Telephonic communications – Subscriber line or transmission line interface – Protective circuit
Patent
1993-03-26
1994-11-01
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Protective circuit
379398, 379399, 379400, 338308, 338309, H01C 112
Patent
active
053613007
ABSTRACT:
A balancing resistor and thermistor network for telephone circuits, and combination with an external relay, which reliably handles all three levels of adverse conditions, automatically resets under certain conditions, is physically small in size, and is strong. It is a flat ceramic substrate on both surfaces of which are screen-printed thick-film balancing resistor films. Also screen-printed on both surfaces are termination traces having portions so located that when the substrate substantially instantaneously fractures it reliably and substantially instantaneously breaks the circuits through the resistive films, the fracture occurring in response to a sudden high-voltage overload. Accordingly, there is no damage to, or melting or burning of, small wires in the telephone circuits at points near to or remote from the balancing resistor network. A thermistor film is screen-printed directly onto the substrate at a central region where there is no resistive film. The thermistor is connected to a relay and its associated circuitry on the telephone line card (circuit board), acting as a sensor to control the relay so that the latter resettably interrupts current flow through the entire circuit board and thus through the balancing resistor network.
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Disclosure of IRC (formerly TRW) discrete wirewound resistor (Sheet 1).
Specification sheet for IRC discrete wirewound resistor (Sheet 1a).
Disclosure of Ericsson resistor pair (Sheet 2).
Specification sheet for Ericsson resistor pair (Sheets 2a, two pages).
Disclosure of Caddock Model 1789-16 (Sheet 3).
Specification sheet for Caddock Model 1789-16 (Sheet 3a), (same as Sheet 7a).
Disclosure sheet for Caddock Model 1789-22 (Sheet 4).
Specification sheet for Caddock Model 1789-22 (Sheet 4a).
Disclosure for Caddock Model 1789-15 (Sheet 5).
Specification sheet for Caddock Model 1789-15 (Sheet 5a).
Disclosure for Raychem two-side resistor (Sheets 6, two pages).
Disclosure for Caddock Model 1789-16 (Sheet 7).
Specification sheet for Caddock Model 1789-16 (Sheet 7a), (same as Sheet 3a).
Disclosure for Caddock Model 1789-22-2 (Sheet 8).
Specification sheet for Caddock Model 1789-22-2 (Sheet 8a).
Disclosure for Caddock Model 1789-53 (Sheet 9).
Specification sheets for Caddock Model 1789-53 (Sheets 9a, two pages).
Disclosure for Raychem PTC switch (Sheet 10).
Specification sheet for Raychem PTC switch (Sheet 10a).
Disclosure for Caddock Model LC2021-100-10-1.25 (Sheet 11).
Specification sheets for Caddock Model LC2021-100-10-1.25 (Sheets 11a, two pages).
Disclosure of Philips Components thermistor resistor (Sheet 12).
Caddock Electronics, Inc.
Dwyer James L.
Gausewitz Richard L.
Shehata M. N.
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