| 摘要 |
PURPOSE:To insert and remove an optional communication unit to and from a transmission line without the influence upon signal transmission and reduce the power consumption, by providing power sources in connection parts of communication units respectively and by connecting them in parallel to the transmission line. CONSTITUTION:Connection parts 3 and trasmitting and receiving parts 4 of communication units T1-Tn are connected by photo coupling elements. A light emitting element 41 of a photo coupling element 51 for transmission is driven by a transmission signal, and a light receiving element 42 of a photocoupling element 52 for receiving receives an optical signal from a light emitting element 32. The element 32 is connected to a power source V and is connected to a transmission line 1 also. An element 31 is connected to the power source V and the in put side of a switching element Q, and the element Q is connected to the line 1. In the transmitting and receiving operation, the element 31 is turned on and off in accordance with the quantity of light emission of the element 41, and the element Q is turned on and off. Thus, elements 32 of other units emit the light, and signals from other units are received. |
