| 摘要 |
The loop disconnect pulse regenerator is used for transmitting dial pulses from a PBX extension through to the exchange line. The circuit comprises a rectifier bridge (G1-G4) and relay (AR) circuit which responds to incoming ringing current from the exchange. For outgoing calls the exchange loop, between the exchange line 'a' and 'b' wires, is formed by a coil (AD/I), two relay contacts (1i,4i) and a second coil (AD/II) across the line. Whilst the pulse train is being transmitted, two further relay contacts (2v,3v) short circuit the coils (AD/I,AD/II) and the pulsing relay makes and breaks a loop contact (1i). A further contact (4i) breaks the loop circuit through one coil (AD/II) whilst pulses are being transmitted so that no parallel inductive path exists. Opening the same contact (4i) also puts a capacitance (C) resistance (Wi) spark quench circuit across the pulsing relay contacts (1i). |
