B. Control
_______
 (1)  To place the system in operation, perform the following:
 (a)  
Supply electrical power (Ref 24-22-00/201).

 (b)  
Make sure that SELCAL circuit breaker on overhead panel P11 is closed.

 (c)  
Make sure that the VHF and HF communications systems operate correctly.

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757
MAINTENANCE MANUAL

CHANNEL ONE
SELECTED1ST LETTERA
SELECTED 2 SEC 2ND LETTER
SET Q
B

HOLDING
B RST Q
TIME
ISOLATOR SELECTED3RD LETTER
VHF-L
C

SELECTED AUDIO SEL PNL
4TH LETTER
DC VOLTS
POWER UP TO
D

INITIATE A RESET DC VOLTS
VHF-RINTERNALSSAME ASAUDIO SEL PNL
VHF-L NC
HF-L
INTERNALS
SAME AS

AUDIO SEL PNL VHF-L
MASTER DIMAND TEST HF-RINTERNALSSAME AS ONE
AUDIO SEL PNL VHF-L SECOND DC VOLTS PULSE
SCHMITT
PILOTS CALL PANELQ
TRIGGER NC QQ DC VOLTS
SELCAL ONE
L VHF LHFRSECOND
Q
PULSE
SCHMITT

B BB B
TRIGGER CABIN CALL GND
FWD MIDAFT ALERT CALL
B BBA B
TWO TONE CHIMEISOLATOR
GENERATOR
AURAL WARN BELL/CHIMEMODULE
28V DC
DC LEFT
DC VOLTS
BUS SEC 2

DC VOLTS OUTPUTAND FILTER
SELCAL REGULATOR P11 16 DEMULTI-
COMPRESSOR
HI
ACTIVE LO
AUDIO OUTPLEXER
AMPLIFIER FILTERS LEFT-VHF COMM XCVR
DEMULTI-PLEXER
DEMULTI-PLEXER
DEMULTI-PLEXER
CHANNEL 2 AUDIO OUT
HI INTERNALSLO
SAME ASCHANNEL 1 RIGHT-VHF COMM XCVR
NC CHANNEL 3
INTERNALS
SAME AS
CHANNEL 1

HILO CHANNEL 4INTERNALS
AUDIO OUT
SAME ASCHANNEL 1
LEFT-HF COMM XCVRHI CHANNEL 5LO
AUDIO OUT
INTERNALSSAME AS RIGHT-HF COMM XCVR
CHANNEL 1 CODE SELECT
A 1ST LETTER
CODE SELECT
B 2ND LETTER
CODE SELECT
C 3RD LETTER
CODE SELECT
D 4TH LETTER
SELCAL DECODER
SHORTING
RECPT PLUG

SELCAL DECODER
SELCAL System SchematicFigure 2
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757 FAULT ISOLATION/MAINT MANUAL
SELCAL SYSTEM
COMPONENT  SHT 102 FIG.  QTY  ACCESS/AREA  REFERENCE 
CIRCUIT BREAKER - -- FLT COMPT, P11 
SELCAL, C539  1  11G3 
BELL CHIMEL AURAL WARNING, M1000 PANEL - (REF 23-42-00, FIG. 101) PILOTS CALL, M51 MODULE - (REF 31-51-00, FIG. 101) DECODER - SELCAL, M180  -- 1  119BL, MAIN EQUIP CTR, E4-3  23-21-01 
RECEPTACLE - SELCAL SHORTING, M974 SWITCH - (REF 23-42-00, FIG. 101)  -- 1  119BL, MAIN EQUIP CTR, E4-3  * 
L HF COMM, (S4)  -- 1 
L VHF COMM, (S1)  -- 1 
R HF COMM, (S5)  -- 1
R VHF COMM, M189 R HF COMM, M153 L HF COMM, M152 TRANSCEIVER - (REF 23-11-00, FIG. 101) R VHF COMM, (S2) L VHF COMM, M188 TRANSCEIVER - (REF 23-12-00, FIG. 101) -- 1 

* SEE THE WDM EQUIPMENT LIST
Selcal System - Component Index
Figure 101

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757 FAULT ISOLATION/MAINT MANUAL

VHF COMM VHF COMM HF COMM HF COMM
FLIGHT COMPARTMENT
SWITCH, SWITCH, SWITCH, SWITCH, (S1) (S2) (S4) (S5)

PILOTS' CALL PANEL, M51 (REF)

Selcal System - Component Location
Figure 102

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