Sensor circuit for a telephone line

Details Sensor circuit for a telephone line Sensor circuit for a telephone line

1995-06-28

1996-07-09

Hofsass, Jeffery

Telephonic communications

Supervisory or control line signaling

Signal reception at substation

379377, 379378, H04M 322

Patent

active

055352723

ABSTRACT:
A sensor circuit for telephone line (10) includes a detection coil (12a) inserted in a telephone line (14). The coil generates a magnetic flux according to a line current which flows in the telephone line. A magnetic sensor (12b) such as a Hall element generates a voltage signal in response to the magnetic flux. An output of the magnetic sensor is amplified by an amplifier (16). A calling signal detection circuit (18) which receives an output of the amplifier includes a capacitor (20) for cutting-off a direct current component included in the amplified output. An alternating current component is inputted to a (-) input of a hysteresis comparing circuit (22) which receives a reference voltage (Vref1) at a (+) input thereof. Therefore, the alternating current component is converted into a pulse signal which is then withdrawn at an output terminal (34) as a calling signal for ringing a bell of a telephone set. In addition, a line current supervisor circuit (36) is connected to the output of the amplifier so as to detect the line current by utilizing reference voltages (Vref2, Vref3).

REFERENCES:
patent: 4022980 (1977-05-01), Kitajewski et al.
patent: 4191859 (1980-03-01), Sabon
patent: 4570034 (1986-02-01), Serrano
patent: 4920561 (1990-04-01), Mitchell

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