Signal treatment circuit for burglar alarms

Details Signal treatment circuit for burglar alarms Signal treatment circuit for burglar alarms

1976-12-06

1978-08-08

Swann, III, Glen R.

Communications: electrical

Condition responsive indicating system

With particular system function

340558, G08B 1324

Patent

active

041060032

ABSTRACT:
In burglar alarms in which ultrasonic waves are transmitted into a protected space and reflected to a receiver which detects disturbances in the reflected waves caused by an intruder to actuate the alarm, the alarm might be actuated not only by an illegal intruder but also by a short pulse-type vibration. For such reason, the present invention is so designed not to be actuated by a short vibrations with a timer being inserted so as to be actuated only by an input signal continuing for more than a fixed time (practically 0.7 seconds). Further, when such signal continues for more than a fixed time and contains a sound of a telephone bell containing a high frequency component, the high frequency component controls a switching element, permitting a setting time of the timer to extend over a telephone ringing time, thus arranging the alarms not to operate.

REFERENCES:
patent: 3459961 (1969-08-01), Ravas
patent: 3838408 (1974-09-01), McMaster
patent: 3866198 (1975-02-01), Cohen
patent: 3962696 (1976-06-01), Smith et al.

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