of the total shunt circuit capacitance
as determined by c,, c,, c,, and the grid-
cathode and scroen-cathode capacitances
of the tube. With the tolerances of the com-
ponents used, (including the crystal) the
accuracy requirements of the oscillator have
been met. The only elements, other than
the crystal, which influence the frequency
are capacitors c, and c,. A one mmf change
in either one results in approximately a

Fig. 4—The oscillator components are mounted ona sub-assembly panel along with other com-
pone y} g
ponents. The top of the panel is shown above and the back at the bottom.

half-cycle change in frequency. Since the
maximum possible change in capacitance
due to the tolerance of c, and c, is approxi-
mately 5 mmf, a maximum change in fre-
quency of 2.5 cycles is possible. Capacitor
c, is less critical than c, and c,; it requires
a 10 per cent change to produce a 0.3-
cycle change in frequency.

Plate and screen filter circuits are pro-
vided by rR, and c,, and rR, and c,; these
have negligible effect on the frequency of
oscillation. Resistor R,, is inserted in series
with the control grid to prevent spurious
oscillations at a frequency of approximately
200 megacycles. Variation in frequency
due to variations in the tubes is less than
half a cycle, and a 10 per cent change in
plate voltage also has negligible effect on
the frequency. A change in screen voltage
has little elect on the frequency but does
give a relatively large change in oscillator
output power. Since power for the repeaters
is furnished over the cable, and its voltage
changes with variations in cable resistance
due to temperature, the screen voltage is
obtained from the regulated voltage pro-
vided for the heaters of the tubes.

Crystals used in the repeater oscillators
have a variation with temperature as shown
in Figure 3. Frequency accuracy, as meas-
ured in a crystal test set, is specified
+0.007 per cent over a temperature change
ree —10 degrees to -+-50 degrees C (14-

122 degrees F). This includes, besides the
variation with temperatures, the accuracy
(£0.003 per cent) to which the crystal is
manufactured. To obtain a symmetrical
plus or minus tolerance, it is necessary to
adjust the frequency of the crystal, at room

temperature, about 8 cycles above the
nominal frequency. This is because the
change in frequency at the lower tempera-
tures is greater than at the higher tem-
peratures. This value is called the “offset”
frequency.

The temperature range over which the
repeaters must operate is —10 degrees to
+-60 degrees C (14 to 140 degrees F ). Over
this range, frequency variations of +10 cy-
cles can be expected. Added to the manu-
facturing accuracy previously mentioned
( +0.003 per cent, or +9 cycles), the total
crystal accuracy is +19 cycles. This means
that at room te mpe rature the crystal fre-
quency may be 304,008 +9 cycles, but over
the entire temperature range it will be
304,000 +19 cycles. Tolerances in circuit
components will add a maximum of +3
cycles; hence the repeater oscillator fre-
quency will have an over-all variation of
+22 cycles —which is within the design
objective of +25 cycles.

Group carrier oscillators are identical in
design to the 304 ke repeater oscillators ex-
cept for minor changes in circuit compo-
nents necessary for operation on stable
central office battery. The channel carrier
oscillator is similar in design to the re-
peater carrier oscillator, and utilizes the
same types of components. Since Type-N
terminals are located in heated central of-
fices, the temperature range is not so large
as that for the repeater carrier oscillator.
The circuit for all twelve channels is the
same except that the required frequencies
are obtained by using the appropriate crys-
tal. No suppression of harmonics is required
for channel use.

THE AUTHOR: J. |. De Buske received his B.S.
in F.E. degree from Newark College of Engineer-
ing in 1941. As a technical assistant in the Systems
Development Department, while attending Newark
College Evening School, he was engaged in the
testing and maintenance of laboratory test equip-
ment. In 1941 he was assigned to engineering of
repeaters for carrier systems, and in 1943 became
a Member of the Technical Staff. During World
War II, he worked on microwave radio telephone
systems and radar for the Armed Forces. Since the
war, his activities have been concerned with short-
haul carrier-telephone systems.

An electronic device that can understand
and intelligently react to spoken numbers
has been built at the Laboratories. Named
“Audrey,” which is a contraction of “auto-
matic digit recognizer,” it is a special cir-
cuit that can automatically determine which
of ten numbers, from 1 through 0, has been
spoken into a telephone.

An electronic telephone device which can under-
stand and intelligently react to spoken numbers is
put through its paces by K. H. Davis. “Audrey,” as
the device is known, has a special circuit which
automatically determines which of ten numbers has
been spoken into an ordinary telephone, and flashes
an appropriate light.

In its present form, the device responds
by flashing an appropriate light, but it
may equally well control other operations,
such as dialing mechanisms. Ultimately it
is hoped to extend the device’s vocabulary
to include additional sounds — words other
than numbers — and it is expected that the
device may even be taught to say some
words on command.

The newly constructed recognizer oper-
ates on a principle of memory and match-

ing. It listens to the human voice, then
sorts the speech sounds into electrical cate-
gories that conform in their own medium
to sound wave patterns. These categories
are analyzed by matching against a mem-
ory cell containing standard reference pat-
terns already set up electronically. When
the standard pattern is found which best
matches the electrical pattern of the spoken
number, the appropriate light flashes on.
When the device is adjusted for best per-
formance with a particular speaker, it op-
erates with high accuracy, but it is not yet
in a state to answer reliably to a wide vari-
ety of talkers unless it is readjusted for
each one. It will not tolerate careless enun-
ciations or accents.

The automatic recognizer is the subject
of a technical paper, published in the
November, 1952, issue of the Journal of the
Acoustical Society of America, by K. H.
Davis, R. Biddulph, and S. Balaskel. A
technical article will also be published in
a forthcoming issue of the Recorp.

During December, three links were added
to the Bell Telephone System’s nation-wide
radio relay network, providing expanded
facilities for telephone message and tele-
vision service. An additional westbound
channel has been placed in service between
Chicago and the West Coast on the trans-
continental route. This channel parallels
existing radio relay facilities, which are
routed to the Coast by way of Omaha and
Salt Lake City.

On the Pacific Coast, two additional
channels have been opened, one north-
bound and one southbound between Los
Angeles and the San Francisco area. The
northbound channel originates at Los An-
geles and it is routed to San Francisco via
Oakland. The southbound channel connects
Oakland with Los Angeles. Both of these
channels are joined to the transcontinental
group opened by the Bell System on August
17, 1951.

Although the computer of the AMA sys-
tem has many functions, the one from
which it derives its name, and its chief
one, is computing. The computing opera-
tions are all related to the determination of
charges for calls, and include: the calcula-
tion of the conversation time, the deduction
of a fixed allowance from the calculated
conversation time to compensate for re-
cording variations, the rounding off of the
net conversation time to whole minutes,
and, for calls that are to be bulk b'lled,
the conversion of chargeable time into mes-
sage units.

tion found in the three entries that the
computer receives for each completed
AMA call. From the answer entry and the
disconnect entry, the conversation time can
be calculated. After this conversation time
has been adjusted and rounded off, it be-
comes chargeable time. How this charge-
able time is used depends on whether the
‘all is a message-unit call or a toll call. This
information is contained in the initial entry.
Message-unit calls are rated by the com-
puter in terms of message units, and the
charges for all such calls are lumped to-
gether at subsequent stages of processing
and appear as one item on the subscriber's

“complements adding” process, which has
Tue Two-Our-or-Five tue been fully described previously’, is used
for calculating the conversation time.
In calculating conversation time, the
Decimal Two-out- Bi-Quinary Equivalent computer must also take into account the
Digit of-Five Bi Quinary passage of hours. Entries are recorded at
0 0 the beginning of each hour and are regis-
0 tered and checked by the computer as has
already been described+. To compute con-
versation time, it is necessary to know how
many hours have passed between answer
and disconnect times. The computer has an
“Hour Count” circuit which supplies this
information, and, after the answer time has
been subtracted from the disconnect time,

bill at the end of the month. Toll calls are Tas ie I] — REPRESENTATIVE CHARGING PLANS IN
rated at a subsequent accounting stage Use IN THE Bett System
after the computer has determined the Initial a
chargeable time, and all of these calls will Charge Initial Charge Overtime
appear individually on the bill that is sent in Period in Period
to the customer. Billing Message in Message in

A diagram of the computing operations — Formula Units Minutes Units | Minutes
is shown in Figure 1. The first step in the
computations is to translate the disconnect
and answer times from the “two-out-of-five”
code in which they were originally re-
corded to the “bi-quinary” code, which is
to be used for computing. The “two-out-of-
five” and “bi-quinary” codes are given in
Table I. Although there are many codes
available for use in computing, the “bi-
quinary” most nearly meets the require-
ments of the situation. These are: easy
translation to and from the “two-out-of-
five” code, which is employed in AMA,
vasy translation to and from the decimal
code for the convenience of accounting and
maintenance personnel who work with the an adjustment is made for the passage of
machine, relatively simple computing net- hours. Let, us assume a call that was an-
works, economy of apparatus—orly seven swered at 173 minutes after an hour and
elements are required to represent the ten disconnected at 35.7 mintites after an hour.
decimal digits—and the ability to be made Subtracting the answer time from the dis-
self checking. connect time gives a result of 18.4 minutes.

The computation of conversation time If the hour count shows that no change has
requires the subtraction of the answer time — taken place in the hour between the an-
from the disconnect time. Since both times swer and disconnect times, then 18.4 min-
are recorded in tens, units, and tenths of utes is the conversation time. If the hour
minutes after the last hour, this amounts to changes once, the answer being at 9:17.3
the subtraction of one three-digit number ~
from another. Although a direct subtraction

Recorp, December, 1946, page 457.
Recorp, July, 1952, page 289 and November,
operation might have been performed the 1952, page 422.

and the disconnect at 10:35.7, for example,
then sixty minutes must be added to get the
conversation time of 78.4 minutes. Simi-
larly, if the answer had been at 8:17.3 and
the disconnect still at 10:35.7, the hour
would have changed twice, i.e., from 8 to 9
and then from 9 to 10, and 120 minutes
must be added to get the conversation
time of 138.4 minutes.

After the conversation time has been
calculated, a small time allowance is made
to cover any delay that might have oc-
curred at the central office between the
actual disconnect and its recording on the
tape. The conversation time adjusted in this
manner is then rounded to whole minutes.
With an allowance of 0.1 minute, a call
with conversation time of 18.4 minutes
would fall in the interval 18-19 minutes
(designated by 19) while a call with con-
versation time of 18.1 minutes would fall
in the interval 17-18 minutes (designated
by 18).

The subsequent treatment of this charge-
able time depends on the message billing
index, which was registered as part of the
initial entry. If the billing index indicates
that the call is a toll call, the chargeable
time is registered and the computing op-
eration is completed for the call, since the
charges will be determined at a later time.
If, however, the billing index indicates that
the call is of the bulk billed variety, mes-
sage unit charges must now be computed
according to the billing formula designated
by the billing index.

There are many billing formulas in use
throughout the Bell System, and the con-
version of chargeable time to message units
depends on which billing formula applies
to the particular call. Each formula speci-
fies an initial time interval and the charge
in message units for this interval, and also
the length of and the charge for the over-
time interval. Some typical billing formu-
las are listed in Table If. The message-unit
charge for each length of chargeable time
from zero to thirty minutes for eight of
these billing formulas is given in Table III.
If a call lasted for fourteen minutes, for
example, and billing formula C applied,
the charge would be five message units.

units applicable to each call, the computer
employs circuits that are equivalent to a
set of tables, like Table III, but with a
chargeable time running from zero to
ninety-nine minutes. Calls which _ last
longer than ninety-nine minutes or for
which the charge is more than ninety-nine
message units are recorded on a special out-
put tape and are rated manually.

The circuit for converting chargeable
time to message units may employ any
number of billing formulas up to a total of
eight. Although there are many more than
eight formulas employed in the Bell Sys-
tem, there will not ordinarily be more than

Fig. 2—Simplified schematic of the circuit that con-
verts from chargeable time to message units,

groups of relays: one group representing
the tens digit, and the other, the units digit.
Leads from the contacts of these relays to-
gether with leads from the register for
the message billing index run to the con-
version circuit as indicated in Figure 1.
At the output of the conversion circuit there
are twenty message unit relays—ten for the
units digit and ten for the tens digit. The
function of the conversion circuit is to op-
erate the proper tens and units message
unit relays to give the number of message
units corresponding to the chargeable time
and the message billing index.

A diagrammatic over-all view of this con-
version circuit is given in Figure 2. There
is a cp relay corresponding to each billing
formula for which the computer is equip-
ped, and each relay is operated over one of
the eight leads from the message billing in-
dex register. The operation of the cp relay
connects the ten tens leads from the charge-
able time register to a group of Ta and 1B
relays. As shown in greater detail in Fig-
ure 3 there is a TA and a TB relay for each

Fig. 3—Schematic showing the arrangement of the
Ta and tp relays associated with each cp relay.

of the ten tens leads coming from each cp
relay, but for the sake of simplicity Fig-
ure 3 shows only the ta and 1p relays as-
sociated with one cp relay.

Each units digit in the chargeable time
register is represented by ground on two
leads. There are thus two groups of ten
leads for the units digit of chargeable time,
and one lead in each group will be
grounded for any one units value of charge-
able time. One of the groups of leads mul-
tiples to springs on all the va relays, and the
other, to springs on all the TB relays. The
front contacts of the Ta and TB relays con-
nect respectively to the windings of the
units and tens message-unit relays, Figure 2,
in accordance with the billing formula rep-
resented by the cre relay with which the
particular Ta and rp relays are associated.

When a cp relay is operated, the ground
on one of the tens digit leads of the charge-
able time register will operate the corre-
spondingly numbered ta and ‘rp relays in

series. As a result of the operation of a TA
relay, the ground on one of the units digit
leads from the chargeable time register will
be connected through to one of the message-
unit units relays, while as a result of the
operation of the 1B relay, ground will ap-
pear on one of the message-unit tens relays.
Figure 4 shows the circuit involved when
the cp relay number 3, corresponding to
billing formula D, is operated and when the
tens digit of chargeable time is one. Had
the tens digit of the chargeable time been
other than one, a different pair of Ta and
1B relays would have been operated. A
similar circuit is controlled by each of the
seven other cp relays.

It will be noticed that Figure 4 corre-
sponds to the parts of two columns of Table
Ill set in bold face type; it covers all
message-unit charges for formula D when
the tens digit of the chargeable time is one.
Contacts 10 to 17, inclusive, of the TB relay
are all multiplied together and connected

to the “zero” message-unit tens lead, while
the 18 and 19 contacts connect to the “one”
message-unit tens lead. Contacts of the Ta
relay are multiplied in pairs; contacts 10
and 11 connect to the number six message-
unit units relay; contacts 12 and 13, to the
number seven message-unit units relay, ete.

The fully equipped conversion circuit cor-
responds to a table, like Table IIT, extending
to ninety-nine minutes of chargeable time.
Each of the cp relays corresponds to one
of the eight lettered columns, and each pair
of ra and 1B relays associated with a cp
relay, correspond to ten lines of the column.

When chargeable time has been con-
verted to message units, the computing func-
tions are completed. The total time re-

THE AUTHOR: Since joining the Laboratories in
1945, Mary E. Pitviop has concerned with
AMA development, primarily the circuit design
and laboratory testing of accounting center ma-
chines used in this system, She participated in
pre-cutover tests of nationwide subscriber dialing
in Newark and Englewood in 1951, in accuracy
tests in 1948 at Philadelphia, where the first No. 5
installation with AMA was made, and a year later
in similar tests when No.
were used together for the first time. Miss Pilliod
has helped the American Telephone and Telegraph
Company prepare training and instruction ma-
me for use by the associated companies in oper-
ating AMA accounting centers. She was graduated
from Vassar College in 1945 with an A.B. degree.

quired to make the computations for the
call is approximately one tenth of a second.
This time, small though it is, includes
time to check at each step of the compu-
tations that the required result has been ob-
tained. Checks are made throughout the
entire AMA system, but they are nowhere
more important than here where the actual
charges for cills are calculated. The proof
of the efficiency of the checks is the fact
that from July, 1949 to March, 1951, almost
two years of AMA operation, during which
time more than 100 million calls were proc-
essed by AMA computers, there was no
known case of a call being wrongly charged
due to misoperation of any of the com-
puting circuits described in this article.

Each year, the A T & T Co. issues a re-
port on “Telephone Statistics of the World.”
The information, which takes almost a year
to collect from more than 250 governments
and companies throughout the world, shows
that during 1951, 4,600,000 telephones were
added throughout the world, bringing the
total in service on January 1, 1952, to 79,-
400,000. More than half of the increase
was in the United States where there was
a telephone for one out of every three per-
sons. Outside of this country, one out of
68 persons has a telephone.

New York City, with 3,349,323 telephones
on January 1, 1952, had more than any
other city in the world, more than all of
France, or the whole continent of Asia.

Greater London, with 1,710,000, was high-
est among foreign cities. Washington, D. C.,
had the greatest density of telephones, with
about 64 for every 100 persons. Atlantic
City was second with nearly 55, and San
Francisco was third, with about 54. The
foreign city reporting the greatest telephone
saturation was Stockho)m with almost 50
telephones per 100 persons. Canadians av-
eraged 378 telephone conversations per
person during 1951, the highest per capita
usage reported. The United States ranked
second with approximately 376 conversa-
tions and Sweden was third with about 309.

Besides the Bell System, comprising the
A T & T and twenty principal Bell Tele-
phone Companies, telephone service in the
United States was provided by nearly 5,500
other privately-owned telephone companies.

One of the many problems that plague
transmission engineers is that of obtaining
accurate measurements of inductance as the
frequencies used for communication go
higher and higher. Although measurements
at audio frequencies may readily be made
with bridges that have been in use for many
years, these bridges are not suitable for the
frequencies that have come into use in car-
rier and radio circuits within the past ten or
fifteen years. This is because the effect of
the parasitic capacitances and inductances
in the elements that make up the bridge, and
even in the connecting leads, impair the
bridge performance more and more as the
frequencies become higher and higher.

A direct reading inductance bridge that
vields accuracies comparable to those of
audio frequency bridges (of the order of 0.3
per cent) has been developed for use at

megacycle frequencies. Basically, the circuit
is that of a Maxwell bridge, shown in simpli-
fied schematic form in Figure 2. The product
arms Bc and ap contain the fixed resistors.
The standards arm aB contains an ad-
justable capacitor in parallel with an ad-
justable resistor, and the unknown imped-
ance is connected across the test arm cp. A
transformer across the diagonal corners
ac connects to the detector.

In the simplified schematic, Figure 2, the
fixed arms R,; and Ro are shown as pure re-
sistors; that is, they are assumed to have no
capacitance or inductance, and hence the
phase angle of each is zero. In the actual
construction of a resistor, it is difficult to ob-
tain this purity, because there is always
present some inherent distributed induct-

tively low dielectric constant (about 2). The
advantages of this construction are two-fold:
The skin effect is negligible, and the dis-
tributed inductance and capacitance are at
a minimum, thus producing an almost pure
resistor.

For the most practical design, the detector
transformer is connected so that the inner

ance and capacitance. Because of these char-
acteristics, when such a resistor is used on
alternating current, it becomes a complex
impedance. Besides, at high frequencies a
change in the magnitude of the resistance
also takes place due to “skin effect,” the ten-
dency of the current to flow chiefly along
the periphery of the conductor because of
the magnetic field set up by the current in
the conductor itself. These effects tend to
introduce a non-linear phase angle and vari-
able effective resistance, the magnitudes of
which depend upon the frequency, size of
wire, and the type of winding used.

To minimize these effects, and still main-
tain the required area of conductor surface
for heat dissipation, each of the fixed-arm
resistors for the new bridge consists of six
very fine wire-woven® units connected in
parallel and mounted on a Teflon spool.
Teflon is a solid dielectric having a rela-

shield capacitance falls across the ap arm of
the bridge. This arm, therefore, actually con-
sists of a low “Q,” two-element network in
the form of a lumped resistance in parallel
with a lumped capacitance. This is com-
pensated in the sc arm by connecting a
lumped inductance wound of stranded wire
in series with the resistor. The arms Bc and
ap thus contain inverse networks; that is, the
phase angles of the product arms Bc and ap
are, at all frequencies, equal in magnitude
and opposite in sign, so that their sum is
always zero, This scheme of compensation,
together with the shielding arrangement is
shown in the complete schematic of Figure 3.

Similar refinements were also made in the
adjustable arm of the bridge. Capacitance
standard c, is an air capacitor of a commer-
cial design, but provided with improvements
to make possible very accurate settings. A
cast metal frame gives it the necessary rigid-
ity, and a spring loaded worm drive is used
for setting the capacitor precisely and with

no back lash. Electrical connection to the
rotor is made by a brush that makes contact
with a disc located half way up on the
rotor shaft. With the connection to the
stator also at the mid-point, this capacitor
is equivalent to two capacitors in parallel,
and the series inductance and metallic re-
sistance are only about one fourth those of
a similar capacitor having the take-off ter-
minals at the end. In addition, the a and B
bridge corners (Figure 3) are located on the
capacitor stator and rotor take-off terminals,
thus eliminating leads and minimizing series
resistance and inductance.

Conductance standard cG,, Figure 3, con-
sists of resistors that are controlled by three
rotor decade switches and a continuously
adjustable dial. Each decade switch and the
continuously adjustable resistor are con-
nected independently to the a and B corners
of the bridge by short rigid leads.

A developed diagram of a rotor switch is
shown in Figure 4. The switch is essentially
an eleven position contact wafer and an
eleven position short-circuiting wafer, both
mounted on a common shaft. As indicated
in the figure, the shorting wafer connects all
the switch terminals except one to the B
corner of the bridge when the shaft is in a

capacitor. Each resistor has a different re-
sistance value, so as to obtain the desired
decade range, and each trimmer capacitor
is adjusted so that all resistors, with their
associated contacts and wiring, have the
same effective residual capacitance. As the
contact arm of a decade switch is moved,
only one resistor unit and its associated
capacitor is in the circuit at one time, while
all the remaining units are short circuited to
the B corner. Since the effective residual
capacitance is adjusted to be the same re-
gardless of the setting of the decade, this
capacitance is considered as a part of the
standard capacitor residual capacitance, and
the decade switching arrangements are thus
equivalent to pure conductances.

The resistors used on the decade switches
are physically alike and of the hermetically
sealed deposited carbon type®, in order to
assure maximum stability, small distributed
capacitance, and low skin effect. The re-
sistor used with the continuously adjustable
dial consists of a hermetically sealed carbon
resistor in series with a slide wire that is
wound non-inductively and mounted on a
molded insulating drum so as to have mini-
mum capacitance to the shield.

Fig. 4—A developed circuit of the decade conductances. Rotor switches connect all resistance-
capacitance networks to ground except one, for each position of the decade dial.

given position in order to avoid parasitics
through the unused resistors. The contact
wafer makes connection with only the one
unshorted terminal at the same time. Be-
tween each switch terminal and the B corner
are connected a resistor and a small trimmer
capacitor in parallel, except for number
zero, which fea only the small trimmer

down to zero impedance across the test ter-
minals, a shielded coil, indicated in Figure
2 as lo, and ro, is connected between the c
corner and the x, terminal. This coil is ten-
sion wound on a form having a low tempera-
ture coefficient of expansion, in order to

maintain maximum stability of impedance.
Its impedance is equivalent to the residuals
of the capacitance and conductance stand-
ard as reflected through the fixed arms of
the bridge. In addition, the x, terminal is of
small physical dimensions to minimize the
effect of capacitance to ground across the
unknown impedance. The arrangement of
these component parts is shown in Figure 1.

A front view of the bridge is shown in
Figure 5. Terminals x, and x,, for connect-
ing the unknown, are located in the upper
left-hand corner, remote from the bridge
dials in order to minimize the effect of hand
capacitance of the operator. Since this bridge

is designed to be direct reading, the con-
ductance dials are engraved to read ons,
and the capacitance dial is engraved to read
pat (microhenries ). Two dials in the lowest
row, marked Lo and Ro, serve to establish a
bridge zero balance when all the standard
dials are set to zero, and the bridge termi-
nals x, and x, are short circuited.

The dial in the lower right-hand corner
marked onm, and having steps of 0.02, 0.01
and 0.005 serves to introduce additional frac-
tional resistance above the “10” setting of the
0.01 ohm dial, or the “11” setting of the 0.001
ohm dial in the middle row. This facilitates
bridge balancing by avoiding resetting these
dials to the next higher decade when only a
small increment is required.

Impedance measurements can be made
at frequencies as high as 5 megacycles,
with inductances up to 10 microhenries
and resistances up to 11 ohms. Minimum
steps of 0.0005 microhenries (% division on
the vernier dial) are possible, as well as re-
sistance steps of 0.00005 ohm (% division on
the 0.001 ohm continuously adjustable dial).

The bridge is direct reading, and requires
no calibration corrections. It is now being
used in the inductor laboratory in connec-
tion with the development of component
parts of transmission networks for mega-
cycle carrier systems.

THE AUTHOR: L. E. Hersorn joined the Tech-
nical Staff of the Laboratories in 1923, and until
1928 was associated with the Research Department
on the development of terminal equipment for
high-speed submarine cables. At the completion
of this work he transferred to the Apparatus De-
velopment Department, where he engaged in the
development of precision impedance measuring
equipment. During the war he collaborated in
development of circuits for military equipment.
Mr. Herborn has the degree of B.S. in E.E. from
Cooper Union.

Editorial Note: Common control switching
circuits and the various forms of electrical
computers operating on similar principles
have often been referred to as electrical
brains because of the distinctly rational
operations they are able to carry out. To
just what extent the actions of the human
brain can be duplicated by electrical cir-
cuits is still a moot question. Some members
of the Laboratories feel that probably no
switching circuit could duplicate all the
acts of the mind, while others feel that it is

Can the functions of the human brain
be reproduced by switching systems? This
subject has been thought about lately by
many people, inside and outside Bell Tele-
phone Laboratories. It is a loose and con-
troversial (but fascinating) subject whose
~ “The Thinker,” the »hotograph at the right, by
Auguste Rodin, is published through the courtesy

at least theoretically possible to design a
group of electrical circuits that would dupli-
cate many functions of the human brain.
John Meszar gives here a brief outline of
one position. It is intended that other views
on this question will eventually be pub-
lished in forthcoming issues. The question
is one of such general interest that Bex.
Lasoratories Recorp feels it worthwhile
to present these differing opinions although
recognizing that at the present time they
are opinions — not established facts.

ramifications quickly bring into play dif-
ferent interpretations of the human mental
process, most of which are based — like
this article — on opinions and speculations
rather than facts. It is also a subject which
can be discussed casually as the weather,
or pursued doggedly at the risk of one’s
peace of mind. Best of all, one does not
have to know a great deal about switching

To establish requested con-
nections, automatic  tele-
phone switching systems
accurately link-up appro-
priate sections of a maze
of paths.

systems to feel the equal of experts in ap-
praising them as mechanized brains.

Let us be a little more explicit about the
subject. As is well known, the most funda-
mental characteristics of the switching art
—the characteristic responsible even for
the name of the art—is its use of the
“switch,” an elementary two-valued (open
or close) device, and corresponding two-
valued (on or off) signals. Based on these
elementary devices and signals, switching
systems have been conceived and brought
into existence which can receive a lot of
information, and manipulate it automatic-
ally through a sequence of internal steps
until some predetermined final objective is
accomplished. To telephone engineers, the
best known example of such a system is, of
course, the common-control dial telephone
switching system which receives from thou-
sands of subscribers information specifying
the telephone they want to be connected
with, and which accurately links up the ap-
propriate sections of a maze of paths to es-
tablish these requested connections. Out-
side of the telephone field, it is the auto-
matic digital computing systems, such as
the ENIAC, UNIVAC, and ORDVAC, that
recei\. the most attention as switching sys-
tems of truly significant capabilities. With
appropriate instructions they can, for in-
stance, calculate the trajectory of a gun
shell faster than the shell can fly it.

From the standpoint of this article, the
chief item of interest about any of these
systems is that in accomplishing the over-all
objective of the system, its component cir-
cuits perform such functions as: counting,
remembering, selecting, deciding, translat-
ing, locating, and calculation — functions
that strongly imply operations commonly
associated with human mental effort. This
then brings up the natural question: Are
such implications justified and _ significant,
or are they simply the result of poetic li-
cense in the use of words by switching peo-
ple? In other words, do switching circuits
truly reproduce certain processes of the
human mind or, like costume jewelry, are
they but superficial imitations that do not
stand critical examination? The question
becomes even more appropriate in the
light of the limited knowledge that neuro-

physiologists are acquiring of the human
brain's own internal processes, which
seems to indicate that —like a switching
system —the brain also accomplishes its
functions by internal rearrangements of its
superlative network of two-valued ele-
ments, the neurons.

Before anyone gets the impression that
this article is going to be a dissertation on
“machines that think,” that anticipation
will be disposed of forthwith. The subject
of “thinking machines” receives more than
its just share of attention in articles of those
writers who extract the last ounce of specu-
lative excitement out of it. One such arti-
cle in a respectable weekly magazine, for
instance, noted that during the post-war
peaks of telephone traffic certain crossbar
central offices misbehaved in a manner that
baffled the engineers. Since a working cross-
bar office depends on the dynamic inter-
play of thousands of relays, such a situation
was not surprising to those of us who have
often been puzzled by the misbehavior of a
single complicated switching circuit dur-
ing laboratory tests. The subtle implica-
tion conveyed by the article, however, was
that such systems therefore have character-
istics akin to capricious will. In fact it is
not doing much injustice to the article to
infer that some day Telephone Companies
might decide to hire psychoanalysts to help
switchmen maintain crossbar central offices.
Such views about machines that think and
act according to their thoughts are intui-
tively repugnant to most of us.

It is appreciated that this assertion is
subject to quick retort along the lines that
intuitive feelings can be wrong. There was
a time, for instance, when it was also
against common sense to admit that the
earth is round, not flat, and that it is wan-
dering as a speck in the universe, rather
than Seis its center. Ancient, deep-rooted
concepts are not readily changed even if
ultimately they prove to be wrong. How-
ever, on mechanical thinking we can but-
tress our intuition by tangible, factual sup-
ports. We know that an automatic system is
but hardware, shaped of steel, and copper,
and glass, and other dead materials. Such
materials can move, expand, and contract
in response to forces; some can be mag-

netized; some can transmit electrical energy
and so on; but these properties do not even
remotely resemble the ability to think,
which is the highest, most exclusive en-
dowment of the living human mind. Design
engineers who have brought into existence
such outstanding examples of automatic
systems as our modern common-control
central-office systems know best how pro-

The operator functions as a highly intelligent and
versatile switching system.

saic is the hardware employed, and how
common-place are the details that make
such systems tick.

This answer to the basic question looks—
and is—arbitrary. If the question of
mechanized thinking could be disposed of

that easily, this article would stop right
here; in fact it would not even have been
started. There is much more to the subject.
Just what do we mean by thinking? What
operations of the human mind come under
this term? Let’s discuss a few elementary
examples that may confirm the doubts of
those not sure of the answer, and may cre-
ate doubt in those who feel they know the
answer.

Someone requests the Laboratories’ tele-
phone operator for a connection to exten-
sion 752. The operator makes a busy-test,
receives an indication that the extension is
in use, and therefore refuses to comply
with the request. In so doing, did she use
her head? She certainly did and her super-
visor would unhesitatingly agree. Testing
for and respecting a busy line, however,
is also one of the simplest accomplishments
of an automatic switching system.

At the switchboard of a manual exchange,
the operator receives a call for line No.
4700. She promptly locates the jack ter-
minating this line, and is set to make a busy-
test. However, she notices a distinctive
mark at this jack, indicating that 4700 is a
line to a Private Branch Exchange, which
is served by a multiplicity of adjacent lines,
all usable when 4700 is called. If the first
of these lines is busy, therefore, she does
not turn down the request for connection.
Instead, she hunts in an orderly manner
for an idle line in the 4700 group. Did the
operator go through some mental process
in this short sequence of actions? One
would be reluctant to say no. However,
locating the physical termination of a sub-
scriber line, noticing that it’s a PBX line,
and hunting for an idle one in the group,
is one of the many features of dial telephone
system circuits.

A conventional problem in telephone mes-
sage accounting may involve the follow-
ing charging plan: initial conversation
interval of five minutes chargeable at three
message units; overtime conversation in-
tervals of two minutes, each chargeable at
one message unit; a very short (say six
seconds ) deductible allowance on all mes-
sages. Now, an operator's ticket shows that
a certain telephone conversation started at
58.6 minutes after 2:00 P.M. and ended at
25.8 minutes after 3:00 P.M. If the message-
rater of the accounting center bills the
customer fifteen message units, did she do
any thinking in arriving at this answer?
Not many will deny it. However, that is ex-
actly what one of the automatic message
accounting machines accomplishes.

After some minutes of calculations on paper
(with indications of erasures, perhaps) he
comes up with the correct answer. In doing
this problem, did he go through a process
of thinking? Most everbody will unhesi-
tatingly — and perhaps unwarily — answer
yes. Some would even compliment them-
selves silently for good mental perform-
ance if they went through all the steps of
the problem in a number of minutes and
obtained the correct answer. However, a
digital computer will also give the correct
answer and do so in a split second.

So much for elementary examples of hu-
man mental operations which are repro-
duced exactly by switching circuits. A
whole series of other examples could be
readily cited. None of these examples is
impressive by itself, but a switching sys-
tem may include a great many such simple
features, and the resultant versatility of the
system, its composite competence to per-
form a relatively complex series of mental
operations, may therefore be truly remark-
able. Thus the question: What is thinking?
is very much in order. Is mental effort the
same as thinking?

If we do not want to be trapped into ad-
mitting that automatic systems think, we

can give only one answer to the question.
We do not think every time we use our
head. Much of our mental effort consists
of recalling facts stored in our minds (the
multiplication table, for example), and
manipulating such information in accord-
ance with a set of rigid rules, also stored
in our minds. The facts and the rules of
manipulation have been implanted in our
minds some time or other as part of our
training, and are treated as inviolate, un-
alterable. Mathematical computations —
be they simple or intricate —are typical
examples of this type of mental effort. The
simple multiplication problem used above

A switching system is a se sar structure of relays,
tubes, wires, etc., combined with a wealth of stored
information.

and they would all use the same mentally 4
stored information, and follow an identical

Mathematical computations are, how-
ever, not the only acts falling into the cate-
gory of “non-thinking mental effort.” Any
problem, any situation which demands the
exercise of rigorous logic, where the pro-
cedure and the final outcome is inherent in

Machines are taking over many areas of mental effort. Above, one of the machines of the auto-

the statement of the initial conditions,
where the “if then” relationship
holds, is of the same type. Solving such
problems, taking appropriate action in
such situations is mental effort, but it is not
thinking. Each new problem and situation
of this type calls simply for the reuse of the
same stored facts and the application of
the same rigorous rules of procedure to a
set of new variables to arrive at a new but
inherent conclusion. The facts and_ the
rules can be implanted into human minds
by training, or they can be incorporated
into automatic systems by design. For a
given set of initial variables they will both
go through identical steps and arrive at
the same answer.

Now the theme of this article has
emerged. It is an emphasis on the neces-
sity of divorcing certain mental operations
from the concept of thinking, and thus
pave the way for ready acceptance of the
viewpoint that automatic systems can ac-
complish many of the functions of the hu-
man brain. From this viewpoint, it is not
the physical structure of relays and tubes
of an automatic system that functions as

the brain. The mechanical brain is the
combination of that structure with all the
information it possesses. Such a loaded
structure, in certain areas of mental effort,
may even outperform the human brain. In
those areas, therefore, the analogy between
switching circuits and the human mind is
not that of imitation versus genuine jewelry,
but that of artificial crystals grown by the
Western Electric Company versus natural
crystals mined in South America. Perform-
ance, uniformity, and price are actually in
favor of the artificial ones.

Divorcing thinking from what we regard
at the present time as routine, logical men-
tal operations is not enough. As time goes
on, it will be more and more essential to
cultivate a completely undogmatic and
open-minded attitude for the concept of
thinking. Perhaps the most flexible concept
is that any mental process which can be
adequately reproduced by automatic sys-
tems is not thinking. There are several
basic virtues in this flexible concept. First,
it avoids the extremely difficult, if not im-
possible task, of defining positively what
thinking is, by stating what is not thinking.

Second, it is easy to apply and results in
straightforward conclusions. Once a ma-
chine performs a certain type of mental
operation, that operation is not thinking.
Third, it makes full allowance for the in-
creasingly versatile automatic systems of
the future, which are unquestionably com-
ing and which will force an accelerated
shrinkage in the area of mental effort to
which the term “thinking” remains ap-
plicable. It is well to recognize that in
time this shrinkage may become very
extensive as switching systems come into
existence to perform more and more spec-
tacular feats of logic, such as automatic
weather predicting, automatic language
translating, etc.

We are faced with a basic dilemma; we
are forced either to admit the possibility
of mechanized thinking, or to restrict in-
creasingly our concept of thinking. How-
ever, as is apparent from this article, many
of us do not find it hard to make the choice.
The choice is to reject the possibility of
mechanized thinking but to admit readily
the necessity for an orderly declassification

of many areas of mental effort from the
high level of thinking. Machines will take
over such areas, whether we like it or not.

This declassification of wide areas of
mental effort should not dismay any one
of us. It is not an important gain for those
who are sure that even as machines have
displaced muscles, they will also take over
the functions of the “brain.” Neither is it
a real loss for those who feel that there is
something hallowed about all functions
of the human mind. What we are giving up
to the machines — some of us gladly, others
reluctantly —are the uninteresting flat
lands of routine mental chores, tasks that
have to be performed according to rigor-
ous rules. The areas we are holding un-
challenged are the dominating heights of
creative mental effort, which comprise the
ability to speculate, to invent, to imagine,
to philosophize, to dream better ways for
tomorrow than exist today. These are the
mental activities for which rigorous rules
cannot be formulated — they constitute real
thinking, whose mechanization most of us
cannot conceive.

THE AUTHOR; Meszar was graduated
from Cooper Union in 1927 with a B.S. degree in
E.E. He has been employed by the Laboratories
since 1922 when he began work as a technical
assistant working on the testing of toll switching
circuits. In 1942, after several years as a super-
vising engineer in toll switching circuit design
work, he sell an instructor in the Laboratories’
School for War Training. Following the war, he
returned to circuit design supervision and devoted
much of his time to AMA. Since June, 1952, he
has been Director of Switching Systems Develop-
ment II. In 1951 the American Institute of Elec-
trical Engineers awarded him first prize for the
best paper in the communication division pre-
uring 1950,

One of the most interesting aspects of
electrical insulators is how they conduct
electricity. Although by definition they
are non-conductors, it is well known that
under the proper circumstances they will
conduct. It was demonstrated over seventy-
five years ago that light shining on certain
insulators could render them slightly con-
ducting. However, it is only within the
past decade that it has been shown that
comparatively large currents could be pro-
duced in certain insulators by bombarding
them with high speed particles of atomic
size. The particles liberate charge carriers
within the insulator, and these may move
if an electric field is applied.* By studying
the behavior of these induced currents we
can extend our knowledge of the electrical
properties of solids and can also study

* In this study we are not dealing with per-
manent changes produced by the bombarding par-
ticles. The induced currents in general cease when
the bombardment is terminated or very shortly
thereafter.

what happens when a solid body is struck
by a high speed particle, such as alpha par-
ticles that are emitted during radioactive
decay, or high speed electrons, such as ex-
ist in a beam of a large TV tube.

This is not as academic as it sounds. If
a high speed particle can produce mobile
charges in an insulator which can then
be measured, a method of detecting particles
becomes available; this is of considerable
interest to nuclear physicists. Moreover the
action of solid-state devices, such as va-
ristors, or transistors, depends on electrical
conduction through non-metallic solids. If
the physics involved is well understood, it
will certainly be used eventually in de-
vices. Conductivity induced by bombard-
ment is one of the tools at our disposal to
study the underlying physics. In the fol-
lowing pages is a brief résumé of the basic
processes and some of the information that
has been gleaned from the studies at Bell
Telephone Laboratories.

THE ALPHA PARTICLE STRIKES
THE CRYSTAL PRODUCING A
DENSE CYLINDER OF MOBILE
POSITIVE HOLES AND ELECTRONS

UNDER THE INFLUENCE OF THE
APPLIED ELECTRIC FIELD, POSI-
TIVE HOLES MOVE TOWARDS
THE NEGATIVE ELECTRODE ANDO
ELECTRONS MOVE TOWARDS THE
POSITIVE ELECTRODE

MANY CARRIERS HAVE REACHED
THE ELECTRODES; THE OTHERS
HAVE BEEN IMMOBILIZED IN
TRAPS. ALL MOVEMENT OF
CHARGE HAS STOPPED AND A
SPACE CHARGE FIELD iS
ESTABLISHED IN THE CRYSTAL

does not normally conduct electricity. To
be specific we shall consider the case of
diamond, which is a simple but excellent
insulator. Diamond is composed of nothing
but carbon atoms. The outermost group of
electrons of each atom act to hold the dif-
ferent atoms together. If there are just the

to roam through the crystal. However, these
free electrons are not the only current car-
riers. Another type of carrier arises because
the places formerly occupied by the free
electrons are now empty. In some crystals
like diamond, the electrons in neighboring
bonds (positions) can exchange places
with each other readily. If an electron in,
say position A, jumps into neighboring
position B where a bonding electron is
missing, there will no longer be an electron
in position A. This is the same as saying
that the vacancy has moved from B to A
and thus, in this case, is mobile. Since the
vacancy occurs in what is normally a neu-
tral crystal, it forms a region of positive
charge, and the fact that it is mobile per-
mits it to act as a charge carrier in a crys-
tal. Thus each significant collision made by
a bombarding particle produces both a
free electron and a positive hole. Under
the influence of an electric field, the elec-
tron moves off in one direction, the positive
hole moves off in the other direction, and

right number of these electrons present,
the atoms will be very tightly bound to-
gether, thus forming ‘the hard diamond
structure. It happens that each carbon
atom brings with it just the right number
of electrons to attach it strongly to its sur-
rounding atoms so there are no electrons
left over. Now if an electric field is applied
to the diamond, none of the atoms will
move appreciably, since they are all tightly
bound together. Moreover the electrons
are all occupied holding the atoms together,
and thus they cannot contribute to a cur-
rent flow. C vonseque ntly there is no current
flow. This is the simplest possible picture
of an insulator.

It appears reasonable that if some elec-
trons can be supplied which are not bound
to the atoms, then these should be able to
move more or less unimpeded through the
solid, and thus render it conducting. This
‘an be accomplished by shooting particles
such as high speed alphas into the insula-
tor. Practically all of the energy of the al-
phas will be dissipated in collisions with
the electrons which bind the atoms to-
gether. These collisions knock the erstwhile
bonding electrons loose, setting them free

Fig. 3—Variation of elec-
tron current through
crystal as a function of
applied voltage. This is
for a diamond crystal
bombarded by 10-kilo-

One of the first things we would like to
know is how the induced current should
vary with applied voltage, with the inten-
sity and the type of bombardment, and
with any other relevant variables such as
time. It is to be expected that a free charge
carrier will bounce around in the crystal
and drift in the direction of the applied
field with a velocity equal to the field times
a constant which is called the mobility. It
is also expected that in any actual crystal
likely to be used, there are local impe rfec-
tions that disrupt the symmetrical arrange-
ment of the atoms. These imperfections
might consist of foreign atoms (impurities )
or merely misplaced atoms of the crystal.
From experience it is known that these im-

Fig. 4—Electron current flow through a diamond as
a result of bombardment by a 10 ,-second pulse of
10-kilovolt electrons. The decrease in current near

4 the end of the pulse is caused by the formation of
an internal space charge field during the period of
the bombardment.

Fig. 5—Pulses from a diamond crystal bombarded by
monoenergetic alpha particles. Observe the scatter
in pulse heights due to nonuniform response.

Fig. 6—Plot of the counting efficiency in per cent of
a large flat diamond when bombarded by alpha par-
ticles. Such wide variations in sensitivity in different
parts of a diamond are usually encountered.

perfections may prove very attractive to
free carriers; a carrier drifts into the re-
gion around an imperfection, exchanges
energy with the surrounding atoms, and
then finds that it doesn’t have enough
energy to leave the region because of the
peculiar local electrical disturbance set up
by the imperfection — the carrier has been
trapped just as a billiard ball is pocketed.
The longer an untrapped carrier remains
free in the crystal, the more likely it is that
it will drift into such a region and be
trapped. At low field strengths, the carriers
drift more slowly and take longer to tra-
verse the crystal; trapping becomes more
effective and smaller currents may be ex-
pected. Moreover, the trapped carriers, by
virtue of their electrical charge, set up in-
ternal electric fields which oppose the ap-
plied field and cause the current to dimin-
ish with time. This is a nuisance but, for
measurement purposes, it can be avoided
by releasing the trapped charges by ap-
plying heat or light, or through the use of
ac fields in which on alternate half cycles,
positive holes are supplied by bombard-
ment, and these recombine with the
trapped electrons and vice versa. All three
methods have been successfully used and
thus it may be assumed from here on that
the crystals considered are free of space
charge unless otherwise stated.

To make actual measurements on a dia-
mond crystal, a thin slice, such as a seg-
ment cut off a gem stone prior to polishing,
is taken and the two major faces are coated
with thin metallic films, which serve as
electrodes. A voltage is applied between
the electrodes, and an amplifier and oscillo-
scope are connected to amplify and _re-
cord any current flow through the crystal
(Figure 2). The bombarding particles
penetrate one of the electrodes and dissipate
their, energy in the crystal. If alpha parti-
cles are used, the current pulses due to the
incidence of individual alpha particles are
studied. When electrons of about twenty
kilovolts energy are used the response to
individual electrons cannot be measured,
and so a pulsed beam of electrons is used.
The crystal is usually mounted in a vacuum
chamber to prevent the bombarding par-
ticles from losing energy to air molecules.

Bombardment by alpha particles or by
electrons produce essentially the same et-
fects although each emphasizes certain
properties of the target more effectively
chan the other: electrons are more suitable
for the study of the over-all electrical prop-
erties of the target while alpha particles
are singularly appropriate for the investi-
gation of crystal inhomogeneities. Experi-
ments show that both free electrons and
positive holes are mobile in diamond at
room temperture, and that the average
amount of energy required from the bom-
barding particle to produce one free elec-
tron and one positive hole in the crystal is
about ten electron volts. Thus a 20,000-volt
electron striking a diamond crystal will
produce about 2,000 electron-hole pairs.
In any particular crystal, it is possible,
by studying the observed relationship be-
tween the current and the applied voltage,
to make estimates of the density of the
traps, and to get some idea of the amount
of energy required to release a charge car-
rier once it has been trapped. This is the
kind of information necessary for future
theoretical studies. However, as will be
discussed below, such estimates must be
treated with caution unless there exists in-
dependent evidence that the electrical
properties of the crystal that is used are
fairly uniform.

In addition to these quantitative results,
the experiments have also forced us to
change our mental picture of the electrical
structure of many insulators. On at least
one selected diamond, very careful studies
were made of the dependence of induced
current on applied field and on the energy
of the bombarding electrons. Moreover,
after the internal space-charge fields had
been neutralized, they were allowed to
build up under controlled conditions, and
their rate of production was measured. The
results agreed very well with theoretical
predictions based on the assumption of a
uniform electric field throughout the crys-
tal and of a uniform distribution of traps.
This is a very satisfying result, but unfor-
tunately it is very rare.

If a diamond is bombarded with alpha
particles, each with the same energy, the
simple theory with the above assumptions

predicts that each resultant conductivity
pulse will be of the same height when seen
on an oscilloscope. Actually this is almost
never the case; the observed heights scat-
ter very widely. This implies that since the
different alphas enter different regions of
the crystal, these regions must iffer in
their electrical properties. For other rea-
sons it is believed that the variation occurs
in the conducting properties of the crystal
and not in the carrier excitation process.
The simplest explanation of this effect is
to postulate an inhomogeneous distribution
of traps so that one alpha particle strikes
a relatively trap-free region and the re-
sultant carriers travel a long distance before

Fig. 7—Sixteen superimposed pulses from alpha
particles striking a germanium n-p junction
shown on an expanded time scale. The very
fast rise time indicates that the electrons and
holes produced by the bombardment are swept
across the junction in a time less than 10°

being trapped, while the next alpha hits a
trap-rich region and the carriers are immo-
bilized before they can drift at all. Un-
doubtedly this is an important factor. How-
ever, the results of subsidiary measurements
on some diamonds indicate that variations
in trap density do not tell the full story. It
has become evident that even an excellent
insulator may possess more or less localized
regions of appreciable conductivity in the
absence of any bombardment. This means
that if a voltage were applied to a crystal
before any bombardment occurred, the
electric field might vary greatly within dif-
ferent parts of the crystal. Thus a region
that responds exceptionally well to bom-
bardment may be one in which the carriers
are produced in an exceptionally high local
field. G. H. Wannier has shown that the
introduction of an extremely small quan-
tity of impurities into a really good insu-

Fig. 8—Pulses from a germanium n-p junction bom-
barded by monoenergetic alpha particles. With a
few exceptions, most of the pulses are the same
height.

lator should, in theory, lead to just such a
result, and our experiments appear to con-
firm it.

Although this behavior holds for dia-
mond, does it for other insulators? A. J.
Ahearn has tested over a hundred different
species of insulators and found only seven
that yielded a measurable response to alpha
particle bombardment. All of these ex-
hibited wide distributions of pulse heights,
and thus so far there is no reason to expect
a different behavior. One annoying aspect
is that in those cases where the value of the
internal field is not known, many of the
measurements we would like to make can-
not be properly interpreted. Under high
field conditions, for example, trapping can
be neglected and, mobility ». is given
simply by

where | —-the distance between electrodes
7-—=the time taken for the electrons to
traverse the distance |

E =the electric field
This equation is applicable when the field
E is a constant, and since we can measure
r, Land E, we can determine ,,. However,
if E is not constant but varies in an un-
known manner, measurements of 7 are use-
less to determine pe.

and from that discussion it is evident that
a barrier layer, as set up by a point con-
tact or by an n-p junction, acts very much
like a thin layer of insulating material sepa-
rating two conductors if the proper volt-
age is applied. A high field can be estab-
lished across such a barrier and trapping
normally plays a negligible role. Although
bombardment conductivity studies have
been made on the barrier layers around
point contacts and on surface barrier layers
stabilized by chemical treatment both with
alpha particle and electron bombardment,
the clearest interpretations have been ob-
tained using n-p junctions. The number
of carriers produced per bombarding par-
ticle of a given energy is well defined, and
corresponds to the production of one elec-
tron-hole pair for every three electron-volts
energy of the bombarding particle. This
should be compared with the corresponding
figure of ten electron-volts per pair in dia-
mond and about thirty-five electron-volts
per electron-ion pair in air.

Although diamond and germanium ap-
pear at first glance to be dissimilar ele-
ments, this is not entirely true. They have
the same crystal structure, they are mem-
bers of the same chemical “family”, and
many of their properties are only quanti-
tatively different. Thus measurements on
one element, if properly interpreted, may
be very useful in predicting the behavior
of the other element. Bombardment studies
on germanium n-p-n junctions — the junc-
tion transistor structure — yield results of
the type to be expected in some insulators
as a result of peculiar internal field con-
figurations. This ties right back to Dr. Wan-
nier’s concept of the behavior of diamond.

From this discussion it is evident that
the use of bombardment conductivity has
proved fruitful in the study of the behavior
of electrons in certain types of solids. One
additional point to be noticed is that bom-
bardment conductivity is a means of pro-
ducing current multiplication; one high
speed electron bombards a crystal and
many free carriers are produced inside.
This property suggests possible applications
such as high speed electronic switching or

The work at the Laboratories which has
formed the basis for this article was initi-
ated by D. E. Woolridge. The alpha bom-
bardment and supplementary measure-
ments on insulators has been carried on by

A. J. Ahearn. We wish to acknowledge the
many contributions by other members of
the staff and, in particular, those of J. A.
Burton who, for a while, directed the work
in its early stages, and those of R. R.
Newton who calculated the rate of produc-
tion of internal space charge fields. The
technical assistance rendered by R. A.
Maher and H. C. Meier has been most valu-
able in these investigations.

THE AUTHOR; Since 1947 KennetuH G. McKay
has been conducting fundamental research on
electron bombardment conductivity in insulators
and semiconductors. Dr. McKay received B.Sc.
(1938) and M.Se. (1939) degrees from McGill
University and in 1941 an Sc.D. degree from
Massachusetts Institute of Technology. He then
joined the National Research Council in Canada
to work on the design of radar equipment. In
1942 he was commissioned in the Royal Canadian
Air Force and was assigned to duty with the re-
search council. He remained in service until 1946,
when he became a member of Bell Telephone
Laboratories. He developed pulse techniques for
the study of electron emission from insulators for
about a year, before going into the work that
he is now doing.

Anderson, J. R., Ferroelectric Storage Elements
for Digital Computers and Switching Systems.
Elec. Engg., 71, pp.916-922, Oct., 1952, and Com-
munications and Electronics, 4, pp.395-401, Jan.
1953.

Coy, J. A., and E. K. Van Tassel, Type-O Car-
rier Telephone. Communications and Electronics,
4, pp.428-437, Jan. 1953.

Keller, A. C., A New General-Purpose Relay for
Telephone Switching Systems. Communications
and Electronics, 4, pp.413-428, Jan., 1953.

Mason, W. P., Properties of a Tetragonal Anti-
ferroelectric Crystal. Phys. Rev., 88, pp.480-484,
Nov. 1, 1952.

Mason, W. P., and B. T. Matthias, Piezoelectric,
Dielectric, and Elastic Properties of ND,D.PO,
(Deuterated ADP). Phys. Rev., 88, pp.477-479,
Nov. 1, 1952.

Following is a list of the authors, titles, and place of publication of recent papers pub-

Olmstead, P. S., How to Detect the Type of an
Assignable Cause. Ind. Quality Control, 9, pp.32-
34, 36+, Nov., 1952.

Peterson, G. E., Application of Information
Theory to Research in Experimental Phonetics.
Jl. Speech and Hearing Disorders, 17, pp.175-188,
June, 1952.

Shockley, W., Interpretation of e/m Values for
Electrons in Crystals. Phys. Rev., 88, p.953, Nov.
15, 1952.

Wright, E. E., Stress Relaxation in Plastics and
Insulating Materials. A. S. T. M. Bull, 184,
pp-47-49, Sept., 1952.

During the month of December, a number of Laboratories people gave talks before
professional and educational groups. Following is a list of the speakers, titles, and place

Andrews, E. G., A Review of the Bell Labora-
tories Activities in Digital Computer Develop-
ments, A. I. E. E., Ithaca Section, Ithaca, N. Y.

Becker, J. A., The Field Emission Microscope
and Its Use in the Study of Chemisorption, Ca-
talysis Club, Philadelphia, Pa.

Chapman, A. G., How Crosstalk and Noise Af-
fect Capacitance Unbalance Requirements, Par-
ticularly in Spiral-Four Cables, Signal Corps Sym-
posium, Asbury Park, N. J.

Darrow, K. K., Magnetic Resonance, A. I. E. E.,
North New Mexico Section, Albuquerque, N. M.

Fox, A. G., Microwave Propagation on Dielec-
tric Rods and in Ferromagnetic Media, I. R. E.-
A. I. E. E. High Frequency Measurement Confer-
ence, Washington, D. C., and Performance of Fer-
rites in the Microwave Range, I. R. E. Section,
New York, N. Y.

Galt, J. K., Domain Wall Motion in Ferrite
Single Crystals, I. B. M. Seminar, Poughkeepsie.

Geschwind, S., The Determination of Nuclear
Masses from Microwave Spectra, Physics Collo-
quium of New York University, New York, N. Y.

Goertz, Miss M., Action Pictures of Ferromag-
netic Domains, Society of Women Engineers-
American Association of University Women, New
York, N. Y.

Harvey, F. K., Focussing Sound with Micro-
Wave Lenses, A. S. M. E., Faculty Club, M. 1 T.,
Boston.

Hines, M. E., Latest Developments in Traveling
Wave Tubes, A. I. E. E. and I. R. E. Pittsburgh
Sections, Pittsburgh, Pa.

Karlin, J. E., The Construction of a Subjective
Scale of Weight, Psychology Seminar, Drew Uni-
versity, Madison, N. J.

Kircher, R. J., Transistor Circuit Network As-
pects, I. R. E. Princeton Section, Princeton, N. J.

Kock, W. E., Physics of Music and Hearing,
A. I. E. E. New York Section, New York, N. Y.,
and A. I. E. E. Philadelphia Section.

Lawson, C. C., and A. N. Gray (Western Elec-
tric Company ), Neoprene Jacketed Drop Wire,
Signal Corps Symposium, Asbury Park, N. J.

McKay, K. G., Experiments and Thoughts on
Secondary Electron Emission, University of To-
ronto, Toronto, Canada, and McGill University.

McMillan, B., The Modern Theory of Communi-
cation. Management Division, A. $. M. E., New
York, N. Y.; Society of Sigma Xi, New York Uni-
versity, New York, N. Y.; and Conference on Meth-
ods in Philosophy, New School for Social Study,
New York, N. Y. Information Theory, Institute of
Mathematical Statistics, Chicago, Il.

Odell, N. H., Physical Phenomena in Transistors,
Lehigh University, Bethlehem, Pa.

Olmstead, P. S., SQC in Engineering Research
and Development, A. A. A. S., St. Louis, Mo.

Read, R. K., Dislocation Theory of Grain Bound-
aries and Dislocation in Crystals, General Elec-
tric Company, Schenectady, N. Y., and Columbia
University, New York, N. Y.

Riesz, G. W., Stress Analysis, Society for Ex-
perimental Stress Analysis Meeting, New York.

Schelkunoff, S. A., Radiation Theory in Retro-
spect, Univ. of California, Berkeley, Calif.; Univ.
of California, Los Angeles, Calif.; Naval Ordnance
Test Station, Inyokun, Calif.; Naval Electronics
Laboratory, San Diego, Calif.; and U. S. Naval
Air Missile Test Center, Pt. Mugu, Calif.

Shewhart, W. A., Statistical Control in the Con-
servation and Utilization of Resources, Princeton
University, Princeton, N. J.

Shockley, W., Transistor Physics, Summit Asso-
ciation of Scientists, Summit, N. J.

Sittner, W. R., Transistors, University of Ken-
tucky and University of Louisville.

Struthers, J. D., Peacetime Applications of
Atomic Energy, Mens Club, Basking Ridge, N. J.

Teal, G. K., The Chemistry of Transistor Ma-
terials, Lafayette College, Easton, Pa.

Terry, M. E., Sensory Differences and Quality
Control, Princeton University, Princeton, N. J.,
and The Adaptation of the Rank Analysis to
Threshold Values, American Statistical Associa-
tion, Chicago, Ill.

Trenting, R. G., Some Examples of Funda-
mental Research in Communications Metallurgy,
Johns Hopkins University, Baltimore, Md.

Valdes, L. B., Transistors, A. I. E. E. and I. R. E.
Students Branches, City College of New York.

The Department of Defense has ap-
pointed a temporary committee to advise
the Secretary of Defense on certain aspects
of the problem of defense of the North
American continent against possible atomic
attack. Chairman of this temporary commit-
tee is M. J. Kelly. The other members
are Walker Cisler, President, Detroit Edi-
son Company; S. C. Hollister, Dean of Engi-
neering, Cornell University; F. L. Hovde,
President, Purdue University; C. C. Laurit-
sen, Professor of Physics, California Insti-
tute of Technology; Arthur E. Raymond,
Vice President, Douglas Aircraft Company:
H. S. Vance, Chairman of the Board, Stude-

M. J. Kelly, President of Bell Telephone Lab-
oratories, recently appointed Chairman of
Advisory Committee of the Department of De-
fense, is shown above (right) being congratu-
lated by Cleo F. Craig, President of the Ameri-
can Telephone and Telegraph Company, on
completion of thirty-five years service in the
Bell System,

baker Corporation, and R. E. Wilson, Chair-
man of the Board, Standard Oil Company
of Indiana.

The committee will be assisted in its
work by associates appointed from the De-
partment of Defense. The committee will
concern itself with over-all Department of
Defense policies, and programs aimed at

achieving a more effective condition of con-
tinental defense. Particularly, it will study
the possibilities of improved methods of
warning of hostile attacks, and the rela-
tion of such warning systems to other major
continental defense measures.

William Shockley received the first an-
nual Oliver E. Buckley Solid State Physics
Prize of the American Physical Society at
a banquet at Harvard University during
the January 22-24 meeting of the Society.
The award was made for Dr. Shockley’s
contributions to the physics of semi-con-
ductors.

Named for the former President of the
Laboratories, the prize of $1,000 is awarded
to a person adjudged to have made a most
important contribution to the advancement
of knowledge in solid state physics within
the five years immediately preceding the
award. The r recipient of the prize is chosen
by a committee appointed by the American
Physical Society.

During this past five years, Dr. Shockley
has made many contributions to solid state
physics including the theory predicting
junction transistors more than three years
before working units were announced pub-
licly. He is the author of Electrons and
Holes in Semiconductors, one of the re-
cent books in the Bell Laboratories Series.

A member of the National Academy of
Sciences, he is the holder of the I. R. E.’s
Morris Liebmann Memorial Prize, awarded
in 1951 in connection with his transistor
work. He is a Fellow of the American Physi-
cal Society, and a member of Tau Beta Pi
and Sigma Xi.

During 1952, A T & T reports, one new
telephone was added every four seconds
of each working day. Use of the telephone
continues to increase, and to meet public
demands and improve service still further,
all Bell System companies are keeping on
with heavy construction programs. In ac-
cordance with long range plans, new de-
vices and equipments are being put to work
in the over-all system, one objective of
which is to make it possible ultimately for
telephone users to dial their own long dis-
tance calls.

At the end of the year, there were about
39,350,000 Bell System telephones in serv-
ice, and people throughout the country
were using them at the rate of 149 million
conversations per day.

Eight out of ten Bell System telephones
are now dial operated, and four out of ten
long distance calls are being dialed by the
originating operator directly to the called
telephone.

New major long distance switching cen-
ters were placed in operation in Omaha,
Houston, and Cincinnati. There are now 18
of these centers which, interconnected with
other smaller systems, enable operators to
dial through to distant telephones in 1,625
cities and towns.

About 3,100 miles of coaxial cable and
radio relay routes were installed in 1952.
Altogetber, 16,300 route miles of these facil-
ities provide thousands of long distance
telephone circuits as well as 31,500 channel
miles for transmission of network and thea-
tre television programs over the nationwide
system. Coaxial cable and radio relay ex-
tensions brought 14 more cities into the
national television network.

New construction programs of the asso-
ciated companies required expenditures of

approximately one and a quarter billion
dollars. More than 1,900,000 telephones
were added, 2,000,000 miles of long dis-
tance circuits installed, and 850,000 re-
quests handled for changes in service — to a
line with fewer customers or to an indi-
vidual line. About one quarter million tele-
phones were added in rural areas, about
half of them on lines with more than four
parties, and progress continued in furnish-
ing the kind of service where it is only
necessary to lift the receiver to get the op-
erator or dial tone. At the year’s end, about
94 per cent of rural telephones were of this
type.

A new coaxial cable system, “L-3,” was
developed by the Laboratories. It will en-
able one pair of coaxial “pipes” to handle
simultaneously more than 1,800 telephone
conversations or 600 telephone conversa-
tions plus one television program in each
direction.

The transistor was given its initial trial
in the switching apparatus at Englewood.
Licenses to manufacture transistors under
Bell System patents were made available
to thirty-seven other companies by agree-
ment with Western Electric, whose own
output has been mostly for military uses.

Plans were completed for the mainte-
nance of essential telephone service in the
event of emergency. Aircraft warning sys-
tems were set up for civil defense and Air
Force filter centers. The Laboratories and
the Western Electric Company designed
and produced top secret electronic devices
as well as guided missiles, fire control
equipment for anti-aircraft) guns, radar,
atomic weapons, and a new field telephone
for the Signal Corps. Assistance was also
given the Signal Corps in the construction
of vital long distance communications link-
ing strategic areas in Alaska. More tele-
phone facilities were made available in
training camps and stations.

Bell System employees, including the
Laboratories and Western Electric, reached
nearly 700,000. A T & T share owners
passed 1,200,000, a gain of about 125,090
for the year.

H. S. Black joined Bell Telephone Laboratories
in 1921. In 1925 he was placed in charge of
groups developing repeaters, regulators, filters
and other circuits for carrier systems, and later
invented the stabilized feedback amplifier. He
also proposed the use of thermistors for the
regulation of telephone circuits. During World
War II he was concerned almost exclusively
with war developments. Since that time he
has been engaged largely in studies and de-
signs of radio pulse relay systems, and, more
recently, in transmission research,

H. S. Black, Transmission Research En-
gineer of Bell Telephone Laboratories, was
awarded the 1952 Research Corporation
Annual Award for Contribution to Science
at a dinner at the Waldorf-Astoria on Janu-
ary 23. This award was in recognition of
Mr. Black’s invention and development of
negative feedback systems and other con-
tributions to communications. Negative
feedback has come into general use not
only with carrier systems, but with radio
broadcasting, and other electronic and
communications fields.

In 1940, Mr. Black was honored by the
National Association of Manufacturers as
a Modern Pioneer and later was awarded
the John Price Wetherill Medal of the
Franklin Institute. He was also awarded a
Certificate of Appreciation by the War De-
partment in recognition of his development
work in connection with World War IL.
He is a Fellow of the A. I. E. E., also of the
I. R. E., and a member of Tau Beta Pi,
Sigma Xi, and of the American Association
for the Advancement of Science.

The plaque awarded to Mr. Black “for his in-
vention and development of the negative feed-
back system . . . and also to recognize a prolific
inventor whose achievements are attested by
many publications, patents, and contributions
in recent years to the development of ar
systems . . . Application of negative feed-
back has made possible the enormous ampli-
fications . . . upon which rest substantially the
structures of multiplex telephony, the servo-
mechanism art, the computing art, the entire
field of industrial control mechanisms . . .”

ration is made to scientists who have made
outstanding contributions to human know}l-
edge. It consists of a $2,500 honorarium, a
five-by-seven-inch bronze plaque, and a
citation. First given in 1925, it was granted
irregularly during the next decade, and in
1935 was established on an annual basis
contingent upon the availability of a suit-
able candidate.

Research Corporation is a non-profit
foundation which distributes its total net
income as grants in aid of research to col-
leges, universities, and scientific institu-
tions. It was established in 1912 by Dr.
Frederick Gardner Cottrell, scientist, teach-
er, and inventor, with the gift of his patent
rights in the field of electrical precipitation.
Its objectives are: (1) to receive and to
acquire inventions, and to render the same
more available and effective in the useful
arts; (2) to provide means for the advance-
ment of scientific investigation by contrib-
uting the net earnings of the corporation
to scientific and educational institutions,
and (3) to receive moneys and properties
and to apply them to the object specified.

The third meeting of the Deal-Holmdel
Colloquium for the season was held at
Holmdel, December 12. H. J. Williams
spoke on Ferromagnetic Domains. In his
talk, Mr. Williams showed slides of the do-
main patterns obtained in polycrystalline
perminvar, which studies had been made
in cooperation with Matilda Goertz. Some
of this work was published in the October,
1952, issue of the Recorp. Mr. Williams

also showed motion pictures of domain pat-
terns in silicon-iron crystals and discussed
the observation of domains in cobalt, work
which was done in cooperation with Mrs.
E. A. Wood and F. G. Foster.

Patents Issued to Members of Bell Telephone
Laboratories During November

Bardeen, J., and W. H. Brattain — Semiconductor
Amplifier and Electrode Structures Therefor —
2,617,865.

Clutts, C. E., G. A. Pullis, A. K. Schenck and
L. A. Weber — Alarm Signaling System — Re
23,571 (Reissue of Patent No. 2,583,088).

Cutler, C. C.—Frequency Changing Pulse Re-
peater Employing Phase Modulation — 2,619,543.

Etheridge, H. A., Jr. — Automatic Measurement
of Transmission Characteristics — 2,617,855.

Pierce, J. R. — Communication System Employing
Pulse Code Modulation — Re 23,579 (Reissue of
Patent No. 2,538,266).

Spencer, H. H., see B. H. Hamilton,
Stone, J. R.-- Regulating Apparatus — 2,619,630.
Tinus, W. C.— Object Location System — 2,617,094.

Vroom, E. — Selective Signaling System — 2,619,528.
Weber, L. A., see C. E. Clutts.
Wooldridge, O. E., see R. H. Griest.

For years the telephone you know and use has
done its job well—and still does. But as America
grows, more people are settling in suburban
areas. Telephone lines must be longer; more
voice energy is needed to span the extra miles.

The new telephone shows once again how Bell
Telephone Laboratories keeps making telephony
better while the cost stays low.

Improving telephone service for America provides careers
for creative men in scientific and technical fields.

New “S500” telephone. it has already been
introduced on a limited scale and will be put
in use as opportunity permits, in places where
it can serve best. Note new dial and 25 per
cent lighter handset.

Transmitter is much more powerful, due
largely to increased sound pressure at the
diaphragm and more efficient use of the
carbon granules that turn sound waves into
electrical impulses.

produces times as much acoustic energy
for the same input power. It transmits more
of the high fcequencies.

Improved dial mechanism can send pulses
over greater distances to operate switches in
dial exchange.

Built-in varistors equalize current, so voices
don’t get too loud close to telephone exchange.

Despite increased sensitivity of receiver,
“clicks” are subdued by copper oxide varistor

Bell Laboratories Record  1953-02: Vol 31 Iss 2