Microphone Selector Switches

The flight interphone system gets audio from these microphones:

· Boom

· Oxygen mask

· Hand-held.

You push a transmitter selector to select a communication transmitter or system. You can select only one system at a time.

When you push a transmitter selector, this happens:

· The selector switch light comes on

· The received audio comes on at the volume set by the receiver volume control

· The microphone audio and PTT signals are enabled for that system.

When you push a PTT switch, the microphone audio and PTT signals go to the system set by the selector switches.

When the ACP initially gets power, the flight interphone system is active.

Receiver Switches

Push the receiver switch (push-on, push-off) to listen to communication or navigation system audio. Turn it to adjust the volume. You can monitor any combination of systems at any time.

CAUTION: DO NOT PULL THE RECEIVER SWITCH KNOBS.

THE RECEIVER SWITCHES ARE PUSH-ON/PUSHOFF TYPE. THE KNOB IS IN WHEN THE CONTROL IS ON, AND OUT WHEN OFF. IF YOU PULL THEM,

YOU MAY DAMAGE THEM.

Radio-Intercom PTT Switch

The radio-intercom PTT switch is a three-position switch with momentary contacts in the R/T and I/C positions. In the R/T position, the microphone audio and PTT signals go to the communication system set by the transmitter selectors. In the I/C position, the boom or mask microphone jacks connect to the flight interphone system. The radio-intercom PTT switch is in parallel with the PTT switch on the control wheel.

BOOM-MASK Switch

The BOOM-MASK switch allows selection of the boom microphone jack or the oxygen mask microphone as an audio source. The microphone audio goes to the communication

system selected by the transmitter selector and the PTT switches.

Filter Switch

The filter switch controls the filter that processes the navigation audio you receive. This switch has these positions:

· V (voice) position passes only voice frequencies through the filter and blocks the 1020 hz range frequency.

· B (both) position passes voice and range (coded station identification) frequencies through the filter to the audio output.

· R (range) position passes only range frequencies through the filter and blocks voice frequencies.

ALT-NORM Switch

You use the ALT-NORM switch to select either normal or emergency operation of the flight interphone system. Each station operates independently.

When you select NORM, the flight interphone system operates as usual.

When you select ALT, the flight interphone system operates in the emergency mode. The only ACP controls that operate are the BOOM-MASK switch and the R/T position of the PTT switch.

The hand-mic does not operate.

When you select ALT on the captain or observer ACP, you hear receiver audio from the VHF-1 transceiver at the headphone and headset jacks. When you key the MIC, the audio and PTT signals go to the VHF-1 transceiver.

When you select ALT on the first officer ACP, you hear receiver audio from the VHF-2 transceiver at the headphone and headset jacks.

When you key the MIC, the audio and PTT signals go to the VHF-2 transceiver.

Purpose

The remote electronics unit (REU) controls audio signals in the flight interphone system.

Date: 2015-12-17; view: 850