Method and apparatus for creating and detecting alarm condition

Details Method and apparatus for creating and detecting alarm condition Method and apparatus for creating and detecting alarm condition

1975-05-27

1977-08-02

Swann, III, Glen R.

Communications: electrical

Systems

Call station

325308, 340216, 340310R, G08B 1322

Patent

active

040400450

ABSTRACT:
A method and apparatus for detecting theft of television sets from motels and similar establishments which provide unattended television sets and service as a convenience for customers. The invention uses existing trunk lines utilized in a master antenna television system (MATV) for transmitting television signals to the sets, and does not require installation of additional conductors. A source of low 60 Hertz voltage is applied to each of the trunk lines, and there is associated with each television set a resistor. When the connection of a set to a trunk line is disturbed, the disturbance is detected as a change in resistance and the level of 60 Hz current flowing through the trunk line is caused to change. This change in current is detected at a central location to create an alarm condition. An audible alarm is also created at the location of the television set which was disturbed.

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patent: 3135951 (1964-06-01), Byrne
patent: 3289194 (1966-11-01), King
patent: 3346798 (1967-10-01), Dinger
patent: 3407400 (1968-10-01), Lurie
patent: 3408643 (1968-10-01), Sliman
patent: 3439359 (1969-04-01), Sliman
patent: 3544984 (1970-12-01), Hanson
patent: 3618065 (1971-11-01), Trip et al.
patent: 3766540 (1973-10-01), Schopfer et al.
patent: 3784930 (1974-01-01), Vosteen et al.
patent: 3886538 (1975-05-01), Takeuchi
patent: 3974492 (1976-08-01), Girismen

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