Fss-9\(V\)This specification covers a receiver and a processor which combine to form a passive ultrasonic sensor, designed to detect the sounds of forced entry into a protected space.

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MIL-DTL-52869C

APPENDIX A

TEST METHOD 2 - Continued.

2.2

Bandpass characteristics.

a. With the band-reject filter bypassed (jumper between terminals 2 and

3 of TB3 in processor), set the processor sensitivity to midrange (position 3)

and the test signal frequency to 25.5 kHz. Adjust the ultrasonic generator

SPL to obtain 0.5 V rms at processor TP2 as measured with the ac voltmeter.

b. Vary the test signal frequency from 20 kHz to 30 kHz. The response

at TP2 shall not differ by more than 4 dB above to 8 dB below the average

in-band response.

c. Keeping the test signal level constant, as in step a., set the test

signal frequency to 10 kHz and then to 40 kHz. For both frequencies, the

response at TP2 shall be not less than 24 dB below the average in-band

response that existed in step b.

2.3

Sensitivity control range.

a. Repeat step 2.2a, but set processor sensitivity to position 5 and

adjust ultrasonic generator SPL to obtain 1 V rms at TP2.

b. Set processor sensitivity to minimum (position 1).

The signal level

at TP2 shall decrease by at least 24 dB.

2.4

Notch filter characteristics.

a. Set the processor sensitivity to position 3 and the test signal

frequency to 26.3 kHz. Adjust ultrasonic generator SPL to obtain 0.5 V rms at

TP2.

b. Connect the band-reject filter in the processor (remove jumper from

terminals 2 and 3 of TB3, and connect jumpers between terminals 1 and 2, and

terminals 3 and 4 of TB3).

c. Using a signal generator, apply a sync signal of 26.3 kHz at an

amplitude of 1 V rms to TB2-7 in the processor.

d. Keeping the test signal level constant, as in step a, set the test

signal frequency to 26.3 +1.315 kHz and then to 26.3 -1.315 kHz. For both

frequencies the response at TP2 shall not differ by more than �3 dB from that

measured at 26.3 kHz in step a.

e. Keeping the test signal level constant, set the test signal frequency

to 26.3 +0.263 and then to 26.3 -0.263 kHz. For both frequencies the response

at TP2 shall be at least 36 dB below that measured at 26.3 kHz in step a.