| 摘要 |
electrical communications engineering; digital telephone sets. SUBSTANCE: device has power supply 4, first switch 8, two-wire channel buses 1, 2, input and output buses of four-wire channel, common bus, unit 3 having low dc and high ac resistance, voltage comparison device 6, second switch 9 that passes current in one direction, capacitors 5, 7, capacitor initial charging unit 10. Output of voltage comparison device 6 is connected to input conductor of four-wire channel; voltage across output of four-wire channel controls operation of first switch. EFFECT: improved reliability, reduced size. 16 cl, 4 dwg
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