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Test
Push and hold the TEST switch on the cockpit voice recorder
panel to start the voice recorder self test. Hold the switch for at
least 1/2 second. The cockpit voice recorder panel sends a test
signal to the processor in the voice recorder.
The processor starts a tone generator that sends an 800 Hz tone
to the A/D circuits. The tone goes to each of the four audio
inputs. The A/D circuits change the tone to digital test data.
The processor lets the CSMU keep the digital test data for each
channel. Next, the processor gets the digital test data from the
CSMU and mixes it. The D/A circuits change the mixed digital
test data to an audio signal. This mixed audio tone goes to the
headphone jack on the control panel. The processor also sends
a signal to turn on the status indicator.
When the processor gets test data it sends a signal to turn on
the status indicator. The status indicator comes on with no
faults.
During the test, the processor monitors test data for faults.
When the processor finds a fault, it stops the signal to the status
indicator and stops the audio tone.
The status indicator comes on momentarily with no faults. At the
same time you hear the 800 Hz tone at the headphone jack.
A BITE indicator on the voice recorder comes on with a faulty
voice recorder unit.
Erase
You erase the memory of the voice recorder unit with these
conditions:
* Airplane is on the ground
* Parking brake is set
* Push and hold the ERASE switch for one half second.
You push the ERASE switch to send an erase signal to the
processor on the voice recorder. The processor disables the A/
D and the D/A circuits. The circuits send an erase signal to the
CSMU. The CSMU erases all the audio data in the memory.
While in erase, you hear a 400 Hz tone at the headphone jacks.
You hear this tone for five seconds.
Clock Input
The captain clock data comes into the voice recorder on an
ARINC 429 bus. This puts the time data into memory. The clock
input gives a time relation between the voice recorder and the
flight data recorder.
VOICE RECORDER SYSTEM - FUNCTIONAL DESCRIPTION
EFFECTIVITY
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Underwater Locator Beacon Functions
The underwater locator beacon (ULB) sends a sound signal
when in the water. It uses a battery for power. The battery sends
power to the oscillator that operates at 37.5 Khz. The transducer
changes an electrical signal to a sound signal and transmits the
signal once per second.
VOICE RECORDER SYSTEM - FUNCTIONAL DESCRIPTION
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
23-71-00-009
VOICE RECORDER SYSTEM - FUNCTIONAL DESCRIPTION
VOICE RECORDER SYSTEM - FUNCTIONAL DESCRIPTION
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
23-71-00-009
General
The cockpit voice recorder system has an internal BITE circuit
that lets you monitor and do a test of system operation.
A TEST switch on the control panel lets you manually start the
system test.
BITE Operation
The recorder does an automatic test at power up. It also does
continuous monitoring while in normal operation. When a
failure happens, the BITE stores the failure in memory and turns
on the BITE indicator.
You use BITE to do a test of all the recorder circuitry. When you
push the control panel TEST switch, BITE makes a test tone.
The recorder stores this test tone on each channel. BITE then
monitors the stored tone to make sure it has the correct
frequency and amplitude.
Operational Test
When the voice recorder has power, you can start the test.
You hear a tone on the headphone jack and the green status
indicator comes on for a short time.
The voice recorder BITE indicator stays off.
These are the results if the test fails:
* Green status indicator stays off
* Voice recorder BITE indicator comes on
* No tone on the headphone jack.
System Test
The system test does not do a check of the audio circuits to the
voice recorder. To do a test of these circuits, you must make a
test recording.
Do these steps to do a test of the captain, first officer, and first
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