(f)
Bus Protocol Line A (Ref. Fig. 018) Data is transmitted via the data bus in frames of constant length. The director signals the start of a frame with a unique SYNC-sequence. The director then continues with the transmission of Pulse Code Modulation (PCM) data of six audio channels.
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CIDS Data Bus Protocols
Figure 018
R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-73-00Page 58 1201-299, 1Config-1 May 01/05 1 1 1CES 1 After this the director addresses one DEU and transmits discrete data or a command. It then pauses and the previously addressed DEU can then transmit one data word, which terminates the frame. The timeslot for transmission of the DEU is called a 'window' and is long enough to cope with transients and propagation times. In case of collision, the protocol ensures correct synchronisation of the next frame. For discrete data transmission, the director addresses all DEUs in a sequence, one per frame. For audio transmission, all audio data is provided in each frame (six channels). A command in an initial sequence programs each DEU to receive up to two channels. This is dependent on the seat layout of the cabin. This may be altered with a new program of the director's zoning table contained in the CAM. All data words on the data bus have a length of twelve bits. The data transfer on the top data line contains data for these cabin system components:
-
the passenger lighted signs,
-
the reading lights,
-
the general cabin illumination,
-
the passenger address loudspeaker,
-
the call switch and call light.
(g) Bus Protocol Line B (Ref. Fig. 018) Data is transmitted via the data bus in frames of constant length. The director signals the start of a frame with a unique SYNC-sequence. Next, the director addresses one DEU and transmits discrete data or a command in this sequence:
-
the broadcast interphone channel,
-
the captain audio channel. Then come ten windows for audio transmission from the DEUs. The director allocates a DEU to a certain window with a respective command. Normally not all windows are used. In case of collision, the protocol ensures correct synchronisation of the next frame. At the end of a frame the DEU addressed at the beginning of the frame has the opportunity to transmit discrete information to the director. All data words on the data bus have a length of twelve bits. The data transfer on the middle data line contains data for these cabin system and components:
-
the passenger address,
-
the cabin and flight crew interphone,
-
the attendant indication panel,
-
the area call panel,
-
the evacuation signalling,
-
the lavatory smoke detection,
-
the aft attendant panel.
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(h) Audio Signal Handling These inputs are provided in the director for connection of audio signals from:
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the AMU (PA and interphone),
-
the flight compartment handset (PA) service interphone,
-
the pre-recorded announcement sources.
**ON A/C 051-099, 201-299,
-the PES tape reproducer.
**ON A/C 001-049, 051-099, 101-105, 151-199, 201-299,
Additionally, interphone audio arrives via the middle line data bus. There are also internally generated chimes, EVAC horn sound and telephone tones.
1_ Balanced PA Inputs
Each balanced PA input has a software programmable filter. It
is adjusted according to the zoning table in nine bass-range
steps and nine treble-range steps.
2_ Unbalanced PA Inputs
The Automatic Gain Control (AGC) circuits control the level of
each unbalanced microphone input and middle line inputs.
Furthermore, each microphone input is high pass filtered
according to the zoning table.
3_ Chime Generation
The director contains three independant programmable chime
generators. The zoning table data controls the sequences and
combinations of each chime. The table also specifies when
chimes are generated.
4_ Channeling
When the director has processed the audio inputs, (and
generated any sounds), it digitizes them and multiplies them
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