(d) Interfacing and control of cabin equipment sub-sections:
1 General Cabin Illumination Control
_ This director addresses each of the four connected illumination units on command from:
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the FWD ATTND panel,
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the Programming and Test Panel (PTP),
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the response to certain discrete inputs. The DEU responds and switches each of the three outputs to the addressed ballast unit to open-circuit ('logic O') or to 28 V DC ('logic 1'). The table below shows the illumination level versus logic levels:
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2
_
3
_
4
_
CONNECTOR PIN 1, 4, 2,5, 3,6,
9,12, 10,13 11,14
OPERATION MODE S I G N A L
-------------- ---------------------------
bright 0 0 0
dim 1 (50 %) 1 0 0
dim 2 (10 %) 0 1 0
off 0 0 1
DEU or CIDS failure results in no 28 V DC outputs. This gives a 100 % illumination fail-state situation.
Flashing of Audio Control Panel and Lighted Sign Lamps The DEU responds to lamp ON or OFF control commands. It latches the respective outputs at 28 V DC or at open circuit. The director causes the flashing of any of these lamps by repeatedly transmitting ON commands followed by OFF commands.
Emergency Lighting Test (DEU B) When activated at the programming and test panel, Emergency Power Supply Units (EPSUs), connected to the DEU, are interrogated for their status. Fault situations in the EPSU are held in coded form. The code number corresponds to the fault type. A DEU B reads this failure number: The serial clock output pulses to the ON-state. The EPSU then replies and transmits an ON pulse to the DEUs 'Serial In' input, interpreted as a logic one. The process is repeated until there is a logic zero response from the EPSU. The number of received logic ones corresponds to the EPSU failure number.
Reading Lights (DEU A) All connections to the reading lights system are opto-coupled to maintain isolation of the DEUs DC ground from the reading lights AC ground. The director receives activation commands for lights via the PSS. It then signals to the respective DEU A to turn on the requested light. The DEU A then provides a connection between the respective reading light connection and the AC ground connection (from the reading light unit). The lights and lights Printed Circuit Boards (PCBs) are tested on command from the director. The R/L TEST output is activated. The DEU reads the logic level present on the R/L LAMP FAIL and R/L PCB FAIL inputs. It transmits the information to the director. This test is done via the programming and test panel.
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5_ Attendant Handsets (DEU B)
Up to two handsets may be connected in parallel to each DEU B.
The DEU performs hook-off sensing, and decodes the dial
information which arrives on the handset microphone line.
6_ Area Call Panels (ACP) (DEU B)
Two sets of ACP outputs are provided. Each set can drive up to
two ACPs in parallel.
7_ Attendant Indication Panels (AIP) (DEU B)
The director operates the AIPs via DEU B. A serial link from
the DEU B can be connected to two AIPs in parallel. Separate
service bus 28 V DC outputs and AIP BITE inputs are provided
for each AIP.
8_ EVAC Equipment (DEU B)
The DEU B has two essential 28 V DC outputs to drive EVAC
indicator lights. It also has three inputs for EVAC pushbutton
connection. The input detection circuitry is on the essential
bus and remains functional in an aircraft emergency.
9_ Additional Attendant Panel (DEU B)
The DEU B has a serial input, output and normal 28 V DC for
connection of an additional attendant panel.
(e)
Emergency Mode Activation In an aircraft emergency, the DEU operates in emergency mode. All impermanently used parts of the DEU switch off. The DEU A PA circuits and DEU B interphone and EVAC circuits remain energized.
(f)
Fail Safe States When a failure of the data bus interface, the director, or the data bus occurs the DEU maintains the current status of the discrete cabin systems outputs for approximately 3 minutes. After this delay the outputs switch into their pre-defined fail safe states. All audio input/outputs are immediately switched off.
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