Telephone protection circuit

Details Telephone protection circuit Telephone protection circuit

1988-12-16

1989-07-18

Pellinen, A. D.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Load shunting by fault responsive means

361 57, 361 91, 361111, 361 93, 379412, H02H 904, H02H 902

Patent

active

048498467

ABSTRACT:
A circuit for protecting sensitive telephone equipment from voltage or current overloads on the TIP or RING line includes a resistor serially positioned in the line and a triac triggered by a voltage differential across the resistor. A pair of fast diodes is positioned on the line adjacent to the telephone equipment for momentarily clamping the voltage on the line at that point between ground and the voltage supply of the equipment. The mementary clamping of the voltage creates the voltage differential across the resistor which triggers the triac. The fast diodes are capable of passing current for a time sufficient to allow the triac to begin shunting current to ground. An enhanced form of the protection circuit includes a second pair of diodes extending in parallel with the fast pair of diodes and positioned on the line between the pair of fast diodes and the triac. Inclusion of the second pair of diodes allows the circuit to utilize a triac with a slower turn-on time and a higher on-state voltage.

REFERENCES:
patent: 3600634 (1971-08-01), Muench, Jr.
patent: 3790856 (1974-02-01), Hutchinson
patent: 3878434 (1975-04-01), Voorhoeve
patent: 4079211 (1978-03-01), Janssen
patent: 4099216 (1978-07-01), Weberg
patent: 4322767 (1982-03-01), El Hamamsy et al.
patent: 4377832 (1983-03-01), Toney et al.
patent: 4484244 (1984-11-01), Avery
patent: 4661878 (1987-04-01), Brown et al.
patent: 4713719 (1987-12-01), Kugelman
patent: 4758420 (1988-07-01), McCartney

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