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H20741 H20742
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VOICE RECORDER SYSTEM - MAINTENANCE PRACTICES
EFFECTIVITY
Airplanes with Fairchild Cockpit Voice Recorder
1. General
A.  This section contains the removal/installation procedure for the underwater locating device of the cockpit voice recorder.
B.  The underwater locating device is mounted in an external bracket on the cockpit voice recorder front panel. The unit has a self-contained battery. There are no external electrical connections.
2.  Remove Underwater Locating Device (ULD) (Fig. 201)
A.  Remove the four screws, with shakeproof washers, and the end coverplate.
B.  Slide ULD out from mounting cradle.
3.  Install Underwater Locating Device (ULD) (Fig. 201)
A.  When horizontal mounting is used, position beacon with switch end forward (to the left when facing recorder). If vertical mounting is used, the switch end should be down to reduce accumulation of grease and dirt on the switch insulator.
B.  Slide ULD into mounting cradle.
C.  Rotate ULD so that markings and battery replacement date label can be read.
D.  Assure that water switch on the end of the locator is clean. Wipe clean with freon.
E. Secure ULD in place with the end coverplate and four screws. The ULD will protrude 0.010 to 0.015 inch so that the end coverplate will prevent ULD vibration when the four screws are tightened. Tighten screws until the end coverplate makes contact with the cradle frame.
4.  Test Underwater Locating Device
A.  Equipment Required
(1)  DuKane model 42A12 ultrasonic test receiver (Fig. 202)
B.  Functional Test
(1)  
Position ultrasonic test receiver approximately three feet in front of ULD.

(2)  
On test receiver set input selector to INT position and activate by turning gain control to full up.

(3)  
Temporarily short water switch, center contact on one end of ULD, to case with jumper wire.

(4)  
With tuning control set between 35 and 40 kHz, an audible pulse should be heard at approximately one second intervals. If the pulse rate deviates greatly from one per second or the signal is weak, the ULD should be replaced.

NOTE:  The ultrasonic test receiver may be checked by jingling keys or coins in front of the microphone. A change in tone should be heard in the loudspeaker.
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Dukane Model 42A12 Ultrasonic Test Receiver  505 
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VOICE RECORDER SYSTEM -ADJUSTMENT/TEST
1. General
A.  The following tests will provide assurance that the voice recorder system is functioning properly and is ready for use. There are no system tests or adjustments.
2.  Operational Test - Voice Recorder System
A.  Prepare to Test
(1)  
Provide ground electrical power to airplane.

(2)  
Check that VOICE RECORDER and INTERPHONE circuit breakers on panel P6-2 are closed:

B.  Test Voice Recorder System Operation
(1)  
Plug headset into HEADSET jack on voice recorder control panel.

(2)  
Press TEST pushbutton on voice recorder control panel for at least 5 seconds. During this time, ascertain that a 600-Hz tone is present at intervals of approximately 0.8 seconds and observe that the meter needle indicates in the green area.

NOTE:  Fluctuation of the meter needle during test is normal; however, a brief dip out of the green area indicates a defective channel.

(3)  
Press ERASE pushbutton on voice recorder control panel for 2 to 3 seconds and release. Ascertain that 400-Hz tone is present for 5 to 10 seconds after pushbutton is released.

(4)  
Release parking brake, press ERASE pushbutton on voice recorder control panel and release. Ascertain that 400-Hz tone is not present after pushbutton is released.

WARNING:  BEFORE RELEASING PARKING BRAKE, VERIFY THAT WHEELS ARE CHOCKED AND CLEAR ALL PERSONNEL FROM WHEEL AREAS.

(5)  
Reset parking brake, press ERASE pushbutton for approximately 1/2 second, and ascertain that 400-Hz tone is not present after release of pushbutton.
　
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