(a)  
The 65-kHz bias generator signal is applied to the erase head to erase the tape. The 65 kHz also shifts the audio band upwards to improve the linearity of the record amplifiers. The 65 kHz is also mixed and removed in the monitor amplifier.

 (b)  
Under certain conditions, push the ERASE switch on the control panel will cause the entire tape to be erased. Bulk erasure requires that the ERASE switch be pushed a minimum of two seconds when the airplane is on the ground with the parking brake set. When the ERASE switch is released after being pushed in for two seconds, 115 VAC, 400 Hz is applied to the bulk erase coil for five seconds. During the five seconds while the erasure occurs, a modulated sound can be monitored at the HEADSET jacks.

 (4)  
AIRPLANES WITH LORAL/FAIRCHILD SOLID STATE VOICE RECORDER; Under certain conditions, push the ERASE switch on the control panel will cause the solid state memory to be erased. Bulk erasure requires that the ERASE switch be pushed a minimum of two seconds when the airplane is on the ground with the parking brake set. When the ERASE switch is released after being pushed in for two seconds, the header data is removed so the data can not be read from memory and a 400-Hz tone can be heard for 14 seconds through the HEADSET jacks.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.

VOICE RECORDER CONTROL VOICE RECORDER
Voice Recorder System Schematic
Figure 2 (Sheet 1)

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MAINTENANCE MANUAL

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 MODEL A100A  TAPE BASED  ú
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MAINTENANCE MANUAL

Voice Recorder System Schematic
Figure 2 (Sheet 2)

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 ú  02  Page 7
 ú  Jan 28/02 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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MAINTENANCE MANUAL

VOICE RECORDER CONTROL VOICE RECORDER
Voice Recorder System Schematic
Figure 2 (Sheet 3)

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 ú  01  Page 8
 ú  Jan 28/02 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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 B. TEST
____
 (1)  
AIRPLANES WITH LORAL/FAIRCHILD TAPE BASED VOICE RECORDER; The play head and monitor amplifier are used to monitor test signals recorded on all tracks of the tape. Audio outputs are monitored at the HEADSET jack on the control panel and the jack on the recorder front panel. A 600-Hz detector monitors the test signals on each track and sends a 30 VDC pulse to cause the monitor meter to deflect on the control panel.

 (a)  When the TEST switch on the control panel is pushed, a 600-Hz test tone is generated in the voice recorder unit. A ring counter sequentially switches the 600 Hz test tone for 0.8 seconds to each of the four record amplifiers. If the test is successful, the meter needle will deflect into the green band, and at the same time a modulated sound will be heard over the headphone from the HEADSET jack.

 (2)  
AIRPLANES WITH LORAL/FAIRCHILD SOLID STATES VOICE RECORDER; The test switch on the control panel when pushed produces a 600 Hz test tone. Audio outputs are monitored at the HEADSET jack on the control panel or the jack on the recorder front panel and by observing the meter on the control panel. The test tones will alternate between the 4 channels.
　
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