Sensor circuit for voice/fax switch with cascaded amplifier circ

Details Sensor circuit for voice/fax switch with cascaded amplifier circ Sensor circuit for voice/fax switch with cascaded amplifier circ

1993-12-15

1995-12-26

Hofsass, Jeffery A.

Telephonic communications

Supervisory or control line signaling

Signalling integrity protection

379372, 379378, H04M 100

Patent

active

054794994

ABSTRACT:
A sensor circuit for telephone line includes a line current detecting circuit (52, 54) which generates a detection signal in response to a line current flowing in a telephone line (20, 22). The detection signal is applied to a first amplifier (56), and the detection signal as amplified is not only further amplified by a second amplifier (57) but also applied to a tone deriving circuit (60) and a CI detecting circuit (61) via a coupling capacitor (59). The detection signal as amplified twice is applied to a comparing circuit (58) which compares the detection signal from the second amplifier with a first reference voltage (V1) and a second reference voltage (V2), so that a line current supervisory signal is outputted from the comparing circuit. The tone deriving circuit includes a band-pass filter and derives a tone signal from the detection signal from the first amplifier. The CI detecting circuit detects a CI (calling tone) on the basis of the detection signal from the first amplifier.

REFERENCES:
patent: 3962534 (1976-06-01), Ogawa
patent: 4022980 (1977-05-01), Kitajewski et al.
patent: 4506113 (1985-03-01), Blomley
patent: 4924191 (1990-03-01), Erb et al.
patent: 5311587 (1994-05-01), Ohta et al.
patent: 5361039 (1994-11-01), Michel
"Practical Analysis of Amplifier Circuits Through Experimentation", Lorne MacDonald, 1981 pp. 260-262.

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