Door knob alarm device

Details Door knob alarm device Door knob alarm device

1979-05-03

1981-09-01

Swann, III, Glen R.

Communications: electrical

Condition responsive indicating system

Specific condition

307125, G08B 1322

Patent

active

042875137

ABSTRACT:
The alarm device includes a resilient metallic spring strap which is received over a doorknob and against the shank of the doorknob and which forms an input contact to the device. The device further includes an oscillator which outputs a signal through a coupling network having a capacitive branch to ground that includes a capacitive path extending through the strap to the doorknob. When a person touches the doorknob, a capacitive path to ground is established that causes increased attenuation of the signal level. A self-initializing and self-compensating amplifier in the device detects such drops in the signal level and triggers a pulsating alarm. The circuit needs no manual adjustment.

REFERENCES:
patent: 3200306 (1965-08-01), Atkins et al.
patent: 3697971 (1972-10-01), Domin et al.
patent: 4091371 (1978-05-01), Mason, Jr. et al.
patent: 4145748 (1979-03-01), Eichelberger et al.
patent: 4168495 (1979-09-01), Sweeney
patent: 4173755 (1979-11-01), Butler
patent: 4176348 (1979-11-01), Tobin et al.

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