Sensor circuit for telephone line

Details Sensor circuit for telephone line Sensor circuit for telephone line

1992-06-12

1994-05-10

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379378, 379387, 379386, H04M 100

Patent

active

053115872

ABSTRACT:
A sensor circuit for telephone line includes a detection coil (52) inserted in a telephone line (22). The coil generates a magnetic flux according to a line current which flows in the telephone line. A magnetic sensor (54) such as a Hall element generates a voltage signal in response to the magnetic flux. An output of the magnetic sensor is applied to a comparing circuit (58) and a tone deriving circuit (60) via an amplifier (56). The comparing circuit includes two comparators one of which compares the voltage signal from the magnetic sensor with a first reference voltage (V1) and the other of which compares the output signal with 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 voltage signal of the magnetic sensor. The line current supervisory signal and the tone signal are applied from terminals (46, 48, 62) to a signal processing circuit (36) by which a facsimile or a telephone set is selectively enabled.

REFERENCES:
patent: 3920928 (1975-11-01), Lye
patent: 3920929 (1975-11-01), Tate
patent: 4366347 (1982-12-01), Takatsuki et al.
patent: 5065088 (1991-11-01), Habiro et al.

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