Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1997-03-19
1998-07-07
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361115, 361119, H02H 326, H04M 1100
Patent
active
057778361
ABSTRACT:
A novel line-current protection circuit and method that is useable with a PCMCIA modem card is disclosed. The protection circuit is adapted to detect when an excessive voltage is present across the tip and the ring leads of a telephone subscriber loop by sensing the amount of line-current being supplied to line interface circuitry disposed on the PCMCIA modem card. The protection circuit includes a current sensing circuit portion that is placed in series with the tip lead and which detects when the line current exceeds a predetermined maximum amount. In the event the line current exceeds the maximum, the current sensing circuit asserts an excessive line current signal. A control and delay circuit causes the relay circuit to open the electrical connection between the modem and the telephone line only when the line current exceeds a predetermined maximum amount for a minimum amount of time. The protection circuit also includes a backup fuse, which will trip if the primary components of the protection circuit fail.
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Petersen Daniel Paul
Price Tim Urry
Gaffin Jeffrey A.
Jackson Stephen
U.S. Robotics Mobile Communications Corp.
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