WHEN CHANGES ARE MADE IN THIS DRAWING
ONLY THOSE SHEETS AFFECTED WILL BE
REISSUED.

THIS SHEET INDEX WILL BE REISSUED ANC
BROUGHT UP 10 DATE EACH TIME ANT SHEET
OF THE DRAWING IS REISSUED. OR A NEW
SHEET IS ADDED.

THE ISSUE NUMBER ASSIGNED TO A CHANGED
OR NEW SHEET WILL BE THE SAME ISSUE
NUMBER AS THAT OF THE FIRST SHEET.

5. THE LAST ISSUE NUMBER Of THE FIRS' SHEET
INOEX IS RECOGNIZED AS THE LATEST ISSUE
NUMBER OF THE DRAWING AS A WHOLE.

RESISTANCE VALUES ARE IN OHMS
CAPACITANCE VALUES ARE IN MICROFARADS
VALUES PRECEDED BY THE SYMBOL *(PLUS)
OR -(MINUS) ARE IN VOLTS

NOT FOR USE OR DISCLOSURE OUTSIDE THE BELL
SYSTEM EXCEPT UNDER WRITTEN AGREEMENT.

THE READ CIRCUIT CAN OPERATE IN EITHER OF TWO MODES,
NORMAL DATA TRANSFER OR MAINTENANCE DATA TRANSFER. IN
THE NORMAL MODE DATA IS TRANSFERRED FROM THE CARTRIDGE
TAPE TRANSPORT (CTT). IN THE MAINTENANCE MODE, THE REV
ANO WRITE CIRCUITS CAN BE EXERCISED WITHOUT OPERATING
THE CTT. DATA WILL ENTER DIRECTLY FROM THE OUTPUT OF
THE WRITE CIRCUIT LOCATED ON JK18 (SEE FIG. 1). THE
DATA AND ITS ASSOCIATED CLOCK ENTERS THE READ CIRCUIT
THROUGH THE DATA SELECTOR ANO THE CLOCK SELECTOR
CIRCUITS, RESPECTIVELY. THE DATA CLOCKING CONTROL
CIRCUIT WHICH RECEIVES CLOCK PULSES FROM BOTH THE CLOCK
SELECTOR CIRCUIT AND A FREE RUNNING CLOCK (OPERATING AT
THE NORMAL DATA FREQUENCY) HAS TWO BASIC CLOCK OUTPUTS.
THE OUTPUT LABELED SHIFT PULSES BEGINS CLOCKING THE 24-
BIT DATA REGISTER ANO THE DATA FRAME CIRCUITRY (THE DATA
FRAME CIRCUITRY INCLUDES LOGIC FOR STRIPPING THE PRE-
AMBLE AND POSTAHBLE) AS DATA INITIALLY ENTERS THE READ
CIRCUIT. AS THE PREAMBLE (FIFTEEN ZEROS FOLLOWED BY A
SINGLE ONE) IS SHIFTED THROUGH THE 24-BIT REGISTER, THE
OUTPUT OF THE DATA FRAME CIRCUIT INHIBITS CLOCK PULSES
TO EOTH THE C?C CHECK CIRCUIT AND THE BUFFER CIRCUITS
(THE BUFFERS ARE CLOCKED BY THE LEAD LABELED CLOCK OUT).
BY MONITORING THE OUTPUT OF THE 24-BIT REGISTER, THE
DATA FRAME CIklUIT DETECTS THE FIRST ONE (LAST BIT OF
THE PREAMBLE) AND THEN ENABLES THE CRC CHECK CIRCUIT
AND THE CLOCK OUT LEAD. THIS ALLOWS THE FOLLOWING DATA
TO BE CLOCKED INTO THE CTC CHECK CIRCUIT AND TO THE
BUFFER CIRCUITS. THIS IN EFFECT, STR I PS THE PREAMBLE
FROM THE DATA BY SIMPLY IGNORING IT AS IT FALLS OUT THE
END OF THE 24-B'T REGISTER.

AS IN A NORMAL READ OPERATION. WHEN THE DATA FRAME
COUNTER REACHES A COUNT OF 16, ALL OPERATIONS WILL
BE TERMINATED, LEAVING THE BUF FILL LEAD ENABLED.

THE READ DATA CLOCK LEAD (RDCLKO) WHICH COMES FROM THE
CTT. FEEDS THE 1>is HONOPULSER RDCLK1. THIS MONOPULSER
PROVIDES A DELAY T. ENSUR r THAT THE DATA LEAD (RDDATO)
FROM THE CTT IS STABLE BEFORE CLOCKING INFORMATION INTO
THE OVERROW REGISTER 0FLREG. THE ZERO OUTPUT OF RDCLK1
SERVES AS A TEST POINT WHICH IS BROUGHT OUT TO A CONNEC-
TOR TERMINAL. THE ONE OUTPUT OF RXLK1 FEEDS THE NAND
GATE TSTO WHICH IS ENABLED BY BOTH MAINTO ANO ENRD1.
MAINTO IS AN OUTPUT OF THF MAINTENANCE RIP-ROP ON JK16.
IT IS AT A HIGH LEVEL WHEN T HE CTTC IS NOT IN A MAIN-
TENANCE MOOE. ENRD1 IS AN OUTPUT OF THE READ RIP-ROP
ON JK16. IT IS AT A HIGH-LEVEL WHENEVER THE CTTC IS
HANDLING DATA (REAO, WRITE AND CRC SHIFT OPERATIONS).
TSTO FEEDS RDST1 WolCH CLOCKS THE DATA THROUGH THE THREE
8-BIT REGISTERS SSRREG, PSTREG1A, ANO PSTREG1B. THE
DATA !S FED INTO BRREG BY RDATA1 WHICH PASSES DATA FROM
EITHER THE CTT OR FROM THE WRITE CIRCUIT (JK18) DEPEND-
ING UPON THE ENABLING OF EITHER TDATAO OR HOATAO BY MAINTO OR
MAINT1, RESPECTIVELY. HAINT1 IS THE SECOND OUTPUT OF THE
MAINTENANCE FLIP-FLOP ON JK16.

IN THE MAINTENANCE MCOE THE READ AND WRITE CIRCUITS CAN
BE EXERCISED WITHOUT OPERATING THE CTT. MAINTO WILL BE
AT A LOW LEVEL AND HAINT1 WILL BE AT A HIGH LEVEL. THIS
ENABLES A DATA PATH FROM WDATA1 AND A CLOCK PATH FROM
WB11 THROUGH MSTO. THIS STATE DISABLES THE OATA AND
CLOCK PATHS FRC? THE CTT. WDATA1 ANO W011 ARE DATA AND
ASSOCIATED CLOCK LEADS FROM THE OUTPUT OF THE WRITE
CIRCUIT.

INPUT DATA WHETHER CLOCKED FROM THE WRITE CIRCUIT OR FROM
THE CTT IS CLOCKED THROUGH THE THREE REGISTERS BRREG,
PSTREG1A, AND PSTREG1B. THESE ARE 41T 8-BIT -1HIFT
REGISTERS WHIG" MAKE UP A 24-BIT SERIAL SHIFT REGISTER.
THE OUTHJT OF THIS REGISTER RDDATAB IS ANDeo WITH ROST1
BY DAFRENO. DAFRENO WILL PROVIDE A TOGGLE PULSE WHICH
CLEARS DAFR ON THE FIRST REAO-CLOCK PULSE /'FTER RDDATAB
GOFS TO THE ONE STATE. THE FIRST WORD OF A DATA 8; OCK
IS THE PREAMBLE (15 "ZEROS" FOLLOWE3 BY A SINGLE "ONE").
THEREFORE, THE CLEARING OF DAFR IMPLIES THAT THE FIRST DATA
BIT FOLLOWING THE PREAMBLE IS AT THE OUTPUT OF THE 24-BiT
REGISTER. WHEN THE CTTC IS IN THE MAINTENANCE MODE,
THE FIRST WORD FROM THE WRITE CIRCUIT IS ALSO THE PRE-
AMBLE. ALL DATA-CLOCK PULSES WHICH FEED EITHER THE
CRC CIRCUIT OR THE BUFFER CIRCUITS WJST PROPAGATE
THROUGH THE NAND GATE, RDSTG. RDSTO HAD BEEN INHIBIT-
ED BY THE SET STATE ON DAFR UNTIL AFTER THE LAST BIT OF
THE PREAMBLE. SliiCE NO CLOCK PULSES ARE PERMITTED
THROUGH RDSTO, UNTIL AFTER THE PREAMBLE HAS BEEN SHIFTED
FROM THE 24-SIT REGISTER, THE PREAMBLE IS STRIPPED FROM
THF DATA STREAM. THE CLEARED STATE OF DAFR ENABLES
R^STO. THE OUTPUT OF RDSTO PROVIDES DATA CLOCK PULSES
TO THE 16-STATE WORD FRAMING COUNTER f WFRCT), THE READ
SHIFT PULSE MONOPULSER (RSTPUL), THE CLOCK INPUTS TO THE
CRC REGISTER, AND SHCRC1.

IN THE NORMAL DATA TRANSMISSION MODE, DATA WHICH APPEARS
AT THE Q8 OUTPUT OF PSTREG1B PROPAGATES THROUGH RDDATO,
TD0UTO, AND DflUTI TO THE D CELL OF CRCRGA. IT IS LOADED
ONTO THIS RIP-ROP BY SHCRCO. THE OUTPUT OF THIS CELL
(RDBUT1) IS THE DATA OUTPUT SIGNAL FROM THE CTTC'S RE/1
CIRCUITRY. SHCRCO ALSO CLOCKS THE Q8 OUTPUT OF PSTRE-IB
THROUGH THE CRC ERROR DETECTION CIRCUIT.

AS DATA IS BEING SHIFTED THROUGH THE CRC CIRCUITS AND THE
OUTPUT RIP-ROP, RDSTO IS ALSO PROVIDING CLOCK PULSES
TO THE 1iis MONOPULSER, RSTPUL AND THE 16-STATE WORD FRAME
COUNTER, WFRCT. THE OUTPUT OF RSTPUL (RSP1) SERVES AS
THE REAO-OATA CLOCK TO THE BUFFER CIRCUIT. DATA IS CLOCKED
INTO THE BUFFERS ON THE TRAILING EDGE OF RSP1 . THIS ALLOWS
DATA FROM PSTREG1B TO BE SETTLED IN THE D CELL OF CRCRGi
BEFORE THE BUFFER IS CLOCKED.

WHEN THE READ CIRCUIT IS IN THE IDLE STATE (NO DATA IS
SEING TRANSFERRED THROUGH IT), D«D1 THE ONE OUTPUT
OF THE REAL FLIP-ROP ON JK16 IS AT A LOW LEVEL. THIS LOW
LEVEL MAINTAINS A SET STATE ON THE D-TYPE RIP-FLOP
RADJEN AND BY DRIVING THE OUTPUT OF RDCL1 HIGH, IT MAIN-
TAINS A LOW LEVEL AT THE OUTPUT OF RCLKO. THE LOW LEVEL
AT THE OUTPUT OF RCLKO RETAINS A CLEARED STATE ON THE
OUTPUT OF THE D-TYPE RIP-ROP ADJSYN AND A SET STATE
AT THE OUTPUT OF DAFR. THE LOW LEVEL AT THE ZERO
OUTPUT OF DAFR HOLDS WFRCT IN ITS CLEARED OR INITIAL
STATE. THIS ENSURES THAT THE COUNTER WILL BEGIN COUNTING
AT THE ZERO STATE ON THE FIRST CLOCK PULSE AFTER THE
PREAMBLE HAS FALLEN FROM PSTREG1B. AS A READ OPERATION
BEGINS THE CLEAREO STATE OF ADJSYN ENABLES CLKINH AND
DISABLES ENCLKO. THE ENABLED CLKINH ALLOWS READ-CLOCK
PULSES FROM RDST1 TO PROPAGATE THROUGH ADJCLK1 TO THE
INPUT OF ENCLKO WHICH IS DISABLED, AND TO ADJCLKD. THE

IN THE MAINTENANCE STATE THE READ CIRCUIT OPERATES IN A
VERY SIMILAR MANNER. MAINTO WILL BE LOW AND MAINT1 WILL
BE HIGH. DATA THAT COMES DIRECTLY FROM THE WRITE CIRCUIT
(JK18) WILL APPEAR ON WDATA1. THE CLOCK WILL APPFfR ON
U011 (ALSO FROM JK18). AT THE END OF THE INPUT DATA
RDADJ1 WILL BE DRIVEN HIGH BY THE WRITE CIRCUIT. THIS
ALLOWS THE REAO ADJUST CLOCK CLK011 TO PROPAGATE THROUGH
RAWAOJO.

THE CRC CIRCUIT MONITORS ALL DATA READ INTO THE READ CIR-
CUIT WHEN THE CTTC IS IN THE NORMAL OPERATING MODE, THE
CRC REGISTER IS CLEARED BY A PULSE ON THE RDCLO (OUTPUT

TRANSFER OPERATION. WHEN THE CTTC IS IN THE MAINTENANCE
MODE THE CRC REGISTER IS CLEARED BY ISSUING A CLEAR CRC
ORDER WHICH APPEARS AS A PULSE ON THE CLRCRCCO INPUT
LEAD. CLRCRCOO IS AN OUTPUT FROH THE CTTCs COMMAND DE-
CODER LOCATED ON JK16. THE CRC REGISTER IS HADE UP OF:
CELLS A.B.AND C OF CRCRGA, ALL OF CRCRGB.AND LRLt 1,2,5,
4 ANO 5 OF CRCRGC. CRCRGA IS OPERATED IN A PARALLEL HOOE
WHERE THE OTHER TWO REGISTERS ARE OPERATED IN THE SERIAL
MODE. THE 16 BITS OF THE CRC REGISTER ARE ORGANIZED IN
FOLLOWING MANNER; BITS 0,1, AND 15 ARE CRLS A,B , AND
C OF CRCRGA, RESPECTIVELY. BITS 2,5, 4,5,6,7,8, MO 9
ARE CELLS 1,2,5,4,5,6,7, AND 8 OF CRCRGB, RESPECTIVELY.

BITS 10,11,12,15, AND 14 ARE CRLS 1,2,5,4, AND 5 OF CRCRGC,
RESPECTIVELY. CRC1D1 PERFORMS AN EXCLUSIVE 0R FUNCTION ON'
RDDATAB (INPUT DATA TO THE CRC CIRCUIT) AND BIT 15 OF THE
CHECK REGISTER. THE OUTPUT OF CRC1D1 IS ENABLED THROUGH
GATES CRCDENO AND CRCD1 BY SHEN. THE OUTPUT OF CRCD1
FEEDS BIT OF THE CHECK REGISTER, ANO IS EXCLUSIVELY 0Red
WITH BIT 1 BY CRC501 TO FEED BIT i, AND BIT 14 BY CR15D1
WHICH FEEDS BIT 15 OF (HE CHECK REGISTER. THIS CIRCUIT
IS A CYCLIC-REDUNDANCY CHECKER FOR THE GENERATOR POLYNGMINAL
, + x 2 + x 15 ♦ X 14 . ER1A0, ER1B0, ER1C0, ER1D0, ER1E0,
ER1F0, ER1G0, ER1H0, AND ESDET1"0R"THE 16-OUTPUT BITS OF
THE REGISTER TOGETHER AND INDICATE IF ANY OF THE 16 CELLS
CONTAIN A "ONE." (THiS INDICATES AN ERROS CONDITION
AFTER AN ENTIRE BLOCK OF OATA HAS PASSED THROUGH THE
CIRCUIT.) THE OUTPUT OF ER0ET1 IS ENABLED THROUGH
CRCERO BY EREKIN1. ERENIN1 IS HIGH WHENEVER THE CTTC IS
NOT IN A READ OR REAO-AFTER-WRITE MOOE (THE READ CIRCUIT
IS NOT TRANSFERRING DATA).

JK17 Circuit Pack, cartridge tape transport, board B controller circuit


UNLESS OTHERWISE SPECIFIED:
RESISTANCE VALUES ARE IN OHMS
CAPACITANCE VALUES ARE IN MICKOFARADS
VALUES PRECEDED BY THE SYMBOL ♦ (PLUS)
OR - (MINUS) ARE IN VOLTS.

2. FOR REISSUES, A CHANGED
OR NEW SHEET IS ASSIGNED
THE SAME ISSUE NUMBER AS
SHEET 1.

. . THE ISSUE NUMBER OF
SHEET 1 IF RECOGNIZED AS
THE ISSUE NUMBER OF THE
WHOLE DRAWING.

CIRCUIT DESCRIPTION/TIMING
JL16 WRITE TiHING EXAMPLE
ADDRESS (CEA0I1 THROUGH CEA2I1)

THE JL16 MEMORY PLANE CONTAINS RANDOM-ACCESS STORAGE ELEMENTS
MADE UP OF 16K BY 1 BIT (K ■ 1024) INSULATED GATE FIELD
EFFECT TRANSISTOR (IGFET) fAJAL IN-LINE PACKAGES (OIPS)
ARRANGEO IN A 12BK BY 2-BI f ARRAY. THE MEMORY IS VOLATILE,
IN THAT THE STORED INFORMATION WILL BE LOST IF POWER IS
INTERRUPTED. AND DYNAMIC, IN THAT THE S T ,rfED INFORMATION
MUST BE REGENERATED (REF«SHEO) AT SPECIFIED INTERVALS. IN
ADDITION TO STORACE ELEMENTS, THE MEMORY PLANE CONTAINS
ADDRESS AND DATA BUFFERS, CONTROL LOGIC, DEVICE SELECT
DECODERS. ALL INPUTS AND OUTPUTS ARE +5 V TTL COMPATIBLE.

ADORESS BITS CEA0I1 THROUGH CEA2I1 ARE GATED BY ONE OF THE
TIMING SIGNALS RASIO AND ARE USED TO SELECT 2-0F-16 MEMORY
DIPS. THE 16K RAM REQUIRES 14 ADDRESS BITS WHICH ARE
MULTIPLEXED TO THE MEMORY PLANE ON INPUTS GRCAOO THROUGH
GRCA60. THESE SIGNALS ARE BUFFERED AND CONNECTED TO ALL
MEMORY D*PS. A SECOND TIMIN3 SIGNAL, CASIO, IS NECESSARY TO
ACHIEVE PROPER OPERATION. THIS SIGNAL IS BUFFERED INTO TWO
BRANCHES WHICH EACH DRIVE EIGHT DEVICES IN THE MEMORY ARRAY.

THE MEMORY PLANE IS PUT INTO THE "WRITE MODE" BY FORCING A
LOW LEVEL ON RWIO. DATA IS WRITTEN FROM INPUTS WRTDOIO AND
WRT01I0 DURING THE TIME WHEN BOTH RASIO AND CASIO ARE LOW.

DATA IS READ FROM THE MEMORY DEVICES WHEN RWIO IS HIGH AND
BOTH RASIO AND CASIO ARE LOW. DATA IS THEN GATED TO OUTPUTS
PTWV1 AND RD010. THE DATA OUT TRANSITIONS ARE SHOWN IN THE
READ TIMING EXAMPLE, CASIO STAYS HIGH DURING REFRESH CYCLES.

EACH STORAGE CEIL ON THE MEMORY RANE MUST BE REFRESHED AT
LEAST ONCE EVERY 4.4 ins, OR ELSE THE STORED CHARGE WILL LEAK
OFF CAUSING THE DATA TO BE LOST. THIS REFRESH OPERATION CAN
BE ACCOMPLISHED BY ENABLING THE RASIO INPUT IN THE SAME
MANNER THAT IT IS PERFORMED DURING A READ CYCLE WHILE THE
CASIO INPUT IS INHIBITED. THIS MUST BE PERFORMED FOR EACH
OF THE 128 ROWS OF EACH OF THE MEMORY DIPS AT LEAST ONCE
EVERY 4.4 ■». THE REFRESH OPERATION FOR THIS MEMORY PLANE
CAN BE PERFORMED IN 128 CYCLES BY FORCING REFIO TO THE LOW
STATE AND EXECUTING A CYCLE THAT ENABLES RASIO BUT INHIBITS
CASIO AT EACH OF THE 128 STATES OF ADDREFS INPUTS RCAOIO
THROUGH RCA6I0 AT LEAST ONCE EVERY 4.4 at.

JL16 Circuit Pack, 128K x 2 bit memory plane circuit


These drills are thoroughly reliable, strongly built, light in weight and convenient in shape. They
operate on either alternating or direct current and are reversible. Attachment is made to the ordinary
drop cord or incandescent lamp socket.

Model Bs Has the breakover feature for changing drills or taps instantly by hand without the use of
chuck wrench or key.

Model C: Has two speeds, the gears running in grease. It has the offset spindle, allowing close quarter

This tool is not only adapted for grinding centers on lathes, but also for grinding dies, reamers and
cutters and for universal grinding as well.

Tk*® t°°l very useful for buffing and polishing brass, steel and other metals hnd when equipped with
thcsmall emery wheel is w$ll adapted for light grinding also.

♦Delivery F. O. B. Factory, Leipsic, O. For warehouse deliveries write nearest house.

Model A Drill. This tool was designed for drilling in either metal or wood. It will run on either
alternating or direct current. The offset spindle allows drilling in close corners. The main driving
spindle is run in a tobin bronze bushing, two inches in length. The lower handle can be readily removed
when necessary.

The body is made of aluminum thoroughly strengthened and supported where the strain is most severe.
^ gements are made for positive and effective oiling for the motor shafts, driving spindle and all parts
are subjected to wear. The gears are accurately machined and run in grease. This drill is very light
W C ° nVen ^ en ^ handle. It is especially useful for drilling in sheet metal of all kinds. Also for drilling
g plate and oiler holes and for light drilling in wood.

. 0 Drill. Specially designed for drilling in cast iron, brass and other soft metals. Also for light

cente ^ ^ enera ^ construction is similar to Model A drill except in Model 0 drill the chuck spindle is in the
spindle ^ e mo ^° r body and is directly connected to the motor shaft without gear reduction. The chuck
currp rUDS m bronze bushing of ample bearing surface; will operate on either alternating or direct

These hammers will do the work of pneumatic tools of like capacity at about 15% of the power cost and
without the expense and inconvenience of compressor, air piping nose, etc. Over hand work, the economy
is from 80% to 90%, and it is by no means uncommon for a tool to save its cost in a week. Every tool is
controlled by a switch mounted in the handle and equipped with flexible cord and plug. They may be
attached to any lamp socket.

These hammers are built in two types: For direct current and for universal service. The Universal
tools operate on either direct current or alternating current of any commercial frequency. These tools are
particularly adapted for putting up fixtures on a concrete ceiling, dressing Frencn burr stones in a paint
mill, cleaning scale off of condenser tube, for channeling plaster in an office building, for bush hammering
a concrete wall, for drilling solid concrete, drilling for pipe racks in a brick wall, chipping gray iron castings,
cutting openings for I beams, etc.

Supporting stands are strongly recommended for all overhead work. The use of these stands takes the
jar and strain off the operator and keeps the tool pressed tight against the work.

The proper selection of steels to be used in different kinds of material is extremely important.

For stand to be used with the above electric hammer, literature and prices fur nish ed on application.

Note: The capacities given are conservative and approximate. The tools cannot be forced, the
strength of the blow is constant and the capacity depends upon economical drilling speeds only. There is
no danger of burning out the machines.

Each tool is complete with 10 feet of cord and plug and runs from a lighting socket.
Delivery F. O. B., Chicago, Ill. For warehouse deliveries write nearest house.

are “synchronous’* for alternating current motors and “full load" for direct current

rl_Jf 0t0r8 hsted above are the so-called domestic buffing and grinding outfits and consist of totally en-
c «tor mounted on a high base and furnished with separable straight shaft extension attachments
together with a 3 l A inch rag buffing wheel and a 3 inch emery grinding wheel, which are
meiudea at prices indicated; and may be used as separate sale prices as well as allowances.

ice angle phase motors are provided with solid armatures, i.e., without clutches. The above motors
^ not furnished for two or three-phase circuits.

p_jTjmnr j. ra ? buffing wheel, B—3 inch emery grinding wheel, C—Straight spindle shaft attachment,

eluded at in ftnrr«F\ 1 ,' 8 nna inch shafts are furnished complete with 6y% men rag oumnj,

Not*; tu. ttachnient may be used for light drilling purposes, drills not furnished.
ttDeliverv F n o ^ or % H inch shafts are not applicable to oil ring bearing rnoto
j' • o, o. Factory, Lynn, Mass. For warehouse deliveries write nearest house.

Western Electric : Electric Drills : Electric Hammers : Buffing and Grinding Outfits : 1916


ORIGINALLY, the ceramic parts used in the telephone and
associated equipment were not manufactured by the Western
Electric Company because the technical requirements and volume of
consumption of such parts did not warrant the development or estab-
lishment of processes or the facilities for manufacture. The later
development of such manufacturing processes for some of the ceramic
parts has been necessitated largely by inability to secure an adequate
supply of parts meeting the close limits required for satisfactory
functioning of the apparatus, although there have usually been other
influencing factors. Such developments have, in most instances,
been advantageous from an economic standpoint. The experimental
work has been confined to that required fdi*' the above ends and
only a very limited amount of research work has been done. Some
of the major projects for which it was necessary to develop new methods
of processing to obtain the desired quality at a satisfactory cost are
outlined.

Switchboard Lamp Cap Lenses
The first major project undertaken was the development for manu-
facture of switchboard lamp cap lenses of the types shown in Fig. 1.
One factor necessitating this undertaking was the difficulty experienced

tional compositions were then made of talc and clay with and without
sodium silicate and feldspar. It was found that most satisfactory
results were obtained with a ball clay, kaolin, and talc body in the
proportions of forty per cent, ten per cent and fifty per cent, and this
body was therefore adopted.

Originally, attempts were made to cut the groove in the fired core
with a diamond tool but this resulted in excessive chipping of the

groove. A chaser with alternate teeth was then tried out, with the
thought that the gradual cutting action would prevent chipping.
This also proved unsuccessful. The use of a circular saw, emery
wheel, and a phosphor bronze disc charged with diamond dust were
also considered. These methods were not completely satisfactory
although better results were obtained. Rolling the thread in the core
while in the leather hard state after extrusion was then tried with
good results and a suitable machine was developed for performing
this operation.-

With this machine, an extruded blank of slightly oversize diameter
was placed on a revolving mandrel. An arm was provided to hold a
shaving tool ahead of a disc which formed the thread. This arm was
attached to a segment of a nut and the movement of the arm when
the nut segment was engaged with a thread integral with the mandrel,
shaved the core to exact diameter and carried the disc longitudinally
across the core forming the spiral groove. An auxiliary arm carrying
two knives was then engaged which cut the core to exact length and

factory^ results could be obtained with 10-24-mesh material and a
12.75 per cent ± .75 per cent moisture content. This moisture content
was sufficient to give a compact part and body mix still could be fed
satisfactorily to the dies. Methods of^processing the body mix were
then worked out to hold it within these limits.

The use of material within these close size limitations involved
considerable effort to establish economical methods of production.
Common practice consisted of slaking the clay in water, adding the
other body ingredients, mixing thoroughly with water, filter pressing,
complete drying, addition of water to obtain the desired moisture
content, aging and screening. The effect of aging was investigated
and found negligible with the moisture content to be used and it was
therefore decided to dry the material after filter pressing to the
required approximate twelve per cent moisture content before the
disintegrating and sizing operations. Methods of handling were
evolved to obtain a maximum percentage of material between 10 and
24-mesh and to regranulate the fines without again mixing them with
excess water.

Various methods of economically removing fins after forming were
investigated and initially the fired parts were tumbled with small
porcelain balls. This method removed fins and produced smooth
surfaces. Another advantage of the method was the automatic
elimination of any weak or flawed parts by breakage during the
tumbling. Later, further developments in methods of firing described
hereafter made it more economical to remove the fins in the raw state
by vacuum brushing the parts in multiple after they were arranged on
trays at the pressing machines.

Initially the parts were fired using the practice then commonly
followed in the industry. With this method, the parts were placed
in saggers and fired in an intermittent kiln. This method involved
costly handling, heat losses due to heating and cooling the furnace at
each firing, and considerable expense from sagger replacements. A
small continuous kiln was therefore installed in which the parts were
carried in layers on top of cars through successive preheating, firing,
and cooling zones which were continuously maintained at definite
temperatures, the heat from the cooling fired ware being used to heat
the incoming ware.

Summarizing, the method of manufacture finally developed for
porcelain blocks consisted in mixing feldspar, clay and flint with water
to get an intimate mixture, filter pressing, drying to proper moisture
content, sizing, automatically molding the parts, removing fins in
multiple, and firing in a continuous kiln. This method resulted in a

possess these properties and excellent results were obtained from their
use. 3 These substances were made from kelp. Their most interesting
property as a suspending medium was the ability of the alginates when
added to water even in small percentages to make solutions of high
viscosity. For example, water solutions of ten per cent ammonium
alginate would stand stiff. Some of the advantages in our use of
alginates for suspending number plate enamel were: (1) uniformity of
composition resulting from the alginates being a manufactured product
rather than a natural mineral ; (2) the fact that dried sprayed coats of
alginate suspended enamel were less subject to damage from handling;
(3) a low decomposition temperature which resulted in the material
being driven off before fusion of enamel, thus avoiding bubbles in the
enamel ; and (4) increased resistance of the finished enamel surfaces to
chemical attack and their ability to withstand greater mechanical shock
and distortion without damage, since any refractory materials present
when the enamel was fired would not be completely fused or incor-
porated into the glass, leaving points more readily attacked chemically
as well as lines of mechanical weakness.

Using alginate suspended enamels, suitable manufacturing processes
were developed for the application and firing of enamel and the appli-
cation of characters to the fired plates. A machine was devised for
the application of the sifted coating, and rotary continuous furnaces
were installed for the firing operations.

Originally the decalcomania method was used for character applica-
tion. In this process, the enameled parts were first coated with a thin
coat of sizing and, after partial drying, they were placed in a locating
fixture mounted on a small arbor press and pressure was applied to a
properly located transfer by means of a soft rubber pad. The paper
backing of the transfer was then removed by soaking in water and, to
insure contact, the characters were repressed with a silk covered pad.
The sizing was then baked off before firing to remove organic materials
and eliminate shadows around the characters. This method was
costly and even well trained, careful operators did not produce satis-
factory plates.

To eliminate these defects, an offset printing and dusting method
was developed in which an electrotype printing plate was covered with
printer's ink and an impression was transferred to the number plate
by means of a rubber transfer pad. Powdered vitrifiable colors were
then dusted over the entire surface of the plate and the unprinted
areas of the part brushed clean with a camel's hair brush. In printing
two color plates, the black letters were printed and dusted first, after

ceramic printing ink covered tests on various printing vehicles to deter-
mine what vehicle or mixture of vehicles would be most suitable.
Difficulty was encountered in incorporating a sufficient amount of
inert, finely pulverized, intensely colored glasses into a vehicle and
still retaining the properties essential for offset printing by transferring
an impression from an electrotype plate to a vitreous enamel. This
problem was finally solved by the use of a relatively large percentage
of uncalcined ceramic material in combination with light and heavy

ink varnishes. 4 Motor driven presses using this ink were also devel-
oped to facilitate the printing operations. 5

The manufacture of these parts was undertaken primarily to
eliminate an undesirable supply situation but Western Electric manu-
facture resulted in improvements in quality of enameling, quality of
printing, and in mechanical strength. This latter characteristic was
important since it reduced assembly losses from cracked plates.

While vitreous enameled copper base number plates have been
replaced by other types, the developments outlined were the basis of
subsequent enameling developments.

Vitreous Enameled Iron Base Number Plates
The low level of illumination at some pay stations led to the design
by the Bell Telephone Laboratories of a large iron base number plate,
shown in Fig. 6, to be mounted flush with the finger wheel of the dial.
Since the demand for these plates was relatively small, they were
originally made by the usual process followed in the industry in enamel-
ing similar articles. This process consisted of applying and firing one
ground coat for adherence and then applying and firing two sprayed
cover coats to obtain the whiteness and opacity desired; all being
felspar enamels. The whiteness was not as good as that obtained on
the copper base plates with lead enamels and in addition considerable
difficulty was experienced in the field due to the fading of the characters
as a result of chemical action on plates exposed to corrosive gases such
as sulphurous fumes in certain locations. The process was also costly.
Since maximum whiteness and opacity was obtainable in the lead-
arsenic type of enamels previously described when applied by dusting
on dry, it was desirable that the coating be applied in this manner.
In order to avoid several enamel applications and firings, it was also
desirable that other portions of the plate be protected by some corrosion
resistant coating other than vitreous enamel which would necessarily
have to retain such corrosion resisting properties after exposure to a
temperature of 1500° F. for six minutes and also be capable of being
enameled with satisfactory results. Numerous coatings were tried and
it was found that a Western Electric black oxide finish on iron would
satisfactorily meet all requirements. 6 Using this finish, it was possible
to fuse the enamel directly on the upper surface of plates, to retain
corrosion resistant qualities on all other exposed surfaces, and to reduce
the number of process operations. A number plate of greatly improved
appearance and durability also resulted. In addition, the curved

fired parts to the desired thickness of 0.030 inch. This operation was
costly and losses from breakage were high. The narrow dimensional
limits of ±.002 inch on thickness were also hard to maintain because
of the difficulty of keeping the lapping surfaces parallel. In view of
this, it was decided to machine the parts from natural talc rod or lava.

The mineral talc or lava, being soft, was easy to machine and the
firing shrinkage was only one per cent as compared to about ten per
cent with dry pressed porcelain. While less difficulty with warpage
and dimensional variations was experienced, the machined surfaces,
while reasonably smooth and accurate, were not equal in quality to
surfaces obtainable with molded parts. The chief difficulty with the
process was in obtaining a satisfactory raw material free from flaws
and fissures. The first work was done with domestic lava which was
somewhat granular in structure but large rejections resulted from pitted
surfaces and chipped edges. A survey of domestic lavas showed that
only a small percentage was sufficiently dense. Chinese white lava
was found to be homogeneous and fine grained but of uneven shrinkage.
Best results were obtained with Italian green lava and this material
was used in commercial production. Due to breakage because of
fissures, the number of good insulators per foot of rod was very low and
the manufacturing cost was therefore excessive.

In view of this, various domestic manufacturers of glass, porcelain,
lava and other types of ceramic parts were canvassed but no source
of supply that could meet the required quality limits could be located.
It was therefore decided to make a thorough investigation of new
molding compositions for the job. As a first step in this study, it
was necessary to do away with drying shrinkage which required
a binder which would give sufficient strength in the raw state to
withstand the various finning and handling operations prior to firing.
It was also desirable that such a binder should not affect the fired
structure of the parts. Various organic substances such as pitches,
phenolic resins, asphalts, paraffins, and waxes were tried in both
hot and cold molded bodies. It was found that a large percentage
of these binders could be incorporated into a body without defor-
mation during firing. 9 As a mixture of paraffin and carnauba wax
was found satisfactory for cold molding and in addition possessed
sufficient hardness to furnish the necessary molded strength, this
combination of materials was chosen for the binder. 10

9 W. J. Scott Patent 1,847,102, "Ceramic Material," March 1, 1932. W. J. Scott
Patent 1,977,698, "Ceramic Material and Method of Making the Same," October 23,

10 L. I. Shaw and W. J. Scott Patent 1,847,197, "Ceramic Material and Method of
Making the Same," March 1, 1932.

12 A. G. Johnson and L. I. Shaw, "Ceramics in the Telephone," Industrial and
Engineering Chemistry, Vol. 27, pp. 1326-1332, November, 1935.

BSTJ 18: 2. April 1939: Some Ceramic Manufacturing Developments of the Western Electric Company. (Johnson, A.G.; Shaw, L.I.)


Dimensions —The dimensions and outline diagrams are given in Figures 1 and 2, The overall di¬
mensions are:

Mounting —The 301A emplo
Electric 143B or similar socket
the base terminals are shown in

The tube should be mounted in a ^rtical position with the base end down. There should be
a free circulation of air^Sl^ngWhe tube. No object should touch the glass bulb.

iin thrust type base suitable for use in a Western
ions and the arrangement of electrode connections to

The thisppube is designed to operate on a voltage basis from an alternating-current

supply. The vd^taWshould be maintained to within 5% of its rated value (5.0 volts). Operation

of the filament at a voltage above the upper limit will definitely reduce the life of the tube while a
decrease in voltage below the lower limit may cause immediate failure.

Sufficient time must always be allowed for the filament temperature to reach its normal operat¬
ing value before the anode potential is applied. If filament circuits with good regulation are
used, this time is 30 seconds. If the tube is operated at ambient temperatures below 20 ° C., a
longer period of time is required for the purpose of bringing the mercury vapor pressure to a satis¬
factory operating value. The minimum filament warming time as a function of ambient tempera¬
ture is shown in figure 3 .

For proper distribution of the mercury a period of 10 to 15 minutes filament warming time
should be allowed when the tube is used for the first time or if it has been reinserted in the apparatus
after having been removed.

Maximum operating ambient temperature range. . .
Recommended operating ambient temperature range

The anode-cathode potential drop is substantially independent of the plate current. The
exact value varies from tube to tube and during the life of a given tube. Within the specified
ambient temperature range and plate current range, it may vary from 5 to 25 volts.

The anode-cathode drop as a function of temperature is shown on fig. 4 for a typical 301A tube
after reaching temperature equilibrium and when passing the rated plate current.

The maximum permissible peak plate current (L 0 ampere) is a limitation on the instantaneous
value that the tube can carry safely in the direction in which it is designed to conduct and should
not be exceeded. The maximum direct load current is not fixed but will depend upon the wave
form required by the load and filter circuit.

The maximum permissible peak potential between electrodes (1800 volts) is a limitation on
the instantaneous value that the tube can stand safely. If it is exceeded, an arc-back may result
which will injure the tube. The maximum direct potential available is not fixed but will depend
upon the type of circuit used.

301x4 vacuum tubes may be operated in parallel if some provision is made to insure a proper
division of the load current. Current dividing reactors or ballasting resistors in series with each
anode, may be used for this purpose. The size of the reactors or resistors depends upon the circuit
design.

In most cases the termination of the useful life of the 301A tube is due to the loss of filament
activity. This causes the tube to fail by arcing between the electrodes. Failures of this kind
should be safeguarded by proper fuse protection to prevent injury to other tubes in the circuit and
to the auxiliary equipment.

Typical Rectifier Circuits —The 301A vacuum tube may be used in any standard high vacuum
rectifier circuit subject to its current, voltage and temperature limitations. Typical circuits are
shown below. The approximate direct output current and voltage for each type of rectifier circuit
where tubes are operated at maximum permissible plate current and inverse voltage are given in
Table 1. The values listed are average values of the pulsating current and voltage for an
unfiltered circuit.

CORRESPONDING AMEilENT TEMPERATURE
AFTER REACHING TEMPERATURE EQUILIBRIUM
IN DEGREES CENTIGRADE

A. development of Bell Telephone Laboratories, Incorporated,
the research laboratories of the American Telephone and Tele¬
graph Company and the Western Electric Company

This tube was designed primarily for use as an audio-frequency amplifier or modulator; or as
a radio-frequency oscillator or amplifier.

Dimensions —Dimensions and outline diagrams are shown in Figures 1 and 2 and are:

Mounting— Large four-pin bayonet base for use in a W. E. 113A or similar socket, for either
vertical or horizontal mounting. If mounted horizontally the plane of the filament, which is
indicated in Figure 2, should be vertical.

Characteristics —Performance data given below are based upon a typical set of conditions.
Variations can be expected with different circuits and tubes.

Figures 3 and 4 give the static characteristics of a typical tube plotted against grid and plate
voltages.

Average Characteristics at 1600 volts direct plate potential and minus 160 volts grid bias,
I b - .167 ampere.

The above are maximum ratings which do not apply simultaneously but depend on the
type of service as specified below.

Mechanical— Figures 1 and 2 show the overall dimensions and basing arrangement for the
tube.

The tubes should not be subjected to mechanical shock or excessive vibration. Mechanical
vibration may cause breakage of the thoriated tungsten filaments.

A free circulation of air must be provided to insure adequate cooling of the glass during operation.

Electrical—Overload protection should always be provided for the plate circuit. A suitable
fuse or circuit breaker should remove the plate voltage if the plate current exceeds 425 milliamperes.
Although the tube is sufficiently rugged to withstand momentary overloads, a prolonged overload
caused by inefficient adjustment of the circuit, may damage the tube. When adjusting a new
circuit, reduced plate voltage or a series resistance of 1000 to 5000 ohms in the plate circuit should
be used until it is operating properly.

The filament should always be operated at the rated voltage, measured at the tube terminals.
A 5 % decrease in filament voltage reduces the thermionic emission approximately 25%. Either
direct or alternating current may be used for heating the filament. If direct current is used, the
plate and grid circuit returns should be connected to the negative filament terminal. If alternating
current is used, the circuit returns should be connected to the center tap of the filament heating
transformer winding or to the center tap of a resistor placed between the filament terminals.
A resistance of 30 to 40 ohms of ten watt rating is suitable.

In cases where severe and prolonged overload has temporarily impaired the electronic emission
of the filament, the activity may be restored by operating the filament, with the plate and grid
voltages off, 30% above normal voltage for 10 minutes followed by a longer period at normal voltage.

Grid bias may be obtained from the drop across a resistance in the plate current return
or from a battery or rectifier supply.

Plate dissipation allowable for this type of service is generally lower than is safe for other
uses since the energy is dissipated in the plate in smaller areas due to relatively high voltage
drop in the tube.

The plate dissipation is equal to the plate voltage multiplied by the normal plate current.
Performance data are based upon the use of a resistance load. Undistorted output is calculated
on the basis of 5% second harmonic distortion.

Class B—Grid bias practically at cut-off and grid driving voltage higher than the bias.

Two tubes may be used in a balanced circuit. An adequate driving stage and an input
transformer with good regulation must be used so that the grid current drawn during positive
grid swings does not produce appreciable distortion. The output transformer must transform
the load impedance to the proper value for the tubes used. The power output obtainable will
be determined by the quality of the transformer used and the amount of distortion which can
be tolerated. The grid bias must be held constant and therefore cannot be obtained by grid
leak or series resistor methods. A battery or other source having good regulation is necessary.

The power required of a modulator for complete modulation of a Class C amplifier is
one-half the direct power input to the plates of the Class C amplifier.

The Class B radio-frequency amplifier is used to amplify a modulated radio-frequency
carrier wave without appreciable distortion. It operates similarly to the Class B audio
amplifier except that a single tube may be used, the tuned output circuit serving to preserve
the wave shape. The push-pull circuit, however, eliminates the even order harmonics and
thus increases the efficiency slightly.

This type of operation is suitable for telegraphy, or the production of a continuous flow
of radio-frequency power for purposes other than communication.

This type of operation is for use when the modulating voltage is superimposed on the
plate supply voltage and to obtain good quality the output power should vary as the square of
the plate voltage. For complete or 100% modulation, the plate voltage varies from zero to twice
the applied direct value during a cycle of the audio frequency. With no modulation applied,
the plate voltage is, of course, the direct value and the carrier power output is one-fourth of
the peak power output under 100% modulation. In this case, since the plate voltage varies
with modulation, the direct value must be rated lower than for other types of operation.

The frequency limits specified under maximum ratings are based on the tube being used as
an oscillator. The tube may be used at full rating up to 1.5 megacycles. When operating at higher
frequencies, the dielectric losses, charging currents and lead-in heating are increased greatly.
The plate voltage and hence plate dissipation must be reduced to values specified for the upper
frequency limit and for frequencies between these two limits the plate voltage should be propor¬
tionately reduced.

1-J-3G-35C the research laboratories of the American Telephone ami Tele* V. T. DATA SHEET 308B

BELL SYSTEM PRACTICES
Transmission Engineering and Data
Electron Tube Data

The 310A is an indirectly heated cathode type pentode having a separate
suppressor grid connection. It is intended for use in audio, carrier and radio-
frequency voltage amplifiers, oscillators or modulators.

^Operation with the heater at 9.0 volts is permissible
only when such voltage is regulated to ± 1.0# or better.

The 310B Is an indirectly heated cathode type pentode haying a separate
suppressor grid connection. It is intended for use in audio, carrier and radio¬
frequency voltage amplifiers, oscillators or modulators. This tube, except for
having special design features to minimize microphonic noise and hum and having
an appreciably lower maximum heater-cathode voltage rating, is identical to the
310A.

BELL SYSTEM PRACTICES
TRANSMISSION ENGINEERING AND DATA
ELECTRON TUBE DATA

The 311A is a suppressor grid power pentode having an indirectly heated cathode.
It is designed for use as an audio, carrier or radio-frequency amplifier.

A development of Bell Telephone Laboratories* the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Company

The 3113 is a suppressor grid power pentode having an indirectly heated
cathode. It is designed for use as an audio, carrier or radio-frequency amplifier.

Dimensions and pin connections shown in outline drawing on Page 4
Maximum Ratings, Absolute System (Note 2)

Screen Grid Voltage. .
Plate Dissipation. . .
Screen Grid Dissipation
Cathode Current....
Heater-Cathode Voltage

TYPICAL OPERATING CONDITIONS AND CHARACTERISTICS
Single Title Amplifier - Class A

Note 2: In the "Absolute System" the maximum ratings specified are limiting
values above which the serviceability of the device may be impaired
from the viewpoint of life and satisfactory performance. Maximum
ratings, as such, do not constitute a set of operating conditions
and all values may not, therefore, be attained simultaneously.

BELL SYSTEM PRACTICES
Transmission Engineering and Data
Vacuum Tube Data

Classification —Double gap, cold cathode, gas-filled tube for use as a relay, rectifier or voltage
regulator in special circuits.

The elements of the 313A tube consist of two similar control electrodes and one anode. The
conduction path between the control electrodes is known as the control gap. The conduction path
between either control electrode and the anode is known as the main gap.

The glass bulb has been given an opaque coating so that the discharge is not visible while the
tube is operating. In the photograph at the right the coating has been removed to show the tube
elements.

Dimensions —The dimensions and outline diagrams are given in Figs. 1 and 2. The overall
dimensions are:

Mounting —The 313A vacuum tube employs a standard four-pin thrust base suitable for use in
a Western Electric 143B or similar socket. The arrangement of electrode connections to the base
terminals is shown in Fig. 2.

The “maximum peak control-electrode current” is the maximum value of current which may
be drawn from either control electrode when it is acting as a cathode.

The “maximum average control-electrode current” is the maximum value of current (averaged
over 1 second' 1 which may be drawn from either control electrode when it is acting as a cathode.

The “maximum peak reverse current in the main gap” is the maximum value of current which
may be drawn from the anode in the reverse direction, that is when it is acting as a cathode. The
reverse current rating is intended for use in designing rectifier circuits and is the maximum inverse
current which it is permissible to draw- from the tube in such circuits.

The “control gap breakdown voltage” is the potential required to initiate ionization, thereby
starting conduction in the control gap. Once ionization has occurred the potential across the gap
will be reduced to the “control gap sustaining voltage” and will be approximately independent
of the current. It is this property of the tube which enables it to be used as a voltage regulator.

The “main gap breakdown voltage” is the potential required to start conduction in the main
gap w'hen no ionization is occurring in the control gap. After breakdown, conduction will take
place at the “main gap sustaining voltage” and will be practically independent of current.

The “main gap sustaining voltage” is substantially independent of current when the current
passes through the tube in the forward direction. When the current passes through the main gap
in the reverse direction the sustaining voltage increases rapidly with increasing current. It is this
asymmetry in the properties of the main gap of the 313A tube wdiich enable it to be used as a
rectifier. The current voltage characteristics of the main gap of a typical 313A tube in both forw r ard
and reverse directions as shown in Fig. 3. This curve was obtained with a cathode ray oscillograph.

When the anode potential is maintained at a value intermediate between the “main gap break¬
down and sustaining voltages” the passage of a small amount of current in the control gap will
produce ionization sufficient to initiate conduction in the main gap. It is this property of the tube
which enables it to be used as a relay. The amount of current m the control gap required to initiate
conduction in the main gap is known as the transfer current. This quantity varies considerably
from tube to tube and during the life of a given tube but will in general be less than o microamperes
and usually only a few tenths of a microampere.

The deionization time is the time during which the voltage must be removed from the tube in
order that the discharge shall not be reestablished when the voltage is restored. This time increases
with increasing applied voltage and wdth increasing current through the tube before the deioniza¬
tion period. This rate of increase of deionization time is such that the tube will not deionize wdth
a 60 cycle sine wave main gap voltage if the load is inductive or if the peak voltage is near the
main gap breakdown voltage or the current near the maximum rated value.

The “transfer time” is the time during which the control gap must be energized in order that
the discharge may transfer to the main gap. It depends upon the amount of current flowing in
the control gap and on the main gap voltage. For a control gap current of 10 microamperes the
“transfer time” is approximately 200 microseconds.

Circuit A shows a circuit using the control gap of the 313A as a voltage regulator.

Circuit B shows a circuit using the 313A as a relay. The anode voltage should be intermediate
between the main gap breakdown and sustaining voltages and the control anode may be biased
at any desired potential less than the control gap sustaining voltage. The resistance R, in the
control anode circuit should be of the order of 100,000 ohms. This circuit possesses a “lock-in”
feature, since the anode potential must be removed momentarily to restore the tube to a non¬
conducting condition. When supplied from alternating current this circuit does not possess a
“lock-in M feature unless the frequency of the supply voltage is so high that the tube is not allowed
a sufficient interval to deionize.

Circuit C shows a circuit using the 313A as a rectifier. The rectifying properties of the main
gap are used but the control gap should be connected into the circuit as indicated through a high
resistance. This will cause conduction in the forward direction to begin at a voltage much below
the main gap breakdown voltage. It is important to note that as a rectifier the 313A tube possesses
a unique property not common to other rectifiers in that its impedance is infinite for voltages
below the breakdown voltage. In many applications that is of importance since the tube may be
used to pass current at the higher potentials without placing a bridge across the line for signals of
lower voltage.

1-J-36-73C the research laboratories of the American Telephone and Tele- V T. DATA SHEET 313A

The 313C is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

This tube contains a small amount of krypton-85 gas which is a by-product
radioactive material. The amount of krypton-85 is less than five microcuries, which
is too small an amount to require any special care in use.

Atomic Energy Commission regulations require that the individual tube carton
for tubes containing by-product radioactive material be appropriately marked. The
marking includes the statement that tube disposal should be in approved manner.

Approved instructions for disposal of tubes containing krypton-85 are as
follows;

Tubes to be disposed of should be broken or crushed in a well
ventilated place releasing any resulting vapors to the outside
atmosphere. The residual broken or crushed tubes should be dis¬
posed of in a normal public trash disposal system. Tubes should be
disposed of at a rate of not more than 100 each week from any one
location. Avoid breathing vapors from broken tubes.

Note l: In the ''Absolute System 1 ' the maximum ratings specified are limiting values above which the
serviceability of the device may be impaired from the viewpoint of life and satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: Sufficient resistance must be used in series with the tube to assure that the electrode
currents do not exceed the maximum rated values.

Note 3: Limits apply immediately after tube has conducted current. If tube has been idle, these
values initially may be as much as 3 volts higher or lower.

Note 4: with 15 volts overvoltage (15 volts above starter breakdown voltage) with tube in total
darkness.

Note 5: Negative anode voltage applied through 3000 ohms. Starter connected to anode through
100,000 ohms.

A development of Bell Telephone Laboratories, the research laboratories of the American Telephone

The 313CA is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

Starter Voltage Drop at 20 milliampere
Anode Voltage Drop at 20 milliamperes

This tube contains a small amount of krypton-85 gas which is a by-product
radioactive material. The amount of brypton-85 is less than five microcuries, which
is too small an amount to require any special care in use.

Atomic Energy Commission regulations require that the individual tube carton
for tubes containing by-product radioactive material be appropriately marked. The
marking includes the statement that tube disposal should be in approved manner.

Approved instructions for disposal of tubes containing krypton-85 are as
follows;

Tubes to be disposed of should be broken or crushed in a well
ventilated place releasing any resulting vapors to the outside
atmosphere. The residual broken or crushed tubes should be dis¬
posed cf in a normal public trash disposal system. Tubes should be
disposed of at a rate of not more than 100 each week from any one
location. Avoid breathing vapors from broken tubes.

Note 1: In the "Absolute System" the maximum ratings specified are limiting values above which the
serviceability of the device may be impaired from the viewpoint of life and satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: Sufficient resistance must be used in series with the tube to assure that, the electrode
currents do not exceed the maximum rated values.

Note 3: Limits apply immediately after tube has conducted current. If tube has been idle, these
values initially may be as much as 3 volts higher or lower.

Note 4: With 15 volts overvoltage (15 volts above starter breakdown voltage) with tube in total
darkness.

Note 5: Negative anode voltage applied through 8000 ohms. Starter connected to anode through 100,000
ohms.

The 313CB is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

Note 1: In the "Absolute System" the maximum ratings specified are limiting values above which the
serviceability of the device mav be impaired from the viewpoint of life ml satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: Sufficient resistance must be used in series with the tube to assure that the electrode
currents do not exceed the maximum rated values.

Note 3: Limits apply immediately after tube has conducted current. If tube has been idle, these
values initially may be as much as 3 volts higher or lower.

Note 4: With 15 volts overvoltage (15 volts above starter breakdown voltage) with tube in total
darkness.

Negative anode voltage applied through 8000 ohms. Starter connected to anode through 100,000
ohms.

The 313CC is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

Note 1: In the ’’Absolute System” the maximum ratings specified are limiting values above which the
serviceability of the device may be impaired from the viewpoint of life and satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: Sufficient resistance must be used in series with the tube to assure that the electrode
currents do not exceed the maximum rated values.

Note 3: Limits apply immediately after tube has conducted current. If tube has been idle, these
values initially may be as much as 3 volts higher or lower.

Note 4: With 15 volts overvoltage (15 volts above starter breakdown voltage) with tube in total
darkness.

Note 5: Negative anode voltage applied through 8000 ohms, starter connected to anode through 100,000
ohms.

A development of Bell Telephone Laboratories, the research ianoratories of the American Telephone
and Telegraph Company and the Western Electric Company.

The 315A is a half-wave, mercury-vapor rectifier tube for use in high-voltage rectifier
circuits.

Condensed Mercury Temperature 20 to 55 C
Condensed Mercury Temperature 20 to 65 C

Mounting . . . This tube should be mounted in a vertical position only, with the

base end down. Sufficient clearance should be maintained around
the tube to insure free air circulation.

el ectrode^y^cury-vapor and gas-filled thyratrcn with a
eristic. This tube is designed for use in regulated

2bb“l°0 volts;TEg=40C;grid overvoltage-5 volts
Ebb*100 volts;THg*80C;grid overvcltage=25 volts

Critical Grid Current at 220 Anode Volts ....
Change in Critical Grid Voltage at

Equilibrium Condensed Mercury Temperature
Rise above Ambient, Approximate

1. For starting conditions only. Equilibrium operation is limited to +20 c
minimum condensed mercury temperature.

2. Deionization time decreases with an increase in negative grid voltage or
with a decrease in (a) condensed mercury temperature (THg), (b) grid resis¬
tance or (c) anode current immediately preceding the end oi conduction.

3. Ionization time decreases with an increase in (a) anode voltage, (b) con¬
densed mercury temperature (TEg) or (c) grid overvoltage. Grid overvoltage
is defined as the magnitude by which the applied voltage exceeds, in a
positive direction, the critical grid voltage value. Critical grid voltage
is the instantaneous value of grid voltage at the time when anode current
starts to flow.

TYPICAL CONTROL CHARCTER1STICS.
SHADED AREA SHOWS RANGE OF CHAR¬
ACTERISTICS, CONDENSED MERCURY
TEMPERATURE -55°C. TO +80°C.

A development of Bell Telephone Laboratories, the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Company.

BELL SYSTEM PRACTICES
Transmission Engineering and Data
Vacuum Tube Data

The 327A vacuum tube is designed to supply direct current from an alternating-current supply
in power systems for battery charging and for other purposes.

Dimensions —The dimensions and outline diagram are given in Figure 1. The overall dimen¬

Mounting-— This tube employs a 3 connection, skirted medium screw base. Overall dimensions
are shown in Figure 1.

The tube may be mounted either in a vertical or a horizontal position. There should be a free
circulation of air around the tube. No object should touch the glass bulb.

The filament of this tube is designed to operate on a voltage basis from an alternating-current
supply. The voltage should be maintained to within 10% of its rated value (2.0 volts). Operation
of the filament outside of these limits may cause the tube to become inoperative. Filament and
plate voltage may be applied to the tube simultaneously.

The anode-cathode potential drop is substantially independent of the plate current. The
exact value may vary from tube to tube and during the life of a given tube over the range from 5 to
10 volts.

The ignition voltage is the voltage required to start conduction within the tube. In a-c. circuits
this is a function of frequency, increasing as the frequency increases. The values are given for
60 cycles since this frequency will be most generally encountered in circuit design.

The maximum permissible peak plate current (6 amperes) is a limitation on the instantaneous
value that the tube can carry safely in the direction in which it is designed to conduct and should
not be exceeded. The maximum average load current (2 amperes) is the maximum direct output
current which may be obtained from a half-wave circuit using one tube. A full-wave circuit using
two tubes will supply a maximum of 4 amperes.

The maximum permissible peak inverse potential (275 volts) is a limitation on the instan¬
taneous value that the tube can stand safely. If it is exceeded, an arc-back may result which may
injure the tube. All circuits should be adequately fused to prevent injury to the equipment in
event of arc-back due to line surges. The maximum output voltage obtainable in either the half¬
wave or full-wave circuit is approximately 75 volts.

327A vacuum tubes may be operated in parallel if some provision is made to insure a proper
division of the load current. Current dividing reactors or ballasting resistors in series with each
anode, may be used for this purpose. The size of the reactors or resistors depends upon the circuit
design.

the research laboratories of the American Telephone and Tele- V. T. DATA SHEET 327A

Classification—Voltage-amplifier, suppressor-grid pentode with indirectly heated
cathode

The electrical characteristics of the 328A tube are identical with those of the 310A tube except
for the heater voltage and current.

This tube is intended primarily for use in audio, carrier and radio-frequency voltage amplifiers,
oscillators or modulators. The connection for the suppressor grid has been brought out to an external
terminal, thus making the tube more flexible in its applications.

Dimensions— Dimensions, outline diagrams of the tube and base, and the arrangement of the
electrode connections to the base terminals are shown in Figures 1 and 2.

Base— Small, six-pin thrust type with pins silver-plated. A small, metal cap control-grid terminal
is located at the top of the bulb.

Socket —Standard, six-contact type, preferably provided with silver-plated contacts such as the
Western Electric 144B socket.

The heater element of this tube is designed to operate on a voltage basis and should be operated at
as near the rated voltage as is practicable.

Cathode Connection —Preferably direct to the heater. If voltage must be applied between
the cathode and heater, it should not exceed 150 volts.

Characteristics— Plate current and screen-grid current characteristics of a typical 328A tube are
shown in Figures 3 and 4, respectively, as functions of control-grid voltage for several values of
screen-grid and plate voltage and zero suppressor-grid voltage. The screen-grid voltage for these
characteristics is equal to the plate voltage. Corresponding amplification factor, plate resistance,
and transconductance characteristics are given in Figures 5, 6 and 7. Plate current and screen-
grid current characteristics as functions of plate voltage are given in Figures 8 and 9, respectively,
for several values of control-grid voltage, a screen-grid voltage of 135 volts, and zero suppressor-
grid voltage. Corresponding amplification factor, plate resistance, and transconductance charac¬
teristics are shown in Figures 10, 11 and 12. Plate current, screen-grid current, plate resistance,
and transconductance characteristics are shown in Figures 13, 14, 15 and 16 as functions of plate
voltage for several values of suppressor-grid voltage, a screen-grid voltage of 135 volts, and a control-
grid voltage of —3 volts. These last characteristics are of particular interest in modulator applica¬
tions where separate inputs are applied to the control and suppressor grids.

Maximum cathode current (screen-grid current plus plate current) 10 milliamperes
Maximum screen-gnd current. 2,5 milliamperes

Operating Conditions and Output —Nominal performance data are given in the table below
for a number of typical operating conditions. Less severe operating conditions should be selected
in preference to maximum operating conditions wherever possible. The life of the tube at maximum
conditions may be shorter than at less severe conditions.

The performance data include the fundamental voltage or power output for the indicated
values of load resistance and input voltage, and the maximum second and third harmonic levels
for input voltages no greater than the indicated values. The voltage output is given in peak volts,
the power output in milliwatts, and the harmonic levels in decibels below the fundamental.

Curves showing the fundamental power and voltage output and the second and third harmonic
levels as functions of input voltage for a number of values of load resistance and a typical operating
condition are given in Figures 17, 18, 19 and 20.

THIRD HARMONIC IN DB SECOND HARMONIC IN DB FUNDAMENTAL OUTPUT FUNDAMENTAL POWER OUTPUT

The 328A is an indirectly heated cathode type pentode having a separate
suppressor grid connection. It is intended for in use in audio, carrier and radio¬
frequency voltage amplifiers, oscillators or modulators. This tube, except for
having a different heater voltage and current rating, is identical to the 310A
tube.

Screen Grid Voltage . .
Plate Dissipation . . .
Screen Grid Dissipation
Cathode Current . . .
Heater-Cathode Voltage

Classification—Low-power, suppressor-grid pentodes with indirectly heated cathodes

These tubes are intended primarily for use as audio, carrier or radio-frequency power amplifiers
where power outputs of approximately two watts are required and where the plate voltage is not in
excess of 180 volts. The suppressor grid is permanently connected to the cathode within the tube.

Dimensions and Connections— Dimensions, outline diagrams of the tubes and bases, and the
arrangement of the electrode connections to the base terminals are shown in Figures 1 and 2.

Base and Mounting —These vacuum tubes employ small five-pin thrust type bases with silver
plated pins. They are adapted for use in standard five-contact type sockets, preferably those pro¬
vided with silver-plated contacts such as the Western Electric 141A socket. A small metal cap
control-grid terminal is located at the top of the bulb.

The heaters should be operated on a voltage basis and at as near the rated voltage as
practicable.

Characteristics—Figures 8 and 4 respectively, show plate current and screen-grid current as
functions of control-grid voltage for several values of screen and plate voltage. In all curves the
plate voltage is equal to the screen voltage. Amplification factor, plate resistance and transcon-
ductance curves for the conditions corresponding to those of Figures 3 and 4 are given respectively
in Figures 5, 6 and 7.

Plate current and screen-grid current are shown as functions of plate voltage in Figures 8 and
9 respectively, for a screen-grid voltage of 135 volts and for several values of control-grid voltage.
Corresponding curves for amplification factor, plate resistance and transconductance are given in
Figures 10, 11 and 12 respectively.

Curves showing the fundamental power output and the second and third harmonic levels as
functions of input voltage for a number of values of load resistance for typical operating conditions
are given in Figures 13, 14 and 15 respectively.

Maximum cathode current (plate current plus screen-grid current) 60 milliamperes
Maximum direct screen-grid current . 12 milliamperes

Operating Conditions and Output — Nominal performance data are given in the table
on page 3 for a number of typical operating conditions. Less severe operating conditions should be
selected in preference to the maximum conditions wherever possible. The life of the tube at maxi¬
mum conditions will be shorter than at the less severe conditions.

The performance data include the fundamental power output for the indicated values of load
resistance and input voltage, and the maximum second and third harmonic levels for input voltages
not exceeding the indicated values. Under certain conditions the maximum second harmonic level
occurs at a lower input voltage than that given in the table. The power output is given in watts,
and the harmonic levels in decibels below the fundamental.

The 333A is a three-electrode, inert-gas-filled, cold cathode tube for use in relay,
voltage regulator, or rectifier circuits. This tube is especially suitable for use in control
circuits such as in triggering, counting, or switching apparatus.

Peak Anode Voltage
Average Cathode Current
Average Life, approximate
Transfer Current

Required Transfer Current at 130 Anode Volts (D.C.)
Deionization Time, approximate

¥ Limits apply immediately after tube has conducted current. If tube has been idle,
these values initially may be as much as 3 volts higher or lower.

Negative anode voltage applied through S,000 ohms. Starter connected to anode
through 100,000 ohms.

The 336A is a suppressor grid, power penthode with an indirectly heated cathode.
It is designed for use as an audio-frequency power amplifier in Class A x and ABi

BELL SYSTEM PRACTICES
Transmission Engineering and Dat
Electron Tube Data

The 337A is a variable-mu pentode of the unipotential cathode type* The sup¬
pressor grid is connected to a separate base pin to provide flexibility in usage.
This tube is designed for use as an audio, carrier or radio-frequency amplifier,
oscillator or modulator.

It is primarily a rectifier of J^w internal impedance whose conduction cycle is determined by
the relative instantaneous grid aitd abode potentials. It is intended for use in special circuits as a
relay or trigger-action device. A f&w^pf its other possible uses are: as a controlled-frequency
oscillator giving a squar^wa^|ornlSA a voltmeter or volume level-indicator, as a source of
sweep-voltage for a linear tm^e^^ oj^as a variable-voltage rectifier.

Mounting—This vacuum tube employs a standard five-pin thrust type base suitable for use in
a Western Electric 141A or similar socket. The arrangement of electrode connections to the base
terminals is shown in Figure 2.

It may be mounted in either a vertical or horizontal position, although the vertical position
is preferable.

The heater element of this tube is designed to operate on a voltage basis from a direct or
alternating current supply. The voltage should be maintained to within 5% of its rated value
(10 volts). Operation of the heater element above the upper limit will definitely reduce the life
of the tube, while a decrease below the lower limit may cause immediate failure.

Sufficient time should always be allowed for the cathode temperature to reach its normal
operating value before anode current is drawn. Failure to allow sufficient time may result in
immediate failure.

The characteristics of the 338A tube are such that, for any given anode potential, there is a
critical grid potential. If the grid is held more negative than this value and the tube is non-con¬
ducting, the anode current will remain zero. If it is made less negative, the current will assume a
value determined by the applied potential and the resistance in the anode circuit. To extinguish
the discharge and return the current to zero, the positive anode potential must be removed.
When current is flowing a visible discharge occurs in the tube. Under this condition, the tube
voltage drop is practically independent of the value of both the anode current and the grid
potential. A protective resistance should always be included in the circuit to limit the anode
current to the rated values. A typical curve relating the critical grid potential to the anode
potential is shown in Figure 3. This charactersitic may vary from tube to tube and during the
life of a given tube.

Sufficient resistance must always be included in the grid circuit to limit the negative grid po¬
tential to 10 volts when anode current is flowing. Failure to observe this precaution will result in
short tube life.

The tube may be used in a variety of circuits adapted to the application of thyratrons. Two
general types are common. One use of the tube is to produce a saw-toothed, current wave. The
circuit for this application is shown in Figure 4. The resistance R should, ordinarily, be at least
100,000 ohms, and the product RC (C in farads) approximately equal to the desired fundamental
period.

The second general use for the tube is as a relay device. In this application the anode may be
supplied from either alternating or direct current. When supplied from direct current, the circuit,
Figure 5, possesses a “lock-in” feature, since the anode potential must be removed momentarily
in order to restore the tube to the non-conducting condition. When supplied from alternating
current, the circuit possesses no “lock-in” feature, but the average anode current may be controlled
by the relative phase of grid and anode potentials. The schematic circuit for this application
is shown in Figure 6. Figure? is a simplified circuit employing a photoelectric cell in place of the
resistance, R, used in the phase shifting device in Figure 6. The photoelectric cell, however, is
equivalent to a variable resistance in the sense that the current passed will depend upon the
amount of light falling upon it.

A development of Bell Telephone Laboratories, Incorporated,
the research laboratories of the American Telephone and Tele¬
graph Company and the Western Electric Company

The 345A is a full-wave rectifier with indirectly heated cathodes. It is designed to
supply direct current from an alternating current source or to rectify radio-frequency
currents for feedback purposes in broadcast transmitters.

A development of Bell Telephone Laboratories, the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Comjwun

The 346 b is a three-electrode, inert-gas-filled, cold cathode tube for use
in relay, voltage regulator, or rectifier circuits. This tube is especially
suitable for use in control circuits such as in triggering, counting, or
switching apparatus.

Dimensions and pin connections shown in outline drawing on page 4
Note 1: Sufficient resistance must be used in series with the tube to
assure that the electrode currents do not exceed their maximum
rated values.

Note 2: Limits apply immediately after tube has conducted current. If the
tube has been idle, these values initially nay be as much as 3
volts higher or lower.

Note 3: With 15 volts starter overvoltage (15 volts above Starter Breakdown
Voltage) with tube in total darkness.

Note 4: Negative anode voltage applied through 8COO ohms. Starter connected
to anode through 100000 o hm s.

Western Electric cold cathode tubes contain a minute amount of radium bromide
which is a radioactive material. The amount in most types is too small to require
any special care in use, handling or disposal.

A few types contain a larger quantity of radium bromide in which the radium
approximates that found on a luminous watch dial. These types bear a red three-
bladed propeller-shaped symbol on the tube envelope. Instructions for handling
such tubes are given below and also in Bell System Practices for Central Office
maintenance.

Installations ordinarily require no precautions against radiation. However,
quantities of the tubes should not he so installed, or so stored outside the
shipping carton ; that they will he within a few inches of personnel or in proxi¬
mity uo photographic film for extended periods of time. For example, however, a
4-0-hour week exposure at about one (l) foot from a bank of 5CO tubes (covering
an area of 20 inches x 45 inches) is well within the accepted tolerance limits
for personnel. Reasonable care should be exercised in handling and disposal of
broken tubes. In general, attention should be given to the following:

(c) Use wet rag to pick up broken parts. Wrap broken parts in rag and tie
securely sc as to form a package. Thoroughly wash hands after disposal.

One or two tubes at a time may be disposed of with normal waste material.
Accumulation of tubes in one concentrated area of the place of final
disposition should be avoided.

A development of Bell Telephone laboratories, the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Company.

The 346C is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

This tube contains a small amount of krypton-85 gas which is a by-product
radioactive material. The amount of krypton-85 is less than five roicrocuries, which
is too small an amount to require any special care in use.

Atomic Energy Commission regulations require that the individual tube carton
for tubes containing by-product radioactive material be appropriately marked. The
marking includes the statement that tube disposal should be in approved manner.

Approved instructions for disposal of tubes containing krypton-85 are as
follows;

Tubes to be disposed of should be broken or crushed in a well
ventilated place releasing any resulting vapors to the outside
atmosphere. The residual broken or Crushed tubes should be dis¬
posed of in a normal public trash disposal system. Tubes should be
disposed of at a rate of not more than 100 each week from any one
location. Avoid breathing vapors from broken tubes.

Note 1: In the "Absolute System" the maximum ratings specified are limiting values above which the
serviceability of the device may be impaired from the viewpoint of life and satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: Sufficient resistance must be used in series with the tube to assure that the electrode
currents do not exceed their maximum rated values.

Note 3: Limits apply immediately after tube has conducted current. If the tube has been idle, these
values initially may be as much as 3 volts higher or lower.

Note 4; With 15 volts starter overvoltage (15 .volts above Starter Breakdown Voltage) with tube in
total darkness.

Note 5: Negative anode voltage applied through ROOO ohms. Starter connected to anode through 100,000
ohms.

BELL SYSTEM PRACTICES
TRANSMISSION ENGINEERING AND DATA
ELECTRON TUBE DATA

The 347A is a triode designed for use as an audio-frequency amplifier where exception¬
ally low tube noise is required. Special design features minimize both the microphonic
noise and the hum produced by a.c. operation of the heater.

Plate Voltage
Plate Dissipation
Plate Current
Heater-Cathode Voltage

TYPICAL OPERATING CONDITIONS AND CHARACTERISTICS-CLASS Ai AMPLIFIER

Under typical operating conditions, and
with the cathode of the tube connected to
the mid-point of the heater circuit, the
equivalent hum voltage in the grid circuit
will be less than 12 microvolts at the supply
frequenc\ r and less than 6.0 microvolts at

If the insulation leakage and capacitance be¬
tween the external grid and heater connec¬
tions are kept reasonably low, a resistance of
2 megohms may be used in the grid circuit
without materially affecting the hum level.

TRANSCONDUCTANCE IN MICROMHOS PLATE RESISTANCE IN OHMS AMPLIFICATION FACTOR

The 348 a is an indirectly heated cathode type pentode having a separate
suppressor grid connection. It is intended for use in audio, carrier and radio-
frequency voltage amplifiers, oscillators or modulators. It has special design
features to minimize microphonic noise and hum. This tube, except for having a
different base, top cap, heater voltage and current rating, is identical to the
310B,

Screen Grid Voltage . .
Plate Dissipation . «
Screen Grid Dissipation
Cathode Current ....
Heater-Cathode Voltage

The 349A is a suppressor grid, power pentode with an indirectly heated cathode.
It is designed for use as an audio-frequency power amplifier in Class A t and AB t
service.

Plate Voltage
Screen Grid Voltage
Plate Dissipation
Screen Grid Dissipation
Cathode Current
Heater-Cathode Voltage

The 350B is a beam power tetrode of the neater-cathode type. It is designed for use as an
audio-frequency amplifier or as a radio-frequency oscillator.

The 351A is an octal based full-wave rectifier with indirectly heated cathodes. It is
designed to supply direct current from an alternating current source or to rectify radio¬
frequency currents for feedback purposes in broadcast transmitters.

D-C Output Volts, Approximate, at Input to Filter
Total Effective Plate-Supply Impedance per Plate
Filter Input Condenser .

A development of Bell Telephone Laboratories, the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Company

The 352A tube comprises three distinct vacuum tube units which are independent of each
other except that sections of a single cathode structure supply electron emission for all three. Two
of these units are diodes. The other is a triode.

Applications—Diode detector, diode rectifier for automatic volume control voltage, and triode
audio-frequency amplifier. If desired the two diodes may be used for full-wave rectification or they
may be connected in parallel to provide a lower impedance half-wave rectifier. The former con¬
nection requires about twice as high an input voltage as the latter to give equal detector output.

Dimensions and Connections—Outline diagrams of the tube and base giving the dimensions
and the arrangement of the electrode connections to the base terminals are shown in Figures 1 and 2.

Base and Mounting—This tube employs a small six-pin thrust type base suitable for use in a
Western Electric 144B or similar socket. The base pins are silver plated. The triode grid terminal
is a small metal cap located at the top of the bulb.

The heater of this tube is designed to operate on a voltage basis and should be operated at
as near the rated voltage as practicable.

Cathode Connection —Where alternating heater voltage is used the cathode should pref¬
erably be connected directly to the mid-point of the heater transformer winding or to the mid¬
point of a low resistance connected across the heater terminals. For direct current operation the
cathode may be connected to either end of the heater. If voltage is applied between the heater
and cathode, it should be kept low and must not exceed 50 volts.

Triode Characteristics— Typical curves showing triode plate current as a function of grid
voltage for several values of plate voltage are shown in Figure 3. Corresponding amplification
factor, plate resistance and transconductance characteristics are given in Figures 4, 5 and 6 re-
spectivelv. Figure 7 show's plate current as a function of plate voltage for several values of grid
voltage.

Permissible operating plate and grid voltages are included within the area, ABCD, in Figure 3.
.Amplification factor, plate resistance, transconductance and performance data for a number of
tvpical operating conditions are given in the table. Recommended conditions or others of no
greater severity should be selected in preference to maximum conditions wherever possible. The
Fife of the tube at maximum operating conditions will be shorter than at less severe conditions.

In the last four columns of the table are given the fundamental power output, P m , in milliwatts,
the fundamental voltage output, E pm , in peak volts and the second and third harmonic levels, F 2m
and F im , in db below the fundamental, for the indicated values of load resistance. The peak
value of the sinusoidal input voltage, E gm , is numerically equal to the grid bias in each case.
Where the level of the third harmonic is lower than 45 db below the fundamental, its value may
be widely different from tube to tube. The values given represent a typical tube.

For a smaller input voltage, E g , the fundamental power and voltage outputs and the harmonic
levels are given approximately by the following relations:

Triode Microphonic Noise— With a plate voltage of 135 volts, a grid bias of -6 volts, and a
load resistance of 100,000 ohms, the mean microphonic noise output level of the triode section of
the tube, measured in a laboratory reference test set, is 45 db below 1 volt. The range of levels of
individual tubes extends from 20 to 60 db below 1 volt. Since microphonic noise depends on the
type and intensity of the mechanical disturbance which produces it, the values given here are useful
chiefly for comparison with the levels of other tubes which have been tested in the same way.

Diode Characteristics— The current-voltage characteristic of a single diode is shown in Figure
8. Rectification characteristics for a single diode are shown in Figure 9 for a number of values of
impressed alternating input voltage. Each of these characteristic curves gives the relation between
the direct voltage impressed on the diode plate and the average diode current as indicated by a
direct-current microammeter for a constant impressed alternating input voltage of the value speci¬
fied. Where the diode is used as a detector with the usual condenser-resistance circuit, the direct
component of the voltage developed across the resistance by any alternating-voltage input is given
by the intercept of the load line with the rectification characteristic corresponding to the input
voltage. Load lines for zero fixed bias are shown in Figure 9 for load resistance values of 0,25,
0,5 and 1.0 megohm.

The potential of each diode plate with respect to the cathode on the positive swing of the input
voltage should be limited to a maximum value of +10 volts.

A development of Bell Telephone Laboratories, Incorporated
1-J-39-61C the research laboratories of the American Telephone and Tele-

BELL SYSTEM PRACTICES
Transmission Engineering and Dat^
Electron Tube Data

The 353A is a three-electrode, inert-gas-filled, cold cathode tube for use in
relay, voltage regulator, or rectifier circuits. This tube is especially suitable
for use in control circuits such as in triggering, counting, or switching apparatus.

Note 3: Limits apply immediately after the tube has conducted current. If tube has been idle, these-
values initially may be as much as 3 volts higher or lower.

Note 4: With 15 volts starter overvoltage (15 volts above starter breakdown voltage) with tube in
total darkness.

Note 5: Negative anode voltage applied through 8000 ohms. Starter connected to anode through 100,000
ohms.

A development of Bell Telephone Laboratories, the research laboratories of the American Telephone
and Telegraph Company and the Western Electric Company.

1. Deionization time decreases with an increase in negative grid voltage
or with a decrease in (a) condensed mercury temperature (THg), (b) grid
resistance or (c) anode current immediately preceding the end of conduction.

2. Ionization time decreases with an increase in (a) anode voltage, (b) condensed
mercury temperature (THg) or (c) grid overvoltage. Grid overvoltage is defined
as the magnitude by which the applied voltage exceeds, in a positive direction,
the critical grid voltage value. Critical grid voltage is the instantaneous
value of grid voltage at the time when anode current starts to flow.

SHADED AREA SHOWS RANGE OF CHARACTERISTICS»
CONDENSED-MERCURY TEMPERATURE +30 # T0+70 # C

A development of Bell Telephone Laboratories, the research laboratories of the
American Telephone and Telegraph Company and the Western Electric Company*

Critical Grid Current at 220 Anode Volts .
Change in Critical Grid Voltage at

1. For starting conditions only. Equilibrium operation is limited to +2GC
minimum condensed mercury temperature.

2. Deionization time decreases with an increase in negative grid voltage
or with a decrease in (a) condensed mercury temperature (THg), (b) grid
resistance or (c) anode current immediately preceding the end of conduction.

3. Ionization time decreases with an increase ih (a) anode voltage, (b) condensed (
mercury temperature (THg) or (c) grid overvoltage. Grid overvoltage is
defined as the magnitude by which the applied voltage exceeds, in a positive
direction, the critical grid voltage value. Critical grid voltage is the
instantaneous value of grid voltage at the time when anode current starts to
flow.

TYPICAL CONTROL CHARACTERISTICS
SHADED AREA SHOWS RANGE OF CHARACTERISTICS
CONDENSED MERCURY TEMPERATURE - 55* TO + 80*C

The 357B is a three-electrode tube designed
for use as a radio-frequency amplifier or
oscillator, audio-frequency amplifier or
modulator. The anode is capable of dissi¬
pating 400 watts. The tube is cooled by radi¬
ation at frequencies below 40 megacycles.

Forced-air cooling of the envelope is neces¬
sary at higher frequencies. The tube is ca¬
pable of operating up to 100 megacycles at
maximum ratings and up to 150 megacycles
at reduced ratings. The cathode is a thori-
ated tungsten filament.

Required Air flow on Envelope
When Operated Above 40 Megacycles .
Maximum Incoming Air Temperature

1. Represents maximum usable cathode current for tube
as plate current plus grid current for any condition of
operation.

2. Radiation cooling is adequate ’when the tube is operated
below 40 megacycles and with a free circulation of air
around the tube. If operated in a confined space or at a
frequency above 40 megacycles, forced-air cooling is
necessary. Satisfactory air cooling will be obtained from
a blower delivering approximately 40 cubic feet of air
per minute from a 2-inch diameter nozzle. The nozzle
outlet should be placed approximately 3 inches from the

tube and directed toward the central point of the enve¬
lope, midway between the plate and grid terminals.

The plate terminal connector shall be of a design that
will readily conduct heat from the plate terminal.

3. This test is equivalent to a JAN-1A Pendulum Bump
Tester 15' test. The data given represent the maximum
capabilities of the tube without electrical potentials ap¬
plied and should not be construed to mean that the tube
is capable of withstanding an infinite number of shocks
of this magnitude.

MAXIMUM RATINGS AND TYPICAL OPERATING CONDITIONS
AUDIO-FREQUENCY POWER AMPLIFIER AND MODULATOR-CLASS B
MAXIMUM RATINGS, ABSOLUTE VALUES

D-C Grid Current, approximate
Driving Power, approximate 6 .
Power Output, approximate .

5. As high level modulator for 1000 watt transmitter. Total harmonics approxi¬
mately 1 . 5 % at full output.

PLATE MODULATED RADIO-FREQUENCY POWER AMPLIFIER—CLASS C TELEPHONY
Carrier conditions per tube for use with maximum modulation factor of 1.0

D-C Grid Current, approximate
Driving Power, approximate .
Power Output, approximate

Key-down conditions per tube without amplitude modulation 8
MAXIMUM RATINGS, ABSOLUTE VALUES

D-C Grid Current, approximate
Driving Power, approximate .
Power Output, approximate .

Maximum ratings apply up to 100 megacy cles.
The tube may be operated at higher frequen¬
cies provided the maximum values of plate
voltage and plate input are reduced according

to the tabulation below. Other maximum rat¬
ings are not affected. Forced-air cooling of the
envelope with an air flow of approximately
40 cfm is required at these frequencies.

8. Modulation essentially negative may be used if the positive peak of the
envelope does not exceed 115 per cent of its unmodulated value.

Base pin positions shatl be
held to tolerances such that
pins will fit a flat - plate
gauge having a thickness
of .250" with 2 holes of
.391" ± .0005“ dia. and
1 hole of .469'i 0005" dia
All holes shall be located
on a 1,938" ± .0005" dia
circle at specified centers.

The 358A is a two-electrode, inert-gas-filled, cold cathode tube designed to
provide a visual signal for telephone work. When the tube is conducting, a glow will
appear near the surface of the negative electrode. If a d.c. voltage supply is used
the negative polarity should be applied to the upper electrode. The upper electrode
terminal may be identified by the adjacent circular dot of contrasting color on the
base. When the tube is operating with an alternating voltage a glow will appear on
both electrodes.

This tube possesses a unique property not common to filamentary type lamps in
that its impedance is essentially infinite for voltages below breakdown. In some
applications this is an advantageous feature since the tube may be used to pass
current at*the higher potentials without placing a conducting path across the line
for signals of lower voltage.

Unlike filamentary type lamps the light output of this tube is proportional to
the current through the tube instead of varying as a power of this current. This
tube is well adapted to furnishing a visual signal from a varying voltage source.

Note 1: In the "Absolute System" the maximum ratings specified are limiting values above which the
serviceability of the device may be impaired from the viewpoint of life and satisfactory
performance. Maximum ratings, as such, do not constitute a set of operating conditions and
all values may not, therefore, be attained simultaneously.

Note 2: When the tube is operating from a direct current supply, the upper electrode shall be used
as the cathode.

The 359A is a three-electrode, inert-gas-filled, cold cathode tube for use
primarily as a relay in communication circuits. It is also suitable for use in
control circuits such as in triggering, counting or switching apparatus and as a
visual indicator. This tube, by reason of small size and provision for wiring
directly into the circuits, may be used to advantage in equipment having limited
space for components.

Peak Anode Voltage, Maximum
Average Cathode Current • •
Average Life, Approximate *

The 372A is a three-electrode, inert-gas-filled, cold cathode tube for use in relay,
voltage regulator, or rectifier circuits. This tube is especially suitable for use in control
circuits such as in triggering, counting, or switching apparatus.

* Limits apply immediately after tube has conducted current. If tube has been idle,
these values initially may be as much as 3 volts higher or lower.

Negative anode voltage applied through 8,000 ohms. Starter connected to anode
through 100,000 ohms.

The 373A is a filamentary type suppressor grid pentode. It is designed for use as an audio,
carrier or radio-frequency voltage amplifier, oscillator or modulator.

1. Pin #6 is connected internally to pin #5 and is approximately 3/32 inch shorter
than the other pins to minimize noise when changing tubes while in service.

Western Electric Tube Manual 1963


This index lists the information that forms a part of, or supplements this specification, and indicates the
authorized issues thereof.

PAGE 1 .ISSUE

HMIIIM

ISSUES AUTHORIZED ON ABOVE DATE

TITLE

Wiring Diagram

Cordin

a- No longer required

b—The D Series Bell System Practice of the same number shall be used until the BSRS is available,
c—Information in accordance with that currently authorized.

Bell Telephone Laboratories, Incorporated - Dept 5222

Printed in O.S.A

BSRS-353. 317
Page 2, Issue 3

1. GENERAL

1. 01 This specification covers the connections and cording for 592-type

telephone sets.

2. CONNECTIONS AND CORDING

2. 01 Connections for the 592-type telephone sets shall be in accordance
with drawing LA-540 264. •

2. 02 Cording for the 592-type telephone sets shall be in accordance with
drawing LA-540265.

CO-+Q333Z

p/ngep

notes :

/ - CONTACT SEQUENCE :

REMOVING HANDSET

/. cA Closes before de
z. e 3 opens
RESTORING HANDSET
/. fg CLOSES
2 de. OPENS BEFORE zb'.

2" FOR MANUAL SERVICE, REPLACE DIAL WITH APPARATUS

BLANK, AND GREEN LEAD FROM TERMINAL !Z CF TERMINAL
STRIP ASSEMBLY SHALL BE TRANSFERRED FROM (F)
TERMINAL TO (RR) TERMINAL AT NETWORK .

CONNECT TO TERMINAL
'F~ ON NETWORK. (.SEE -
NOTE 2)

PW

li:ll

MTS CORD {SEE TABLE
POP CONNECTIONS)

TERMINAL

STRIP

TERMINAL STRIP

cn microphone e

CONTROL UNIT ASSEMBLY

S 6 7 : 8 A '10 II 12 j!3

5) (c) c ) Lo) ro^ K3) to) ig) I) !

VIEW FROM TOP OP SET
LESS MICROPHONE (j CONTROL UNIT ASSEMBLY

* TERMINAL CN NETWORK

! telephone:

KEY T MTG~\

COLOR OF MOUNTING CORO CONDUCTORS TO TERMINALS ON MICROPHONE<1 CONTROL UNIT ASSEMBLY

I 1

SET

FEATURES' CORD

Bk 3K

'BAY BA-BL'BB-W

P-W \ G-Y RrBK ! / ! G '3R-G\R-G R-3L~R-Y | BR-R

12

■

BL

W i

1 bk 1

VAN UAL ! VIAL

i

_

Tjv2A-3 S92B-3

ON-OFF D/8F-3

3>

S I 6 7

S': 9 | 10 // iz\ IS ■ IS 17 \ 17 \ IS

19

20

2-! \

i RP !

r- ' r

.... L _

~ r

! ! I

i 1 J

MICROPHONE

VIEW PROM UNDER SIDE OP
M/CROPHONE tj CONTROL UNIT ASSEMBLY

NOTES:

A. (L FOR METHOD OF CONNECTING AND SOLDERING LEAD

WIRES TO CONTACT SPRINGS AND EYELET TYPE TERMINALS
REFER TO LA850M2-33, FIGS. 84 & 85A RESP.)

8. (L FOR METHOD OF WRAPPING AND SOLDERING LEADS TO
CONTACT SPRING TERMINALS REFER TO LA850112-37
FIG. ioi.;

C. ALL OTHER SOLDERING SHALL 8E PER KS524 METHOD C.

NOTES CONTINUED

D. ALL WIRES ARE LEADS OF INDIVIDUAL APPARATUS,
UNLESS DESIGNATED WITH ITEM NUMBERS.

E. ITEMS 5, 6, 24, 25, 26, 27,428 «=*» ARE
SPECIFIED IN STOCK LIST OF LP14A241

L DESIGNATES GUIDANCE INFORMATION

DIMENSIONS UP TO AND INCLUDING 72 INCHES EXPRESSED IN INCHES. *
NON-LIMITED DIMENSIONS. OTHER THAN SIZE OF RAW MATERIAL. SHALL'
■E HELD WITHIN FRACTIONAL DECIMAL

Dssui
4 CHI

UNDER SIDE, POT TO
R6REE WITH LP-HAi5+,
ISS.E. TERM STRIP TO
AGREE WITH if-J4A242,
I iSS+BK&W LEAPS
FROM EQUALIZER
WERE SHOWN CONNECTED
WITH CORD TIPS TO
SCREW TERMS. 20 & 2/

RESP. Of term strip

ON TOP SIDE,
Removed . resistor

DESIGNATED item 42,

afTWfCA/ SOLOe«

TEK MIS . Z 4 *

-T£/z*7. «r/?/p. por.

Eeads »*: Ey weed

SHO Wa/ PP.OF7

TERM*. Z RESP. ON

TOP S/DG OF TEPFJ.

ST/ZIP.

I CHANGED: SAI VIEW FROM

\T0P ETC. TERM. STRIP TO

I AGREE WITH IP-I4A242.

ISS. 4.

• ' ' ■ T.'

1

1

1

W.M

lEZMQB

mm

AS-

A-

s&/9/R/ee~rn

E /

CEO.

22L.

CH4NOC4 ' IHAIOMT *t£W
leaf/ f#ov re*M /a ro
•OM~ KEV £ FKO ht T tiKM
/♦ TO Off KfT -

m

CO - 164**1

*4*

ISSUE 4

CHAN CEO . IN V/EWEROm

• *0

592 TYRE
TELEPHONE
SETS

WIPING DIAGRAMS

WESTERN ELECTRIC CO. INC

ENGINEER OF MANUFACTURE

Bell Telephone
Laboratories. Inc

LA- 54 - 02 . 64 -

mm

* LEADS ARE EROM MICROPHONE
CONTROL UNIT ASSEMBLY.

S S-R

\

S-R .

w .

BK ■

VIAL TERMU)

SWITCH

HANDSET CORD

*■ BR-BK
BR-BK

* BR-BL

* BR-W

RINGER

MTS 'CORD
(SEE NOTE A )

NETWORK

W

W

BK

R

N

W

BL

R

G*

BR-R

S-Y

TERMINAL strip
ON MICROPHONE
C CONTROL UNIT

G

Y

R- BK
S-BR
G-Y
■ Z

R-W

BK

NOTE :

A THE MOUNTING CORD SHALL BE DRESSED TO
APPROACH AS NEARLY AS POSSIBLE THE
METHOD OF DRESSING AS SHOWN.

60 T

IDENTIFICATION NO.

DESCRIPTION

I REF DESIG

G*%lS0mde:ir\G AS \ c flJ

61

tiSSUE /

59

w/ K

STOCK LIST

SUPPLEMENTARY DRAWINGS

SIGNIFICANCE OF SYMBOLS AND ITEM NUMBER SUFFIXES

—PARTIAL ASSEMBLIES OR OTHER
DRAWINGS WITH STOCK LISTS
—FARTS SHIPPED LOOSE

ITEMS NOT SPECIFIED AS
• OR "D" PARTS IN ITEM COLUMN
ARE INDIVIDUAL ("A"l PARTS.

WHERE ITEMS HAVE REFERENCE DESIGNATIONS. THEY MAT BE
USED IN LIEU OF ITEM NUMBERS ON THE DELINEATION.'

✓ IN “RCO“ COLUMN OF STOCK LIST—QUANTITY AS REQUIRED

✓ IN “REQ" COLUMN OF SUPPLEMENTARY DWG LIST—DRAWING REQUIRKO
• DENOTES MANUFACTURE DISCONTINUED

■ DENOTES MANUFACTURE LIMITED
AS—OENOTES APPARATUS BOOK ORAWINOS

A-

CO- U-OS33Z

issue z

tifTSS

59 C TYPE
TEL SETS
COP DINS
DIAGRAM

WESTERN ELECTRIC CO. INC

ENGINEER OF MANUFACTURE

Bell Telephone

LABORATORIES. INC

DIMENSIONS UP TO AND INCLUDING 7E INCHES EXPRESSED IN INCHES.
NON-LIMITED DIMENSIONS. OTHER THAN SIZE OF RAW MATERIAL. SHALL
BE HELD WITHIN FRACTIONAL DECIMAL

3S

LA- 540 P 65 -

Telephone Sets - 592 Type - Connections and Cording