| 摘要 |
PURPOSE:To make it possible to receive dial pulses accurately having no relation to distance by providing a method of inserting a DC component which has relation to a threshold level for discriminating the make and break of dial pulses. CONSTITUTION:A voltage obtained from resistance R1 detecting a line loop current is differentiated by CR differentiation circuit DIF. Capacitor C of differentiation circuit DIF is connected in parallel to resistance Rb so as to allow the DC component of a dial pulse to flow to resistance R1. Applying the output of this differentiation circuit DIF to voltage comparator circuit DET with a threshold level generates an accurate pulse waveform which has nearly the same make ratio as a pulse sent out from a subscriber's circuit and has no relation to the line resistance. |
