| 摘要 |
PURPOSE:To realize application to the control of a distribution line by varying a phase or frequency at a constant period, by preventing the lowering of a level due to crosstalk occurring during transmission from continuing for a long time, and by making it possible to transmit a control signal which enables invariably-definite control. CONSTITUTION:When signal (c) exists which is generated due to crosstalk from any other line, received signal (d) has the waveform equivalent to composite one between signals (b) and (c). The phase of signal (b) is switched at period (t1), and that of signal (c) is at period (t2), so that the time when the reception level is detection level Ls will not become longer than either (t1) or (t2). Therefore, the time when discrimination signal (e) of receiver circuit 21 is OFF becomes longer than either (t1) or (t2) a few times and control state signal (f), the output of holding circuit 22 with holding time T longer than either (t1) or (t2) is outputted, without discontinuity, for the period when control is required, so that definite control will be carried out invariably. |
