| 摘要 |
PURPOSE:To attain data exchange between transmitting/receiving units having an identical address by providing a transmitting/receiving mode change-over means which makes a receiving means inoperative state while setting and invert the means into operating state while resetting to the transmitting/receiving units. CONSTITUTION:When operating switches SW1-SW4 are thrown in the transmitting/receiving unit, a strobe STB signal is inputted from an FIFO buffer 15 to a transmission/receiving control circuit 4 to fetch an input data to terminals I1-I4 of the circuit 4. The circuit 4 detects the absence of a transmission signal on a power line l and superimposes the input data on the power line l via a transmission circuit 3 and a coupling circuit 11. A latch circuit 5 is set, the circuit 4 is changed over from the receiving enable state into the receiving disable state by a Q output of the circuit 4 and the transmission of signal is finished in this case, then the circuit 5 is reset and the circuit 4 is restored to the original receiving mode. The circuit 4 outputs the read data from terminals O1-O4 by the own address at the receiving side, causing relays Ry1-Ry4 to be operated via a relay drive circuit 18 to drive a load.A return signal is transmitted from the circuit 4 to the transmission side at the same time. |
