Audio Control Panels (ACP)
An ACP is installed at the Captain, First Officer, and Observer stations. Each panel controls
an independent crew station audio system and allows the crewmember to select the desired
radios, navigation aids, interphones, and PA
systems for monitoring and transmission.
Transmitter selectors on each ACP select one radio or system for transmission by that
crewmember. Any microphone at that crew station may then be keyed to transmit on the
selected system. Receiver switches select the systems to be monitored. Any combination of
systems may be selected. Receiver switches also control the volume for the headset and
speaker at the related crew stations. Audio from each ACP is monitored using a
headset/headphones or the related pilot’s speaker.
Audio warnings for altitude alert, ground proximity warning, collision avoidance, and
windshear are also heard through the speakers and headsets at preset volumes. They
cannot be controlled or turned off by the crew.
The MASK-BOOM switch allows selection of the oxygen mask microphone or the boom
microphone. The MASK–BOOM switch does not affect the operation of the hand
microphone.
Normal Audio System Operation
The Captain, First Officer, and Observer audio systems are located in a common remote
electronics unit in the E/E compartment. They function independently and have separate
circuit breakers. The audio systems are normally controlled by the related ACPs through
digital or computerized control circuits.
