Telephonic communications – Subscriber line or transmission line interface – Protective circuit
Reexamination Certificate
2005-04-26
2005-04-26
Mei, Xu (Department: 2644)
Telephonic communications
Subscriber line or transmission line interface
Protective circuit
C379S399010, C379S413000
Reexamination Certificate
active
06885745
ABSTRACT:
A protection arrangement for a telephone subscriber line interface circuit is disclosed. The arrangement is particularly useful for protecting an electronic telephone set from over-voltage and over-current fault conditions. The arrangement provides a FET that operates in saturation mode to connect an office battery to the subscriber line under normal operation. The FET also provides isolation capabilities for protecting the line circuit from an over-current condition on the subscriber line. Over-voltage protection is provided by way of an isolation relay between the line circuit and the subscriber line. Both the FET and isolation relay are operated by a controller that uses timers in the methods of over-voltage and over-current protection that it performs. A further capability of the arrangement is that it resets itself after the fault condition has ended. This feature is particularly useful in the case of fault conditions of short duration.
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Handforth Martin R.
Hupe Gerard J.
McGinn Donald S.
Meier Rolf G.
Planthara Canute
Briney, III Walter F.
Gorecki John C.
Mei Xu
Nortel Networks Ltd.
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