EICAS STATUS MESSAGES
None
PLACARD
As appropriate
 
REPAIR INTERVAL   NUMBER INSTALLED
ITEM
23-51-4 Push-To-Talk (PTT)
Switches    NUMBER REQUIRED FOR DISPATCH
    REMARKS OR EXCEPTIONS
1) Control Wheel PTT C 2 1 (M) One may be inoperative provided:
Switches    a) Associated Audio Selector Panel switch operates normally, and
b) Affected switch is deactivated.
2) Flightcrew Audio C 2 1 (M) One may be inoperative provided:
Selector Panel PTT Switches    a) Associated Control Wheel switch operates normally, and
b) Affected switch is verified failed open.

EICAS STATUS MESSAGES
None
PLACARD
As appropriate
MAINTENANCE (M)
Deactivate the inoperative control wheel PTT switch, as required, or verify that the inoperative Audio Selector Panel (ASP) PTT switch is open.
1. Deactivate Control Wheel PTT switch. Refer to Control Wheel Push-To-Talk Switch Removal/ Installation AMM 23-51-03.
A. For the Captain’s PTT switch, open and collar these circuit breakers on the overhead circuit breaker panel, P11:
1) INTERPHONE CAPT FLT AMPL DUAL PWR.
2) INTERPHONE CAPT FLT AMPL DUAL PWR.
B. For the First Officer’s PTT switch, open and collar these circuit breakers on the overhead circuit breaker panel, P11:
1) INTERPHONE F/O OBS DUAL PWR.
2) INTERPHONE F/O OBS DUAL PWR.
C. Remove the medallion and chart holder to gain access to the wire bundle.
D. Pull out the wire bundle to get access to the quick-disconnect terminals.
E. Use an extraction tool to disconnect either the microphone or the interphone switch, whichever is inoperative.
F. Cap and stow the affected wires.
 
  B757 - 200 MINIMUM EQUIPMENT LIST

G. Install the PTT switch, medallion and chart hold in the control wheel.
H. Remove collars and close circuit breakers previously opened.
I. Verify that the switch is deactivated by completing the appropriate operational test in Step 4 below.
2. Verify that the affected Audio Selector Panel PTT switch is open.
A. Provide electrical power (AMM 24-22-00/201).
B. Select BOOM on the audio selector panel and use the boom microphone for this test.
C. Press the PA select switch on the associated ASP, ensure that the PA MIC light is illuminated and that the receiver volume is properly adjusted.
D. Without pressing PTT on the ASP, speak into the boom microphone and determine if voice transmission can be heard over the Passenger Address system. If voice transmission can be heard, the switch is failed in the closed position and the audio selector panel must be replaced prior to dispatch. If no voice transmission can be heard, switch is in the open position.
　
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