1976-02-12
1978-03-14
Claffy, Kathleen H.
179 18FH, H04M 1536
Patent
active
040792056
ABSTRACT:
An automatic number identification device is used in a telephone system to enable a telephone central office to identify from which of two parties on a two party telephone service a call is originating and is coupled to a pair of telephone lines extended from the telephone central office to one of the parties being served by the two party telephone service. A loop current sensor is connected in series relation with one line of the pair of the telephone lines forming a subscriber loop and detects when a specified loop current is present on the one line. When the loop current sensor detects such a loop current, a control circuit, energized by power derived from the telephone lines and coupled to the loop current sensor by a photo coupler, couples a resistive ground to both of the lines in the given subscriber's loop. The control circuit has an on-time delay so that ringing signals on the subscriber's lines do not effect the operation of the control circuit and an off-time delay so that dialing pulses are not distorted.
REFERENCES:
patent: 3005052 (1961-10-01), Powers
patent: 3019297 (1962-01-01), Boswau
patent: 3046343 (1962-07-01), Cox
patent: 3087019 (1963-04-01), Faulkner
patent: 3278687 (1966-10-01), Everett
patent: 3410961 (1968-11-01), Slawa
patent: 3579254 (1971-05-01), Carmody et al.
patent: 3855420 (1974-12-01), Steidl
patent: 4001512 (1977-01-01), Proctor et al.
Brigance Gerald L.
Claffy Kathleen H.
Cook Electric Company
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