Automatic ringback for direct current monitoring system

Details Automatic ringback for direct current monitoring system Automatic ringback for direct current monitoring system

1979-01-25

1981-08-04

Yusko, Donald J.

Communications: electrical

Condition responsive indicating system

With particular system function

340504, 340506, 340511, 340661, G08B 2300

Patent

active

042825172

ABSTRACT:
A ringback circuit in a security protection system, of the type which monitors a dc current, automatically reports to remote premises that the central station has, at an appropriate time, received an indication that the dc current has been changed to the normal current level for night operation. At the central station, a change in the current level from normal daytime to normal nighttime current is sensed, activating an oscillator. An electronic current limiter in the communications line responds to the oscillator through an isolation circuit, oscillating the current in the communications line, which activates a buzzer at the remote premises.

REFERENCES:
patent: 3124793 (1964-03-01), Foster
patent: 3233232 (1966-02-01), Brennon
patent: 3341816 (1967-09-01), Davis et al.
patent: 3562730 (1971-02-01), Hill et al.
patent: 3702468 (1972-11-01), Sasaki
patent: 3786501 (1974-01-01), Marnerakis
patent: 3797008 (1974-03-01), Yuasa
patent: 3823391 (1974-07-01), Worsley et al.
patent: 3854127 (1974-12-01), Damon
patent: 3886932 (1975-06-01), Suessmilch

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