757 MAINTENANCE MANUAL
PILOTS' CALL PANEL AUDIO ACCESSORY
SEE A UNIT (E4-3)
P5 PANEL
P11 PANEL
FWD
119BL
FLIGHT COMPARTMENT  MAIN EQUIPMENT CENTER
FORWARD MID RIGHT FORWARD ATTENDANT'S AFT ATTENDANT'S
ATTENDANT'S HANDSET
AFT MID RIGHT ATTENDANT'S
HANDSET (DOOR 1 LEFT)
(DOOR 2 LEFT)  HANDSET
HANDSET (DOOR 3 RIGHT)
(DOOR 4 LEFT)
SEE B
SEE B
SEE B
SEE B
HANDSET LOCATIONS
SELCAL
L-VHF-R L-HF-R

FWD MID AFT FWD MID AFT b
b
b
b
PILOT RESET PA
PILOT P.A.ALERT
GND
CABIN CALL
PASSENGER
ADDRESS
P.A.
FWD MID AFT ALERT CALL
PUSH TO TALK
PUSH TO TALK
RESET ALERT ALERT b
PUSH
b
b
a
b
PILOTS' CALL PANEL PUSHBUTTON SOFT-TOUCH
A
KEYBOARD KEYBOARD
HANDSET
(EXAMPLE)

B
Cabin Interphone System Component Location
Figure 1

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MAINTENANCE MANUAL

 (2)  In operation, 4 of the handset buttons call specific stations (FWD, MID, AFT, PILOT). The P.A. button connects the handset to the passenger address speakers to make announcements. The RESET button permits the attendant to make more calls without the need to put the handset back on the hook after each call. The button operates the same as when the handset is put on the hook. The ALERT button connects the handset to all stations at the same time. The
 P.A. PUSH TO TALK switch momentarily connects the microphone to transmit voice during passenger announcements.
 C. Pilots' Call Panel
__________________
 (1)  
The pilots' call panel is on overhead panel P5. The cabin interphone system connects to the pilots' call panel through three blue lighted call switches which indicate an attendant call (FWD, MID, AFT), and one blue lighted call switch that indicates an alert call (ALERT).

 (2)  
The call switches (FWD, MID, AFT) are used to signal the related attendant station. The ALERT call switch is used to make an alert call.

 3. Operation (Fig. 2)
_________
 A. Functional Description
______________________
 (1)  
Cabin interphone calling from one station to another is done by single-digit dialing. Pressing a call switch on a handset activates the system by sending two tones to the audio accessory unit. The tones are processed in the accessory unit and a signal is provided to the called station to turn on the call light. A signal is also sent to the PA system to generate a hi/lo chime for attendant calls or to the aural warning system to generate a hi chime in the flight compartment for pilot calls.

 (2)  
The FWD, MID, AFT, and ALERT call switches on the pilots' call panel make it possible for the pilot to make and receive cabin interphone calls. The light in each call switch comes on when there is an incoming call and go off when the pilot pushes the switch. Power failures will automatically connect the microphones of the cabin interphone handsets to the PA system.

 (3)  
The controller in the audio accessory unit monitors busy stations, and prevents incoming calls when a called station is busy. The controller also activates the PA hi/lo chime output, and causes the lamp driver to turn on the attendant call light. Attendant to attendant calling can be accomplished except under the following conditions:

 (a)  
Any station that has a handset off hook cannot be called.

 (b)  
No station can call another station that has been called but not answered; however, the station that placed the call can repeat the call.

 (c)  
Only one call can be made from a handset without first performing a reset.

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757
MAINTENANCE MANUAL

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