D. Procedure
(1)
Supply electrical power (Ref 24-22-00/201).
(2)
Do a Test of the Installed PTT Switch:
(a)
At a pilot’s Audio Selector Panel (ASP), set the audio selection to the flight interphone system.
(b)
Push the Control Wheel PTT switch to the MIC position.
1) On airplanes with a Control Wheel detent PTT switch; make sure the switch stays in the detent position.
(c)
Make a voice announcement.
1) Make sure you hear the announcement.
(d)
On airplanes with a Control Wheel detent PTT switch; push the PTT switch again. Make sure the switch goes to the (center) off position.
(e)
Set the microphone selection on the ASP to the flight interphone microphone.
(f)
Push the Control Wheel PTT switch to the INT position.
(g)
Make a voice announcement.
1) Make sure you hear the announcement.
(h)
Release the PTT switch. 1) Make sure the switch goes to the (center) off position.
(i)
Put the ASP back to the usual condition.
(3)
Remove electrical power if it is not necessary (Ref 24-22-00/201).
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23-52-21 Page 404 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 01/98
AUDIO SELECTING SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ ALL EXCEPT B2509 and B2510 and
Airplanes with Digital Flight Interphone
1. General
A. The audio selecting system enables personnel in the control cabin to use the various airplane radio and communication facilities to perform normal flight communications and maintenance services. Audio selector panels may be used to complete VHF and HF (if installed) communications, communicate with personnel on the airplane with the interphone systems or make announcements to passengers with the PA system. Airplane VOR (VHF) navigation, marker beacon DME and ADF receivers may also be monitored.
B. Three audio selector panels are installed on the airplane. The captain's and first officer's audio selector panels are installed on the aft electronic section of the control stand. The observer's audio selector panel is installed on overhead panel P5. The flight interphone system microphones and headphones are connected through jacks to the audio selector panels. All audio selector panel functions are connected in parallel with the paralleling network on electronics rack shelf E2-1 (Fig. 1).
C. The dual power source for the audio selector panels is obtained from the 28-volt dc battery bus and unswitched electronics bus No. 2. The captain's and observer's audio selector panels power sources are from a single circuit breaker; and the first officer's audio selector panel power source is from a single circuit breaker. The two circuit breakers are on circuit breaker panel P6. The captain's and first officer's audio selector panels also complete power to the flight interphone system loudspeakers.
2. Switching
A. Each audio selector panel contains monitoring toggle switches, a rotary mike selector switch, a push-to-talk button, a boom mike/oxygen mask mike toggle switch, a volume control, an isolation amplifier, relays, diodes, filter, resistor circuitry, green indicating lights, and a rotary voice-both-range filter switch.
5C8
Jun 20/88 23-53-0 Page 1
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
H48738
Audio Selecting System Component Location 5B2
23-53-0 Figure 1 Sep 20/81
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5C8 Audio Selector Panel Switching
Jan 20/83 Figure 2 23-53-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Monitoring toggle switches connect audio signals from the various radio receivers and flight interphone system to the input of the isolation amplifier. Four monitoring toggle switches connect ADF and NAV audio to the rotary voice-range filter switch. ADF and NAV audio is either connected directly to the isolation amplifier input or filtered and then connected to the isolation amplifier input. The NAV-1 and NAV-2 toggle switches are provided with audio from VOR 1 and 2 systems respectively. DME audio is connected through the NAV-1 switch to the isolation amplifier. The marker beacon (MKR) toggle switch connects marker beacon audio directly to the isolation amplifier input. The OXY-BOOM toggle switch connects the oronasal mask mike or boom mike audio high to the audio selector panel relays. The PA toggle switch completes the muting control circuit for the flight interphone system loudspeakers whenever the switch is pushed up and the PA microphone (if installed) on the control stand is used.
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