(6)  
On Fairchild model A100A voice recorders, only the TEST Pushbutton on the voice recorder control panel is provided.

(7)  
The bulk erase module contains timing circuits, relays, and erase circuits which apply 115 volts, 400 Hz ac to the erase coil in the tape transport. The bulk erase circuits erase all audio on the recorder tape within 10 seconds after the ERASE switch on the control panel is released. The bulk erase circuits will function only when the airplane is on the ground and the parking brake is set because the control circuit must be completed through relay K4 in landing gear accessory unit module M338.

B.  Control
(1)  
The voice recorder system operates automatically whenever power is applied to the unswitched electronics bus.

(2)  
To erase all data recorded on the tape, proceed as follows:

NOTE:  The tape can be erased only with the airplane on the ground and the parking brake set.
(a)  
Press ERASE pushbutton on voice recorder control panel and hold for at least 2 seconds.

(b)  
Release ERASE pushbutton.

NOTE:  Operation of the erase circuits may be monitored by plugging a headset into the jack on the control panel. After the erase pushbutton is released, a 400-Hz tone will be heard for 5 to 10 seconds.
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VOICE RECORDER SYSTEM - TROUBLE SHOOTING
1. General
A.  The following trouble shooting procedures are based on performance of the system operational test and are presented in a tree-type format to aid in rapid fault isolation.
B.  When a test step does not check out, find the box containing the trouble symptom and perform the stated action. Continue to follow a single line by analyzing the results of each test step until the required corrective action is determined. Perform the specified corrective action, then repeat the step at which the failure was encountered and complete the test to check out the system.
C.  All trouble shooting procedures are based on the assumption that wiring is OK and that electrical power is available. If the corrective action in the procedure does not correct the problem, check wiring using the wiring diagram.
2.  Prepare for Trouble Shooting
A.  Provide ground electrical power to airplane.
B.  Ensure that voice recorder and flight interphone circuit breakers on P6 are closed.
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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)  
　
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