Glass break detector having reduced susceptibility to false alar

Details Glass break detector having reduced susceptibility to false alar Glass break detector having reduced susceptibility to false alar

1995-02-01

1996-04-23

Mullen, Jr., Thomas J.

Communications: electrical

Condition responsive indicating system

Specific condition

340550, G08B 1300

Patent

active

055107672

ABSTRACT:
A glass break detector system (10) includes a low frequency (LF) detector (28) that is responsive to a pressure wave transducer (12) to detect the amplitude of a low frequency, generally sinusoidal acoustic wave signal resulting from a physical contact with a glass window. The LF detector includes a peak analyzer (42) that compares absolute values of sequential first and second amplitudes (P1, P2) of a low frequency signal derived from the low frequency acoustic wave signal to determine an appropriate alarm response. The LF detector enables the alarm if the absolute value of the first amplitude (P1) is greater than the absolute value of the second amplitude (P2) or if P1 or P2 amplitudes exceed saturation thresholds. The LF detector also includes a slope analyzer (40) that determines whether the low frequency signal exhibits atypical characteristics that generally indicate glass breakage. The detector system includes mid-frequency and high frequency signal processing circuits to further reduce susceptibility to false alarms.

REFERENCES:
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patent: 4991145 (1991-02-01), Goldstein et al.
patent: 5117220 (1992-05-01), Marino et al.
patent: 5192931 (1993-03-01), Smith et al.

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