Telex Airman 850, Руководство по обслуживанию клиента

Страница: 20 / 34

20 en | Maintenance Airman 850
09-2021 | V07 | F.01U.264.819
Customer maintenance manual
Bosch Security Systems LLC
6 Maintenance
6.1 Microphone validation and adjustment
6.1.1 Microphone / amplifier sensitivity check
Headphone specifications are designed to comply with FAA TSO C57a, RCTA DO-214, and
DO-160D.
The headphone has two (2) operations:
–
Passive- power is turned off.
– Active - power is turned on.
All modes tested, unless noted otherwise.
To test the sensitivity of the microphone, do the following:
1.
Construct a test circuit. For more information, see illustration below.
2. Connect the test circuit to the microphone plug of the Device-Under-Test (DUT) headset.
For more information, see
Connector views / wiring diagrams, page 18.
i
Notice!
Verify correct polarity of connections
MIC +
MIC -
8 VDC
220
1/4W 5 %
+
470
1/2W 5 %
25 Vdc
V OUT
CONNECT TO
MICROPHONE
PLUG
25
Figure 6.1: Airman 850 headset boom microphone sensitivity check and adjustment test circuit
3. Calibrate a lab microphone, either self-contained (such as Larson Davis sound level
meter) or a separate measuring microphone with supporting equipment (such as Bruel
and Kjaer type 4192 with type 2669-B preamp).
4. Place the calibrated lab microphone 1/4 inch (6mm) in front of an artificial mouth (Bruel
and Kjaer type 4227, GRAS 44AB, etc.) or an equivalent speaker.
5. Connect a signal generator to the artificial mouth or the speaker.
6. Adjust for an output of 104dB SPL at 1 kHz @ 1/4 inch from the opening to the lab
microphone.
7. Remove the lab microphone.
8. Position the DUT headset microphone 1/4-inch (6mm) in front of the artificial mouth or
the speaker.
i
Notice!
The front acoustic port of the boom mic should be aligned with the center of the artificial
mouth or the speaker opening.
9. Measure the output of the headset microphone with a digital voltmeter.