-
the 3rd priority: attendant stations
-
the 4th priority: PRAM
-
the 5th priority: Video
-
the 6th priority: boarding music.
**ON A/C 201-299,
(b) Annunciation and Source Priority An indication is shown on all attendant indication panels whenever a PA broadcast is performed (e.g. PA IN USE). The sound sources are divided into these priorities:
-
the 1st priority: flight compartment station AMU
-
the 2nd priority: flight compartment station handset
-
the 3rd priority: FWD attendant station
-
the 4th priority: attendant stations
-
the 5th priority: PRAM
-
the 6th priority: Video
-
the 7th priority: boarding music.
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**ON A/C 001-049, 051-099, 101-105, 151-199, 201-299,
(c)
Volume Control When an engine is running, the PA volume is increased automatically by +6 dB. The PA volume is also increased by +4 dB in the event of cabin depressurization. PA loudspeakers are installed on the RH and the LH side of the cabin in the Passenger Information Units (PIUs). Separate audio amplifiers in the CIDS DEUs A drive each loudspeaker independently. The output level range of this amplifier is -20 dB up to +10 dB in 2 dB steps. The CIDS director software controls the output level. 0 dB represents an output level of 500 mW continuous power. The peak power is limited to 5 W. The level control is divided into two sections. Section one is the master audio level adjustment with a level range of 0 to -12 dB. This means that all audio amplifiers in DEU A will alter their respective output level over this range. Section two is the local audio level adjustment with a level range of +/-6 dB. This means that only the respective DEU A audio amplifier will alter its output level. Each loudspeaker is adapted to the respective ambient noise conditions. The passenger address level is also selectable via PTP (only on ground and landing gear compressed) for:
-three cabin segments,
-four attendant areas,
-
increased by oil pressure high,
-
increased by cabin pressure low.
The passenger address audio settings are stored in the CAM for
all installed layouts.
(d)
Frequency Control The PA system is equipped with several frequency control facilities: The input frequency controls are different:
-
for balanced audio inputs in the CIDS director (for example boarding music),
-
for unbalanced audio inputs in the director and DEU B (e.g. PA
announcements via cabin handset). Each input bus has its own filter which is independently programmable. The unbalanced PA inputs circuits are equipped with Automatic Gain Control (AGC) . Additionally the DEU A audio is equipped with a bass filter for special ambient noise equalization. The director frequency controls are the main frequency controls. The DEU A output filters are independently programmable for each output. The different frequency control
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ranges are shown in the DEU and the director component descriptions in this chapter (Ref. paragraph 6.).
(3) Operation of the PA System
(a)
Energization Energization of the PA System is as for 'CIDS Energization'.
(b)
PA Announcements from Flight Compartment Handset The handset is mounted at the flight compartment center pedestal and contains an integral PTT switch. Pressing the PTT switch to key the PA system. It overrides lower priority PA sources, and broadcasts the speech over all PA loudspeakers. Sidetone is heard over the handset earpiece. A PA IN USE indication at all attendant indication panels accompanies these announcements.
(c)
PA Announcements from other flight compartment audio equipment Any of these flight compartment audio equipment may be selected to make a PA announcement:
-
the boomset microphone,
-
the hand microphone (with internal PTT switch),
-
the oxygen mask integral microphone. Three audio selector panels are available on the left and right sides of the center pedestal, and on the flight compartment overhead panel respectively. They provide identical facilities. To select the PA system, the rectangular PA button is pressed. It lights up green and connects the microphone audio to the PA system. The integral PTT switch in the hand microphone is pressed to key the PA system. When the boomset or oxygen mask is used, pushing the combined PA volume control/PA sidetone switch, switches the sidetone audio to the boomset or headset earpieces. The switch illuminates yellow. The knob adjusts the sidetone volume. Pushing the respective PA green and yellow switches a second time, disconnects the flight compartment audio source and flight compartment earpieces respectively from the PA system. You can monitor the PA sidetone at any time when you only select the volume/sidetone switch. When the PA (green) selector switch is activated, PA ALL IN USE is displayed at all attendant indication panels. PA announcements from the selected flight compartment audio equipment are broadcast over all PA loudspeakers. They immediately override PA audio from any other source.
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