K90172
Passenger Address System Component Location 5C2
23-31-0 Figure 1 (Sheet 1) Oct 20/89
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5C2 Passenger Address System Component Location
Oct 20/89 Figure 1 (Sheet 2) 23-31-0
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
D. The amplifier uses silicon semiconductors to provide 30 watts of continuous audio power to an 83-ohm loudspeaker system. It accepts audio signals from microphones, tape reproducers, or other call/alert devices. It amplifies them for reproduction through a loudspeaker system and through headphones for sidetone.
E. The five inputs have individual level controls and solid-state priority switching. Photo switches are used in the input for dc voltage control of the audio inputs. Thus, key click is eliminated and isolation between control circuits and audio paths is provided. The pilot (flight compartment) announcements are the highest priority. The attendant announcements are the next highest priority. Prerecorded announcements (airplanes with prerecorded announcements) are the next highest priority. The lowest priority input is the boarding music. Boarding music is interrupted by prerecorded (airplanes with prerecorded announcements), attendant or pilot announcements. Pilot announcements override attendant announcements and interrupt prerecorded announcements (airplanes with prerecorded announcements) and boarding music. A compression amplifier, used with all microphone inputs, ensures an equal audio output level even though different levels are applied to the input.
F. The volume level of the audio system is changed to overcome the variations between ground and flight noise by an engines on/off control switch which is installed to operate automatically. Operation of this switch results in a reduced audio output when the engines are off.
G. The master gain control makes it possible to tailor the gain of the amplifier to a particular aircraft according to its size and acoustical characteristics. A 5-watt auxiliary amplifier in the amplifier minimizes acoustical feedback from the attendant's station and also allows desired chime tones to be sounded only in the attendant's speakers.
H. The high chime (587-Hz tone) and high/low chime (587-/494-Hz tones) will sound only when the passenger or pilot signals. The low (494-Hz tone) chime will sound when either the fasten-seat-belt or no-smoking sign is turned on or off.
I. The battery bus provides 28 volts dc to the amplifier through the PA AMPLIFIER circuit breaker on P6.
3. Loudspeakers
A. Eight-inch speakers are located in the ceiling panels in alternate passenger service units (PSU's). The forward and aft attendants each have a 5-inch speaker located in the center ceiling panel at the attendant's station. A 5-inch speaker is located in each lavatory.
4. Hand Microphones
A. Hand microphones are located on hooks at the attendant's panels and at the forward attendant's seat. The PTT button on the microphone must be pressed to transmit. Each microphone is equipped with a plug connector so it may be easily replaced or used at another station.
5C5
23-31-0 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Oct 20/89
5. Tape Reproducer
A. On GUN/XIA B-2501-B-2505, B-2511, B-2512, and B-2514-B-2516, music for the passenger address system is provided by a magnetic tape reproducer installed in the radio rack. The tape reproducer uses cassettes containing an endless loop of 4-track, 1/4-inch mylar tape providing a playing time of approximately 3 hours. Tape speed is 3-3/4 inches per second. Automatic track switching provides continuous playing.
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