Telephone line monitoring circuit and method

Details Telephone line monitoring circuit and method Telephone line monitoring circuit and method

1978-02-24

1980-04-08

Robinson, Thomas A.

H04B 346

Patent

active

041974352

ABSTRACT:
A novel circuit and method are described for monitoring a telephone line of a switched telephone system. The line monitoring circuit is interposed in the telephone system between the local subscriber-line from the central office and the on-premise continuation of that line at the subscriber's location. The line monitoring circuit has component circuitry for sensing both line-to-ground faults and extraneous AC voltages of a predetermined magnitude and frequency. Upon sensing a line-to-ground fault or an extraneous AC voltage of the predetermined magnitude and frequency, a control signal is transmitted to a relay control element which operates to disconnect the on-premise portion of the line from the portion of the line which extends from the subscriber's premise to the central office of the utility company. Visual indicators are also provided with the circuit. The indicators show whether a line-to-ground fault or an extraneous AC voltage fault has caused the relay to operate. The line monitoring circuit also provides a closed loop impedance path which may be used to test the impedance of the central-office line after the line monitoring circuit has operated to disconnect the central-office portion of the system from the on-premise portion.

REFERENCES:
patent: 3636280 (1972-01-01), Wetzel
patent: 3773986 (1973-11-01), Tremblay
patent: 3919487 (1975-11-01), Gabrielson
patent: 3941950 (1976-03-01), Dunwoodie et al.
patent: 3989908 (1976-11-01), Budrys et al.
patent: 4041253 (1977-08-01), Altenburger et al.
patent: 4041255 (1977-08-01), Cambridge et al.
patent: 4051333 (1977-09-01), Schomburg
patent: 4143250 (1979-03-01), Simokat

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