| 摘要 |
PURPOSE:To make differ the supply voltage and the signal voltage given from the side of the master unit from the signal voltage level given from the side of the key telephone in case the wire signal transmission/reception is carried out between the master unit and the terminal unit such as the key telephone or the like. CONSTITUTION:When master unit C is connected to key telephone L1, the voltage of level VA is transmitted to power reception circuit 500 of the L1 side via l1 and power transmission circuit 700 in interface 5 of the C side to be used as the reference voltage for supply of the signals from the side of L1 of level VD. At the same time, the voltage of level VC is prepared for the signal supply from the C side. And these three levels are set to differ from one another. The clock signals sent from the C side based on VC and furthermore the data signals are transmitted to be received at signal reception circuit 540 and then to be switched to the communication based on level VD sent from the L1 side. Thus, line l1 is used in common by the time division. |
