| 摘要 |
PURPOSE:To simplify the circuit constitution of a dial pulse sending circuit, by sensing dial pulses with a semiconductor switching element and shaping the waveforms of the dial pulses by utilizing a DC synchronizing circuit. CONSTITUTION:A bridge rectifier circuit 1 is used for rectifying the DC of a telephone circuit and is provided with a transistor 2 working as a switching element, relay contact 3 which sort-circuits the transistor 2, photo-coupler (PH1) 4 for controlling the transistor 2, DC synchronizing circuit 5, photo-coupler (PH2) 6 for accelerating the operation of the transistor of the DC synchronizing circuit 5, capacitor 7 for disconnecting DC, and transformer 8 for balance/ unbalance transformation. In such a way, by replacing a dial pulse generating circuit using a relay with the semiconductor switch 2 and alternating the dual waveform shaping which has been done by means of a separately provided relay by utilizing the DC synchronizing circuit 5 and controlling the impedance against AC, improvement in the reliability of the circuit and reduction in the cost can be realized simultaneously.
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