Active digit cancelling parallel dialer

Details Active digit cancelling parallel dialer Active digit cancelling parallel dialer

1994-12-30

1998-01-06

Chiang, Jack K.

Telephonic communications

Supervisory or control line signaling

Substation originated

379130, 379200, 379283, 379355, H04M 150

Patent

active

057063419

ABSTRACT:
A method of dialing digits using dual tone multifrequency (DTMF) signals comprised of generating a digit from a DTMF generator comprised of a first pair of signals forming a DTMF signal, one signal of the first pair of signals being in a low frequency band and one signal of the first pair of signals being in a high frequency band, and applying the DTMF signal to a telephone line connected to a central office, detecting the first pair of signals in an auxiliary circuit and immediately applying a third signal in either of the low or high bands to the telephone line at the same time as the first pair of signals, and detecting the presence of the pair of signals and the third signal at the central office and preventing processing of the DTMF signal at the central office as a result thereof.

REFERENCES:
patent: 4776008 (1988-10-01), Ohkoshi
patent: 4939470 (1990-07-01), Kang
patent: 4998276 (1991-03-01), Hasegawa
patent: 5027389 (1991-06-01), Chiue et al.
patent: 5440622 (1995-08-01), Yuki
patent: 5535265 (1996-07-01), Suwandhaputra
patent: 5559874 (1996-09-01), Panosh
patent: 5590182 (1996-12-01), Stevens et al.

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