Low-frequency alternating current signal detector, in particular

Details Low-frequency alternating current signal detector, in particular Low-frequency alternating current signal detector, in particular

1990-06-19

1993-06-08

Brown, Thomas W.

Telephonic communications

Supervisory or control line signaling

Signal receiver

379377, 379399, 379382, H04M 100

Patent

active

052186350

ABSTRACT:
A low-frequency alternating current signal detector for recognizing tone signals in a central office line interface circuit connecting a private telephone installation to an analog telephone network subscriber line. The low-frequency alternating current signal detector includes an amplifier (1) connected to the input of a bandpass filter (2) and to the input of a first rectifier-filter (3), a second rectifier-filter (4) and a threshold presence detector (5) connected to the output of the bandpass filter (2). The output of the threshold presence detector (5) selectively enables comparison by a comparator (6) of the bandpass filter input and output signals and signalling of the presence of an alternating current signal.

REFERENCES:
patent: 4386239 (1983-05-01), Chien
patent: 4540855 (1985-09-01), Szlam et al.
patent: 4599495 (1986-07-01), Richards
patent: 4689760 (1987-08-01), Lee et al.
patent: 4922528 (1990-05-01), Hubert et al.
IBM Technical Disclosure Bulletin, vol. 22, No. 9, Feb. 1980, pp. 4098-4099; Orengo: "Circuit for improving noise immunity in tone detection."
IBM Technical Disclosure Bulletin, vol. 26, No. 8, Jan. 1984; Y. Bonnet: "Tone detection circuit."

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