| 摘要 |
PURPOSE:To prevent the reduction in a carrier transmission signal level, by increasing the impedance of a terminal device at reception than that at transmission, in a system making multiplex transmission for a main controller and a plurality of terminal devices in time division. CONSTITUTION:A square wave logical signal 9 corresponding to a carrier return signal from terminal devices 2 and 3 is smoothed, and the impedance of the terminal devices 2 and 3 is made lower for the period of generation of the signal 9 in response to the smoothed signal and the impedance of the terminal devices 2 and 3 is kept lower for the period when no signal 9 is generated. Thus, the reduction of a voltage signal level of the carrier transmission signal from the main controller 1 is prevented. |
