(5) The front panel of the unit has a monitor jack, which accepts a standard phone plug. The purpose of the jack is to monitor the output of the tape channel number one. This is useful to do an operational test of the reproducer there in the main equipment center.
C. Main Multiplexer
(1)
The main multiplexer is installed on shelf 4 of the main equipment center rack E4 (E4-4).
(2)
The main multiplexer accepts 15 analog audio channels, and converts the analog audio to digital form. Then it multiplexes (combines) the digital data into a single data stream. The multiplexer also distributes the data stream to the four columns of SEBs.
(3)
The main multiplexer consists of an isolation amplifier for each audio input, analog-to-digital convertor circuits, multiplexing circuits and four line drivers (one for each column of SEBs). The main multiplexer also supplies fused 35v ac power to the SEBs. Circuit breakers for each column of SEBs are located on the front panel of the main multiplexer.
(4)
Stereo/mono switches are located on the main circuit board of the multiplexer. The switches are set to the proper position before the installation.
D. Seat Electronics Box (SEB)
(1)
A seat electronics box (SEB) is installed on the inboard seat of each seat group. The SEB is mounted to the seat frame by four pull-type plastic fasteners.
(2)
The SEB receives the data stream from the main multiplexer. The SEB demultiplexes the data and converts it from digital form back to its original analog form. The analog audio then goes to each PCU in the seat group.
(3)
The two D-type jacks on one end are the column connectors; they are interchangable. The telephone jacks on the other end connect to the PCUs. Cables connect the SEBs in each column of seats in series. The last SEB in a column has a termination plug installed on one of its column connector jacks.
E. Passenger Control Unit (PCU)
(1)
A passenger control unit (PCU) is installed in the armrest of each passenger seat. The PCU attaches to the armrest by a single screw on the front panel.
(2)
The PCU buttons provide channel selection and volume control. A two-digit, seven-segment display indicates the channel selected and is also used as a status indicator during the self-test. A jack for a passenger headset is provided.
(3)
A cable with a connector on the end is provided to connect the PCU to the seat harness running to the SEB. A jack on the rear of the PCU provides an output for an electrical-to-accoustic transducer, allowing a pneumatic headset jack to be mounted in the armrest adjacent to the PCU.
3. Operation
_________
A. Functional Description (Fig. 2)
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH PASSENGER ENTERTAINMENT ú
23-34-00
ú ú 04A Page 4 ú Jun 20/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
115V AC
MULTIPLEXER
R UTIL
POWER
SIDEWALL
ENT TAPE
+12VDISCONNECT
-12V
SUPPLY
6.3A
RPDR
VOLUMEHEAD
LH
TRANS-ASSY
SEB CCT BRKR
DUCER ELECTRICALHEADSETS P37
LED
ABC
TO NEXT
JACKS SEAT GROUP ORKEYLINE
M AFT LH CABIN SEATING TERMINATORTEST IND
MOTOR CONT HEAD AMP PASSENGER CONTROL UNIT (PCU) NO. 1
CH CH
23
(ONE IN EACH SEAT)
CH CH
14
BRD MUSIC
CHANNEL
SIDEWALL
DISCONNECTPCU NO. 2SELECT
6.3A
LH
OFF ON
MUSIC
PCU NO. 3
DE-MPX
LSI 1
SEAT ROW (TYP 3 SEAT ROW)DELTAMOD
AUDIO DET
STEREO
AND
/MONO
CHAN
TAG LSI 3 SWITCH
MICRO-MULTIPLEXING
PROCESSOR10 CHANNELS
TO NEXTAUDIO
SEAT GROUP ORFWD LH CABIN SEATING
TERMINATOR SIDEWALLDISCONNECTRH
PROCESSOR
VOLUME SEAT ELECTRONICS BOX (SEB)
MUSIC CONTROL (ONE AT EACH ROW)
TO NEXT 6.3A
SEAT GROUP ORFWD RH CABIN SEATINGTERMINATOR
LSI 4MULTIPLEXING10 CH + 4 CH +MANCHESTER CODE
SIDEWALL DISCONNECT RH
MOD
BOARDING MUSIC
LSI 2
REMOTE CONTROL
DELTA
TO NEXT MOD
SEAT GROUP OR7 CHAN
AFT RH CABIN SEATING TERMINATOR-5V +5VCH 1
KEYLINE SOUND
VTR POWER
SUPPLY CH 2
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