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There are four priority 3B inputs and six priority 2B inputs. The priority 3B inputs can go to one or more PA areas. Each priority 2B input can go to only one PA area.
PTT and Keyline Inputs
The PTT and keyline inputs tell the PAC when an audio input is active. The PTTs and keylines go to a discrete input buffer. The discrete input buffer sends the data to the microprocessor.
The discrete output buffer sends PA keylines to the in-flight entertainment (IFE) system for PA area announcements.
Audio Outputs
The microprocessor gets the PTT and keyline data. The microprocessor sends selection data to the audio switching matrix. The audio switching matrix sends the audio on the applicable channel or channels. Each channel is for a PA area. An announcement for PA area 1 goes out on channel 1. Announcements for areas 2, 3, 4, 5, and 6 go out on their related channels. If an announcement goes to all PA areas, it goes out on all channels.
The microprocessor uses configuration database information from non-volatile memory (NVM) to determine PA area assignments.
The six channels of PA audio go to the IFE system for the entertainment audio. This permits the passengers to hear the announcement on their entertainment headphones.
All six channels go to an analog to digital (A/D) converter. The A/D converter digitizes the six channels of audio and sends it to the speaker drive modules (SDMs).
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PAS -PA/CI CONTROLLER FUNCTIONAL DESCRIPTION

Volume Control
The PAS automatically adjusts the volume in the cabin. The microprocessor in the PAC calculates the correct volume for different volume zones. It sends the volume data to the SDMs. The SDMs adjust the volume. The PAC uses these four types of data to calculate the volume:
*
Configuration database

*
Flight data

*
Ambient noise sensors

*
Manual adjustment.

The configuration database gives the volume reference level for in-flight operation. All adjustments to the volume are from the in-flight operation reference level.
The PAC makes automatic adjustments based on either flight data inputs or ambient noise sensor (ANS) inputs.
The PAC normally uses ANS inputs. The ANSs send noise level data though the SDMs to the PA/CI controller. The PAC uses the data to calculate any adjustment and sends the data to the applicable SDMs.
EFFECTIVITY BEJ ALL
If all ANSs fail in an ANS area defined by the configuration database, the PAC uses the flight data inputs. You can also disable the ANSs from the CACPs, CSCP or through the configuration database. The PAC decreases the PA volume when the airplane is on the ground. It increases the volume as flight data changes. This is the data it uses and their effect on volume:
*
On ground, engines off (-6dB)

*
On ground, engines on (-2dB)

*
In air (0dB)

*
Maximum operating speed: (+2dB)

*
Decompression: (+8dB).

The PA/CI controller gets the flight data on the left ARINC 629 systems bus from these:
*
Airplane information management system (AIMS)

*
ARINC signal gateway (ASG) card

*
Warning electronic system (WES).

The CACPs and CSCP permit flight attendants to make manual adjustments to the volume. The PAC does not permit manual adjustment to lower the volume below the reference level.
Chimes
The PAS makes chime sounds for:
*
Cabin interphone calls

*
Passenger to attendant calls

*
Lavatory to attendant calls

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PAS -PA/CI CONTROLLER FUNCTIONAL DESCRIPTION

* Passenger information signs.
The PAC controls the chimes. The PAC uses data from the configuration database in NVM for the type of chime. These are the types of chimes:
*
Hi

*
Lo

*
Hi/lo

*
Lo/hi.

It uses data from different systems and makes a decision when to make a chime. The PAC sends chime data to the SDMs. The SDMs make the chime sound and send it to the speakers.
When a cabin interphone call occurs, the CIC sends the data to the PAC. The PAC sends the data to the applicable SDM or SDMs.
When there is a passenger to attendant or lavatory to attendant call, the applicable zone management unit (ZMU) sends the data to the PA/CI controller on the intersystem bus.
When the FASTEN SEAT BELTS or NO SMOKING signs go on or off, the PAS makes a chime. The PAC uses data from the left ARINC 629 systems bus to monitor the signs. These are the systems that supply data related to the passenger information logic:
* Airplane information management system (AIMS)
*
Electrical load management system (ELMS)
　
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