Ringing control circuit in a telephone switching system

Details Ringing control circuit in a telephone switching system Ringing control circuit in a telephone switching system

1981-05-20

1983-10-11

Brown, Thomas W.

H04M 306

Patent

active

044094388

ABSTRACT:
In a ringing control circuit having a plurality of subscriber line circuits (LC.sub.0 through LC.sub.3) and a single ring trip circuit A (or a ringing loop-current detector) which operates commonly to all the subscriber line circuits (LC.sub.0 through LC.sub.3), an AND circuit (44) is provided in each subscriber line circuit (LC.sub.0 through LC.sub.3) for stopping the ringing operation by the subscriber line circuit. The ringing operation is initiated by said subscriber line circuit (LC.sub.0 through LC.sub.3), and is stopped when the subscriber lifts a handset. The AND circuit (44) stops the ringing operation upon reception of an answer detection signal from the ring trip circuit A indicating the lifting operation of a handset together with the phased ringing signal for the related subscriber. Thus, even when one subscriber lifts a handset, the ringing signals of other subscribers are not stopped, in spite of a single common ring trip circuit A. Thus, a central control unit does not need to re-energize a ringing operation of those subscribers which do not answer, when said ring trip circuit A provides an answer detection signal (a).

REFERENCES:
patent: 3076059 (1963-01-01), Meacham et al.
patent: 3978292 (1976-08-01), Hill et al.
patent: 3978293 (1976-08-01), Feiner
patent: 4081613 (1978-03-01), Reines et al.
patent: 4145577 (1979-03-01), Kojima et al.
patent: 4310728 (1982-01-01), Dumont
patent: 4355206 (1982-10-01), Israel et al.

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