Captain and First Officer Stations

The captain and the first officer station cards have an interface to these components:

· Control wheel PTT switch

· Remote mic switch

· Audio control panel

· Hand microphone

· Oxygen mask stowage panel

· Headset

· Headphone

· Flight interphone speaker.

The control wheel PTT switch connects in parallel with the ACP RADIO - INT (or R/T - I/C) switch. The remote mic switch is in parallel with the control wheel MIC switch.

When you select MIC on the control wheel switch, push the remote mic switch or select RADIO (or R/T) on the ACP, the ACP sends the R/T-PTT discrete signal to the REU.

When you select INT on the control wheel switch or INT (or I/C) on the ACP, the ACP multiplexes the interphone-PTT signal with other control signals and sends the control signal to the REU.

The PTT discrete signal from the hand mic goes directly to the REU.

The microphone audio can come from these sources:

· Hand microphone

· Oxygen mask microphone

· Headset boom microphone.

The oxygen mask stowage panel sends a door discrete, MASK MIC ON/OFF signal, to the audio control panel. An open discrete, mask mic off, is door closed and a ground discrete, mask mic on, is door open.

The REU sends audio to the headset, the headphone, and the flight compartment speaker at each station.

When you use the hand microphone or the boom microphone, the REU decreases the volume to the flight compartment speakers.

Observer Station

The observer station card has an interface to these components:

· Audio control panel

· Hand microphone

· Oxygen mask microphone

· Headphone.

When you select RADIO (or R/T) on the ACP, the ACP sends a R/T-PTT discrete signal to the REU.

When you select INT (or I/C) on the ACP, the ACP multiplexes the interphone-PTT signal with other control signals and sends the control signal to the REU.

The microphone audio can come from the hand microphone or the oxygen mask microphone.

When you use the hand microphone, the REU decreases the volume to the flight compartment speakers. The PTT discrete signal from the hand mic goes directly to the REU.

The REU sends audio to the headphone. Remote Electronics Unit

The REU controls the audio in the flight interphone system.

The REU gets control and PTT signals from the audio control panels (ACPs). The REU sends timing signals to the ACPs to control the data multiplexing.

Date: 2015-12-17; view: 908