Automatic exclusion circuit

Details Automatic exclusion circuit Automatic exclusion circuit

1975-12-02

1977-10-11

Claffy, Kathleen H.

179 17B, 179 38, H04M 168

Patent

active

040537200

ABSTRACT:
A relay is included in a subset of a key telephone system to connect the subset to a line selected by the line button of the system when the relay is activated. A control circuit is coupled to the relay and a key system positive ground to control the operation of the relay. The "A" lead of the key telephone system is coupled to the control circuit to disable the control circuit and, hence, the relay when the positive ground is coupled into the subset on the "A" lead and to enable the operation of the control circuit and, hence, actuation of the relay when the positive ground is not coupled into the subset on the "A" lead.

REFERENCES:
patent: 3514544 (1970-05-01), Chambers, Jr.
patent: 3591725 (1971-07-01), Morse et al.
patent: 3725601 (1973-04-01), Jetzt et al.
patent: 3860763 (1975-01-01), Sudoh et al.
patent: 3941943 (1976-03-01), Matheny
patent: 3961144 (1976-06-01), Hirate
patent: 3967076 (1976-06-01), Balzer

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