Telephone subscriber line battery feed resistor arrangements

Details Telephone subscriber line battery feed resistor arrangements Telephone subscriber line battery feed resistor arrangements

1983-10-03

1984-08-21

Envall, Jr., Roy N.

Electrical resistors

Resistance value responsive to a condition

Current and/or voltage

338 23, 338 25, 338308, 338319, 320 35, H01C 710, H02H 504

Patent

active

044673108

ABSTRACT:
Battery feed resistors are constituted by thick film resistors on a substrate, electrically in series with switching type positive temperature coefficient (PTC) resistors which are closely thermally coupled to the thick film resistors by being mounted on the substrate behind the thick film resistors or on insulating layers over the thick film resistors. Precise battery feed resistances and matching of pairs of battery feed resistors are achieved by trimming the thick film resistors. The PTC resistors prevent excessively high temperatures being reached in the event that external high voltages are applied to a telephone subscriber line to which the battery feed resistors are connected.

REFERENCES:
patent: 3914727 (1975-10-01), Sabricius
patent: 4255698 (1981-03-01), Simon
patent: 4413301 (1983-01-01), Middleman et al.
Doljak, "Polyswitch PTC Devices--A New, Low Resistance Conductive Polymer--Based PTC Device for Overcurrent Protection", Proceedings of 31st Electronic Components Conference, Atlanta, May 11-13, 1981, pp. 313-319.

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