Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1977-02-01
1978-08-08
Moose, Jr., Harry E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
361 45, 361 60, H02H 328
Patent
active
041060709
ABSTRACT:
Telephone terminal equipments connected to the network through the device described herein are prevented from applying potentially human-hazardous voltages or currents to the network. The device includes a pair of bifilar relay coils, one in each connection to the central office. These operate an associated relay contact only when an unbalanced voltage or current condition occurs on the customer leads. A circuit path is thus completed to operate a second relay, which opens the connection between the customer terminal leads and the network leads; and establishes a path to ground through its own coils for the current from the unbalanced source. Means are included for assuring that the fraction of hazardous voltage appearing across the second relay remains essentially constant in the frequency range of 17 to 60 hertz. Only removal of the unbalanced current can release the relay and restore the network connection.
REFERENCES:
patent: 3725613 (1973-04-01), Allen et al.
Gordon Alan Mayer
Mazurek Edward Francis
Wright Arden Bernard
Bell Telephone Laboratories Incorporated
Graves Charles E.
Moose Jr. Harry E.
Newman Harry L.
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