Telecommunication line switching circuit

Details Telecommunication line switching circuit Telecommunication line switching circuit

1976-07-27

1977-12-13

Robinson, Thomas A.

Telegraphy

Systems

Printing

178 2R, 179 18FA, H04M 302, H04L 2502

Patent

active

040630455

ABSTRACT:
An isolated line switching circuit for direct connection of a telephone, teleprinter, or like telecommunication instrument to a transmission line, comprising a solid-state optical cell including a light-actuated optical receiver that generates an electrical current when illuminated by an associated light-emitting device (LED), and a switching transistor having its emitter-collector discharge path connected in series with the transmission line; the optical receiver is connected to the base and emitter of the transistor to drive the transistor conductive when the LED is energized by an actuation signal initiated in response to a ring signal. A high-resistance emitter-to-base circuit for the transistor drains the collector leakage current (I.sub.CBO) and maintains a high off resistance even at high temperatures.

REFERENCES:
patent: 3766325 (1973-10-01), Hatfield et al.
patent: 3894175 (1975-07-01), Zaffignani et al.
patent: 3941939 (1976-03-01), Holmes et al.
patent: 3952169 (1976-04-01), Vincent
patent: 4004106 (1977-01-01), Yachabach et al.

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