| 摘要 |
PURPOSE:To transmit the communication line polarity reversing pulse excellent in the noise interupting characteristics, by providing the DC communication current control means and performing the polarity inversion of communication line while no DC communication current flows. CONSTITUTION:When the start pulse ST indicating the transmission of charging pulse is incoming, a counter CNT is reset, a flip flop FF is set, and clock pulse is counted when the counter CNT is in the state of operation. The output of the count CNT is input to address terminals A0-A13 of ROM for address designation. Further, the output X1 controls the operation of a communication line polarity relay P, and inversion and restoration of communication line are made with the contactes P1, P2 of the communication line polarity relay P. Since the inversion and restoration of this polarity is made at the section when the current value is zero, noise can not almost be produced. |
