Degraded Audio System Operation
If the remote electronics unit or ACP malfunctions, the ACP cannot control the
remote electronics unit. Audio system operation can be switched to a degraded
mode by placing the ALT–NORM switch to ALT. In this mode, the ACP at that
station is inoperative and the crewmember can only communicate on one radio.
The ACP transmitter selectors are not functional. The transmitter selector for
the usable radio illuminates when a station is operating in the degraded mode.
The receiver switches are not functional, and only the usable radio is heard at a
preset volume, through the headset. The speaker and speaker switch are not
functional at that station. In addition, the flight interphone and service
interphone cannot be used. The control wheel PTT switch INT position and the
ACP PTT switch I/C position are not functional since the flight interphone is not
functional.
The mask and boom microphones can be used for transmission on the usable
radio. The MASK–BOOM switch works normally in the degraded mode. The
mask and boom microphones can be keyed with the control wheel PTT switch
MIC position or the ACP PTT switch R/T position. The hand microphone is not
usable in the degraded mode of operation.
Audio warnings for altitude alert, GPWS, and windshear are not heard on an
audio system operating in the degraded mode.
An audio system operating in the degraded mode cannot access the passenger
address system through the ACP. The crewmember can still use the service
interphone handset and PA microphone if they are installed on the control
stand.
If the remote electronics unit or ACP malfunctions, the ACP cannot control the
remote electronics unit. Audio system operation can be switched to a degraded
mode by placing the ALT–NORM switch to ALT. In this mode, the ACP at that
station is inoperative and the crewmember can only communicate on one radio.
The ACP transmitter selectors are not functional. The transmitter selector for
the usable radio illuminates when a station is operating in the degraded mode.
The receiver switches are not functional, and only the usable radio is heard at a
preset volume, through the headset. The speaker and speaker switch are not
functional at that station. In addition, the flight interphone and service
interphone cannot be used. The control wheel PTT switch INT position and the
ACP PTT switch I/C position are not functional since the flight interphone is not
functional.
The mask and boom microphones can be used for transmission on the usable
radio. The MASK–BOOM switch works normally in the degraded mode. The
mask and boom microphones can be keyed with the control wheel PTT switch
MIC position or the ACP PTT switch R/T position. The hand microphone is not
usable in the degraded mode of operation.
Audio warnings for altitude alert, GPWS, and windshear are not heard on an
audio system operating in the degraded mode.
An audio system operating in the degraded mode cannot access the passenger
address system through the ACP. The crewmember can still use the service
interphone handset and PA microphone if they are installed on the control
stand.
