Ringing device for a private automatic branch exchange

Details Ringing device for a private automatic branch exchange Ringing device for a private automatic branch exchange

1980-02-26

1982-01-12

Brigance, Gerald L.

179 84R, H04M 1902

Patent

active

043107281

ABSTRACT:
A ringing device for a PABX comprising an alternating signal source and a direct current source connected to a supply line for supplying a ringing signal to subscriber lines. A centralized off-hook condition detection circuit is connected in series with the supply line and a switch, and in series with each subscriber's line is a local off-hook condition detection circuit and a bidirectional contact. At the time of any off-hook, the switch opens the alternating signal circuit, and the corresponding answering subscriber's line previously connected to the ringing signal supply line is connected to the switching network of the PABX before the switch recloses the circuit for supplying the ringing signal to the other called extensions.

REFERENCES:
patent: 3720793 (1973-03-01), Hofman
patent: 3752924 (1973-08-01), Freimanis
patent: 3767857 (1973-10-01), Colas et al.
patent: 3882282 (1975-05-01), Picandet
patent: 3917909 (1975-11-01), Macrander et al.
patent: 4113990 (1978-09-01), Nojiri et al.
patent: 4199664 (1980-04-01), Grange et al.
patent: 4221935 (1980-09-01), Barsellotti et al.

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