(g) 
 Electronics Rack

(h)  
Aft Cabin Ceiling

525 
Jul 15/70  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-41-0 Page 501 

NOTE:  The service interphone amplifier gain control on the front of the audio accessory unit may be adjusted to obtain a comfortable listening level for all stations except the attendants' stations. The attendants' interphone potentiometer may then be adjusted to provide a comfortable listening level for the attendants' handsets.
(2)  
Position the SERVICE INTERPHONE switch to OFF and repeat step C.(1). Only the following stations should be able to communicate between one another.

(a)  
Forward Attendant's Handset

(b)  
Aft Attendant's Handset

(3)  
Select service interphone on the captain's audio selector panel.

(4)  
Establish satisfactory communications between the forward attendant's station and the captain's station.

(5)  
Repeat steps C.(3) and C.(4) at the first officer's and observer's stations.

(6)  
If no longer required, remove electrical power from the airplane.

525 
23-41-0 Page 502  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Jul 15/70 

FLIGHT AND GROUND CREW CALL SYSTEM - DESCRIPTION AND OPERATION
1.  General
A.  The system enables call signaling between the flight compartment and cabin attendants, between the flight compartment and ground maintenance personnel, and between cabin attendants. The system is used to signal personnel to use the service interphone system to communicate with the person initiating the call.
B.  The system consists of pushbutton call signaling switches, call indicating lights, and audible call indicating devices. The location of components is shown on Fig. 1.
C.  The system obtains operating power from 28-volt dc bus No. 1 through a circuit breaker on panel P18-4 (Fig. 2).
2.  Call Horn
A.  The horn is an electromechanical device located in the nose wheel well on approximately the airplane centerline.
3.  Chimes
A.  The flight compartment high-tone chime is an electronic device located in the aural warning devices box (Ref 31-26-0). This box is installed on the forward end of the control stand.
B.  The attendants' hi-lo tone chime is an electronic device located in the PA amplifier
(Ref 23-31-0). The PA amplifier is installed on shelf 1 of the E2 equipment rack.

4.  Passenger Signs Panel
A.  The panel is located in the P5 pilots' overhead panel and contains two call signaling switches and a blue call indicating light.
5.  External Power Receptacle Panel
A.  The P19 panel is located near the external power receptacle and contains a call signaling switch and two interphone jacks.
542 
Feb 01/76  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-43-0 Page 1 

H20687
Flight and Ground Crew Call Systems Component Location  557 
23-43-0  Figure 1  May 01/76 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

5C6  Flight and Ground Crew System Circuit 
Jan 20/83  Figure 2  23-43-0 
Page 3 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

6.  Attendants’ Panels
A.  A panel is located at the forward and aft attendants' seated stations. Each panel contains two call signaling switches and a switch to reset the attendants' call circuits.
7.  Master Call Lights
A.  An attendants' call light is located on the forward and aft master call annunciator light module. The attendants' interphone call lights are pink.
8.  Operation (Fig. 2)
A.  The system is supplied power through circuit breaker PASS AND CREW CALL on panel P18-4. The system is turned on by closing the circuit breaker.
B.  The system is used to signal crewmembers in the flight or passenger compartments or ground maintenance personnel to use the service interphone system to communicate with the person initiating the call.
C.  When the GRD CALL switch on the forward overhead panel is pressed, 28-volt dc power is applied to the call horn causing it to sound. This gains the attention of personnel outside the airplane.
D.  When the PILOT CALL switch on the external power receptacle panel or the CAPTAIN CALL switch on an attendant's panel is pressed, 28 -volt dc power is applied to the hi-tone chime causing it to sound. This gains the attention of personnel in the flight compartment. When either switch is pressed, the blue call light on the passenger signs panel comes on to provide an additional call indication in the flight compartment.
　
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