Reu Outputs

Each station card sends audio to these:

• Headphones

• Headsets

• Voice recorder

• Flight compartment speakers from CAPT and F/O station cards

• Communication transceivers

• Passenger address amplifier.

The station cards also send PTT signals to the communication transceivers and the passenger address amplifier.

AAU Signals

The AAU uses these audio signals:

• Altitude alert

• Ground proximity alert

• Flight interphone

• Service interphone.

The flight control computers (FCCs) send an altitude alert discrete to the AAU card. This input starts a C-chord generator.

The ground proximity computer and the weather radar receiver transmitter send alert audio to the AAU card. The AAU card combines this audio with the output from the altitude alert tone generator and sends it to each station card summing amplifier.

The summing amplifier combines the AAU alert audio with TCAS audio. Station cards amplify these signals and send them to these components:

• Voice recorder

• Headphones

• Headsets

• Speakers.

The flight interphone amplifier amplifies microphone audio from station cards. Microphone audio goes to the flight interphone jack.

The AAU card amplifies audio from the external flight interphone jack and sends it to station cards.

The service interphone amplifier amplifies these inputs:

• Audio from attendant handsets

• Audio from service interphone jacks

• Microphone audio when service interphone is set on the

ACP.

This audio goes to service interphone jacks and station cards.

Emergency Signals

Emergency operation bypasses all active circuitry in the system to maintain communications between the aircraft and ground stations.

Microphone audio and PTT signals from the CAPT and OBS stations go directly to the VHF 1 transceiver. Microphone audio and PTT signals from the F/O station goes to the VHF 2 transceiver.

Received audio from the VHF 1 transceiver goes to the CAPT and OBS station headsets. Received audio from the VHF 2 transceiver goes to the F/O station headset.