(2)  
Ensure all interphone and DUAL PWR SOURCE circuit breakers are closed.

(3)  
Position the SERVICE INTERPHONE switch to ON.

C.  Test Service Interphone System
(1)  Using a handset at the forward attendant's station, establish satisfactory communications with the following stations:
(a)  
Aft Attendant's Handset

(b)  
Panel P19 SERVICE Jack

(c)  
APU (Auxiliary Power Unit)

(d)  
Right Wheel Wel1

(e)  
Left Wheel Wel1

(f) 
 Right Wing Refueling Station

(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 - Unpublished Work - See title page for details.  23-41-0 Page 501 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.

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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.
　
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