*
Electrical load management system (ELMS)

*
Overhead panel ARINC 629 system (OPAS)

*
Flap/slat electronics unit (FSEU)

*
Proximity sensor electronics unit (PSEU).

EFFECTIVITY
BEJ ALL

ARINC 628 Interface
PSS sends smoking area information and a no smoking signal to the IFE system on the ARINC 628 head-end interface.
The passenger interface for PSS is through an ARINC 628 zone interface to the IFE system. PSS gets attendant call requests and reading light inputs. PSS sends reset information and seat call status on the zone interface.
Intersystem Bus
Each of these components connects to the intersystem bus to control PSS functions:
*
CSMU

*
PA/CI controller

*
Zone management units (ZMUs).

The intersystem bus passes through the components it connects. A failure of any component cannot cause a failure of the bus.
Other Buses
The cabin control panel (CCP) sends command signals to the ZMU on a panel bus. The ZMU sends display data to the CCP.
The ZMUs get commands and data from the I/S bus to control data to the OEUs and IFE. Each ZMU has an EIA-485 bus to each column of overhead electronics units (OEUs).
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PSS -INTERFACES

Discretes
Each ZMU can control as many as 20 passenger master call lights. The ZMU also sends a token signal to each column of OEUs for software installation.
Each OEU has four voltage outputs and twelve signal returns. The OEU controls the signal returns for these passenger service items:
*
Passenger information signs

*
Return to seat and lock door signs in the lavatories

*
Reading lights

*
Row call lights.

Each OEU has four inputs to monitor signals from lavatory modules.
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777 AIRCRAFT MAINTENANCE MANUAL

PSS -INTERFACES

EFFECTIVITY BEJ ALL  23-33-00 
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PSS -OVERHEAD ELECTRONICS UNIT

General
The overhead electronics units (OEUs) control these components:
*
Reading lights

*
Call lights

*
Passenger information signs.

They also monitor signals from lavatories and waste tanks.
Physical Description
The OEU weighs 1.7 pounds. It has these dimensions:
*
Length -8.7 inches

*
Width -2.75 inches

*
Height -4 inches.

The OEU has three connectors. J1 is the voltage and data bus input/output. It receives data from the ZMU or another OEU and sends it to the next OEU through the same connector. For correct operation, install a jumper plug when you remove an OEU.
J2 provides voltage and signal outputs.
J3 provides voltage and signal outputs and gets discrete inputs.
Functional Description
The OEUs change 115v ac power to these voltages:
*
28v ac for lavatory and passenger information signs

*
12v ac for reading lamps

*
5v ac for row call lights.

The OEUs get signals from the ZMU to control these PSS related items:
*
Reading lights

*
Call lights

*
Passenger information signs.

The OEUs monitor lavatory-to-attendant calls and door latch discretes from the lavatory modules.
These systems and components also connect to OEUs:
*
Lavatory and crew rest smoke detectors

*
Water and waste system

*
Cabin lighting system.

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777 AIRCRAFT MAINTENANCE MANUAL

PSS -OVERHEAD ELECTRONICS UNIT

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D633W101-BEJ  Jan 05/2002 

PSS -OEU INSTALLATION -PASSENGER SERVICE UNITS

General
There are overhead electronics units (OEUs) in the center and outboard passenger service units (PSUs). There are also OEUs in other cabin locations. Three screws attach the OEU to a panel.
Center PSU
Release the PSU panel latches and lower the PSU to get to the OEU. The OEU is on a bracket approximately eight inches above the PSU panel.
Outboard PSU
The left and right OEUs are on outboard PSUs.
Release the panel latches and lower the PSU. The OEU is on the PSU panel.
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PSS -OEU INSTALLATION -PASSENGER SERVICE UNITS
　
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