Communications – electrical: acoustic wave systems and devices – Echo systems – Presence or movement only detection
Patent
1988-08-03
1989-12-26
Strecker, Gerard R.
Communications, electrical: acoustic wave systems and devices
Echo systems
Presence or movement only detection
200 6162, 307116, 307141, 340566, G08B 1322
Patent
active
048902659
ABSTRACT:
A detector and alarm is provided for monitoring air pressure variations in a monitored space, which variations correspond to an intrusion. An infra-sonic detector includes a microphone or the like and a low pass filter to retain only low frequency infra-sonic signals. The instantaneous infra-sonic signals are compared against a variable reference signal, which is a voltage lagging or delayed variant of the instantaneous signals. In this manner the detector is self adjusting for slow variations in the instantaneous signals but responds immediately to rapid variations to trigger an alarm.
REFERENCES:
patent: 4468763 (1984-08-01), Braunling et al.
patent: 4586031 (1986-04-01), Grinneiser
patent: 4800293 (1989-01-01), Miller
Mueller Robert W.
Rabbit Systems, Inc.
Strecker Gerard R.
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