Thomas John Jackson
Security Companies and Guards in Salt Lake City, UT

4197435, Apr 8, 1980

Feb 24, 1978

5/880911

Amos R. Jackson - Salt Lake City UT
Thomas C. Jackson - Salt Lake City UT

H04B 346

1791753R

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.