    [Public Adress Equipment PA-4-C]
    [From the U.S. Government Publishing Office, www.gpo.gov]

    ﻿NON-CIRCULATING
    WAR DEPARTMENT
    31 JANUARY 1944
    NTSU LlbrXAKY
    PUBLIC ADDRESS EQUIPMENT
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    WAR DEPARTMENT TECHNICAL MANUAL
    WAR DEPARTMENT TECHNICAL MANUAL TM 11-435
    PUBLIC ADDRESS EQUIPMENT PA-4-C
    WAR DEPARTMENT •	31 JANUARY 1944
    For sale by the Superintendent of Documents, Washington, D. C. United States Government Printing Office Washington: 1945
    WAR DEPARTMENT, Washington, 25, D. C., 31 January 1944
    TM 11-435, Public Address Equipment PA-4-C is published for the information and guidance of all concerned.
    [A.G. 3100.7 (13 Dec. 43).]
    By order of the Secretary of War:
    G. C. MARSHALL,
    Chief of Staff.
    Official :
    J. A. UL1O,
    Major General,
    The Adjutant General
    Distribution : X *
    (For explanation of symbols see FM 21-6.)

    Table of Contents
    SECTION I. Description	Paragraph	Page
    General............................. 1	1
    Components ......................... 2	1
    IL Installation and operation Preparation for use ......................... 3	5
    Operation .......................... 4	7
    III.	Functioning of parts General ...................................... 5	7
    IV.	Maintenance General ...................................... 6	11
    To remove the amplifier	chassis ... 7	11
    Tests ........r.................. 8	11
    V.	Supplementary data Table of replaceable parts ............... 9	16
    Manufacturers’ names and addresses 10	18
    List of Illustrations
    I'ig.No.	Title	Page
    1.	Public Address Equipment PA-4-C, components... 2
    2.	Public Address Equipment PA-4-C, assembled with Tripod M-230 and Microphone T-36-C............... 4
    3.	Public Address Equipment PA-4-C, in use as portable equipment ....................................... 6
    4.	Public Address Equipment PA-4-C, showing Microphone T-36-C in use (auditorium)....................... 8
    5.	Public Address Equipment PA-4-C, showing Microphone T-36-C in use (field)........................... 10
    6.	Amplifier BC-641-C, showing chassis and method of connecting batteries ........................ 12
    7.	Public Address Equipment PA-4-C in Case CS-91-C	14
    8.	Public Address Equipment PA-4-C, schematic diagram. 15
    iii
    DESTRUCTION NOTICE
    WHY —To prevent the enemy from using or salvaging this equipment for his benefit.
    WHEN—When ordered by your commander.
    HOW —1. Smash—Use sledges, axes, handaxes, pickaxes, hammers, crowbars, heavy tools, etc.
    2.	Cut—Use axes, handaxes, machete, etc.
    3.	Burn—Use gasoline, kerosene, oil, flamethrowers, incendiary grenades, etc.
    4.	Explosives—Use fire arms, grenades, TNT, etc.
    5.	Disposal—Bury in slit trenches, foxholes, other holes. Throw in streams. Scatter.
    USE ANYTHING IMMEDIATELY AVAILABLE FOR DESTRUCTION OF THIS EQUIPMENT.
    WHAT—1. Smash—Tubes, amplifier, loudspeaker, microphone, batteries and case.
    2.	Cut—Cords and shoulder harness.
    3.	Bend and/or Break—Tripod.
    4.	Burn—Instruction books, shoulder harness and wire.
    5.	Bury or scatter—Any or all of the above pieces after breaking.
    DESTROY EVERYTHING
    SAFETY NOTICE
    Plate potential of 135 volts is available in Public Address Equipment PA-4-C. Be careful, when installing “B” batteries, or adjusting or repairing this equipment, to avoid shocks which are always unpleasant and can be dangerous.
    iv
    Section 1 Description
    1.	GENERAL Public Address Equipment PA-4-C is a light-weight, portable public address system, to he used for the purpose of speech amplification in limited areas for mobile or stationary use. It has an undistorted output of two watts.
    2.	COMPONENTS
    a.	The components that make up Public Address Equipment PA-4-C are:
    Item	Quantity	Article	Dimensions in inches	It eight in lbs.
    *1 •X- o *3 *4	1	Amplifier BC-641-C 12	Battery BA-30; 4 installed; 8 spare 4	Battery BA-51 for Am- plifier BC-641-C; 2 installed, 2 spare 2 Sets Tubes, vacuum; complete, for Amplifier BC-641-C 1 Set (consisting of 1-— 1H4G and 1—1J6G) installed; 1 Set spare	8%x8i/4x3y16 Overall dimensions	7.0
    5 6	1	Case CS-91-C 2	Technical Manual for Public Address Equipment PA-4-C	19%xl0%x8%	11.0
    *7	1	Loudspeaker LS-6-C	14% long; 10% bell	6.0
    *8	1	Microphone T-36-C		.5
    *9	1	Shoulder Harness ST-39		.75
    *10	1	Tripod M-230-C	15 long (extended 53C)	1.75
    *NOTE: Items 1, 2, 3, 4, 7 and 9 assembled, form a portable public address equipment.
    Items 1, 2, 3, 4, 7, 8 and 10 assembled, form a public address equipment for classroom or assembly room use, using Tripod M-230-C for Loudspeaker LS-6-C and Microphone T-36-C. Either one or both microphones may be operated at the same time.
    1
    Par. 2
    Public Address Equipment PA-4-C
    TM 11-435
    CASE CS-9I-C
    | AMPLIFIER BC-64I-C
    LOUDSPEAKER LS-6-C	'* /•*, * vbl/	T
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    _J__.	________________________j
    Amplifier I3C-641-C
    	--------------------------1	।	-i a I .	J z-x , RED--------------- I	- I	tC0\ 1 WHITE------------------I
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    <	0	__________________________________-1	!________________________________________I
    Figure 8. Public Address Equipment PA-4-C, schematic diagram
    15
    16
    Section I. Supplementary Data 9. TABLE OF REPLACEABLE PARTS.
    NOTE: Order parts by Signal Corps Stock No., name and description. a. Amplifier BC-641-C. Stock No. 2C241C.
    Total	|	Contr’s
    Ref. Quantity Signal C.	Name of Part and Description	Mfr’s Dwg. or
    Symbol In Equip. Stock No.	Function	Code Part No.
    10	1	Case for amplifier BC-641-C	Housing for amplifier . A A1509
    11	1	Cover for amplifier case	Lid for 10	A	A1509
    12	#2	2C241C/S1 Screw, knurled top	Secure lid to case (10)	A 1508
    13	1	Dividing Plate	Separate amp. and batts.	A	A1508
    14	1	Chassis U frame	Amplifier chassis	A	A1508
    15	1	Pad, rubber	Insulates batteries	A
    16	#1	2C241C/C2 Compartment	Holds “A” batteries	A *ES-D-9223-A
    17	2	Side plate, laminated	( + ) Section of 16	A	*ES-D-9223-A
    18	1	Side plate, laminated	(—) Section of 16	A	*ES-D-9223-A
    19	2	Spring, contact, coiled	(—) Contact of 16	A	*ES-D-9223-A
    20	1	Retainer plate, nickel-silver	To hold 19	A	*ES-D-9223-A
    21	2	Stud, contact, nickel-silver	( + ) Contact for 17	A	*ES-D-9223-A
    22	1	Plate, bottom of compartment	Bottom of 16	A	*ES-D-9223-A
    23	#2	2C241C/C5	Connector, 2 contact, flat fiber	“B” battery connector	A
    24	#1	2Z9969	Transformer, 250 ohms to grid, input	Input stage of amp.	A	A7903
    25	#1	2Z9969-1	Transformer, driver, 2000 to 3500	ohms	Driver stage of amp.	A	A6236
    26	#1	2Z9969-2	Transformer, output, 10000 to 3	ohms CT Output stage of amp.	A	A6235
    27	#1	3Z6250-30 Resistor, fixed, 2500 ohms, r/z watt	Microphone coupling	C *SC-D-970
    composition
    28	1	Tube, Type 1H4G	Input tube	G
    29	1	Tube, Type 1J6G	Output tube	G
    30	#2	2Z8795-12	Socket, 8 prong, type MIP-8	For 28 and 29	B
    31	#1	2Z8799-33	Connector, 3 contact female	Connector for T-36-C	A
    32	#1	2Z8799-220	Connector, 4 contact female	Connector for LS-6-C	A
    33	1	Clamp, steel	Fasten to 10	A
    34	1	Clamp, steel	Fasten to 14	A
    35	#1	2C241C/G1	Grommet, hole	Insulator for 14	A
    36	#1	2Z7262-25M2	Resistor, variable, 25000 ohms	Microphone control	C
    Composition, LM type
    9.
    Total	s Contr’s
    Ref. Quantity Signal C.	Name of Part and Description	Mfr’s Dwg. or
    Symbol In Equip. Stock No.	Function	Code Part No.
    37	1	Cover, steel	To cover 36	A
    38	1	Base, steel	Bottom of 37	A
    39	1	Pin, steel	To connect 37 and 38	A
    40	1	Spring, steel coiled	For 39	A
    .41	#1	6Z4049	Gasket, rubber, %" diam.	Insulator for 37	A
    42	2	Gasket, rubber, 1 diam.	Insulator for 31 and 32	A
    43	2	Gasket, thiokol, %" diam.	Insulator for 12 lid screws	A
    b. Loudspeaker LS-6-C.	Stock No. 6C46C.
    50	1	Horn, steel	Projector	A	1506
    51	1	Baffle, steel	Mounting for 53	A	1504
    52	1	Cone, steel	Housing for 53	A	1504
    53	1	Speaker assembly unit	Loudspeaker unit	A
    54	1	Handle, bakelite	Attached to 50	A	A1505
    55	#1	6C46C/S4	Switch, trigger type, D.P.S.T.	To operate LS-6-C	D	80605
    56	1	Strap, steel	Attached to 54 and 55	A	/
    57	#6	ft.	3E2146	Cordage, 4 conductor, type	CO-146	Attached to 54	E	CO-146
    58	#1	2Z3096.1	Connector, 4 contact male	Attached to 57	A
    59	1	Clamp, steel	Attached to 54	A
    60	1	Plate, steel	Reenforce 54 mounting	A
    61	#1 6C4hC/Ml Transmitter, carbon, single button	Voice operation	F 9811-AS
    62	1	Screen, bakelite	Cover for 61	F	9188-AS
    63	1	Housing, steel	Housing for 61	A
    64	1	Cover, steel	Cover for 63	A
    65	#1	6C46C/P1	Pad, sponge rubber, 1%" diam.	Insulator for 61	A
    66	#1	6C46C/R1	Cushion, sponge rubber, 3%" diam.	Insulator for 61	A
    67	#1	6C46C/R2	Ring, sponge rubber, 3%" diam.	Insulator for 61	A
    68	#7	6C46C/G1	Grommet, %" hole	Attached to 63	A
    69	1	Lug, terminal	Contact to 61	A
    70	1	Protector, rubber	Attached to 50	A
    TABLE OF REPLACEABLE PARTS—Continued
    17
    18
    •&U. S. GOVERNMENT PRINTING OFFICE : 1945 —0-626227
    9.	TABLE OF REPLACEABLE PARTS—Continued
    c.	Microphone T-36-C. Stock No. 2B1636C. T otal	Contr’s
    Ref. Quantity Signal C.	Name of Part and Description	Mfr’s Dwg. or
    Symbol In Equip. Stock No.	Function	Code Part No.
    80	1	Handle, bakelite	Handle for T-36-C	F	1516
    81	1	Housing, bakelite	Housing for 87	F	1516
    82	1	Ring, brass	‘	Lock ring for 87	F 1517
    83	1	Lock nut, brass	To lock 80	F
    84	1	Spring, contact, copper	( + ) Contact to 87	F	1519
    85	1	Spring, contact, copper	(—) Contact to 87	F	1519
    86	#1	2B1636A/S2 Switch, thumb type, D.P.S.T.	Operate T-36-C	F SC-D-1055-M
    87	#1	2B1109E/3	Transmitter, carbon type, contact terminals	Voice operation	F	9818A
    88	#24 ft.	3E2145	Cordage, 3 conductor type CO-145	Attached to 80	E	CO-145
    89	#1	2Z3096	Connector, 3 contact male	Attached to 88	A
    90	1	Screen, bakelite	Cover for 87	F	9188-AS
    d.	Shoulder Hamess ST-39. Stock No. 2Z8539.	SC-D-5685-B
    95	4	Buckle, brass	To adjust 39	H	*SC-D-5685-B
    ' 96	5	Snap, bronze	Attached to 39	H	*SC-D-5685-B
    97	4	End clip, brass	Attached to 39	H	*SC-D-5685-B
    e.	Tripod M-230-C. Stock No. 6C330B.
    98	1	Strap assembly, leather with fasteners	Attached to leg of M-230-C A ,1514
    attached f. Case CS-91-C. Stock No. 6C11C.	SC-D-7945-A
    #	Furnished by the contractor as part of maintenance parts groups.	* Indicates Signal Corps drawing.
    10.	MANUFACTURERS NAMES AND ADDRESSES.
    A.	Silman Manufacturing Corporation, Pittsburgh, Pa.
    B.	American Phenolic Corporation, Chicago, Ill.
    C.	Stackpole Carbon Company, St. Marys, Pa.
    D.	Arrow-Hart & Hageman Co., Hartford, Conn.
    E.	Diamond Wire & Cable Co., Chicago, Ill.
    F.	Connecticut Tel. & Elec. Co., Meriden, Conn.
    G.	RCA Manufacturing Co., Camden, N. J.
    H.	North and Judd Manufacturing Company, New Britain, Conn.
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