Integrated circuitry for exchanging signals between telephone station and central office

摘要

The two talking wires of a line loop extending from a subscriber station to a central office, provided with respective blocking capacitors, are connected on the subscriber side of these blocking capacitors to respective signal detectors fed from a common battery and cross-coupled by a common compensating capacitor. The two signal detectors receive outgoing signals from the central-office equipment via a common photoelectric coupler and transmit incoming signals to that equipment by way of respective bistable threshold comparators and individal photoelectric couplers. The two signal detectors with their threshold comparators are constituted in integrated circuity by mutually complementary transistors and diodes together with associated resistors.