Pre-intrusion detection device

Details Pre-intrusion detection device Pre-intrusion detection device

1977-10-11

1979-09-18

Swann, III, Glen R.

Communications: electrical

Condition responsive indicating system

Specific condition

331 65, 340562, G08B 1322

Patent

active

041684958

ABSTRACT:
An intrusion detection unit comprises a compacitance having an "active" field, the coupling of which is significantly increased when an intruder comes into conductive relation with a doorknob. The unit is hung on the inside doorknob and is so arranged that the doorknob is the transmitting element of the capacitor, while a separate plate is the receiving element of the capacitor. The capacitor field is maintained actively charged by a battery driven oscillator which operates at a substantially uniform frequency and amplitude. The intrusion detector circuit is complete in itself and is not externally grounded by the intruder. The signal receiving portion of the circuit incorporates a square law amplifier, and also has means for adjusting the reference level to which the signal is compared.

REFERENCES:
patent: 2094351 (1937-09-01), Draper et al.
patent: 3440633 (1969-04-01), Vinding
patent: 3623063 (1971-11-01), Fontaine
patent: 3771152 (1973-11-01), Dettling et al.
patent: 3973208 (1976-08-01), Diamond

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