Chain-type door latch and alarm

Details Chain-type door latch and alarm Chain-type door latch and alarm

1978-11-30

1980-11-11

Trafton, David L.

Communications: electrical

Condition responsive indicating system

Specific condition

200 6193, 340545, 340548, G08B 1306

Patent

active

042335957

ABSTRACT:
A door latch and alarm apparatus has a support mounted on the door and a support mounted on the doorjamb. A relatively inextensible and flexible element is anchored to the door support and has a free end provided with an end piece fittable in a latch on the doorjamb support. A pair of conductors, one of which may be the inextensible and flexible element, extend from the door support to the end piece where they are connected together via a resistor. At their other ends these conductors are connected to a resistance detector which operates an alarm whenever the resistance between the two conductors increases, as when the conductors are broken, and whenever it decreases, as when they are short-circuited.

REFERENCES:
patent: 2747177 (1956-05-01), Keller
patent: 3714644 (1973-01-01), Hellstrom
patent: 3754224 (1973-08-01), Roy et al.

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