PURPOSE: To avoid wiring from being concentrated onto a master set and to obtain a sharp video image by connecting monitor television cameras to two common wires via a constant current circuit whose output current changes by a video signal and providing a termination resistor changing an output current into a voltage at the end of the two common wires.

CONSTITUTION: Each of the monitor television cameras PQ1-PQ8 is connected to two common wires L1, L2 via a constant current circuit 3 whose output current changes by a video signal. Termination resistors R1, R2 changing an output current into a voltage are respectively provided to an end of the two common wires, and the cameras PQ1-PQ8 are connected in parallel with a master set MQ1. The camera PQ1 sends the video signal to the two common wires L1, L2 via a constant current circuit 3, and an output impedance when viewing the two common wires L1, L2 via the circuit 3 is several kohms, and it is much higher than a characteristic impedance of nearly 75ohms of the two common wires L1, L2. Thus, even when one of the cameras PQ1-PQ8 is connected to the two common wires L1, L2, a standing wave due to mis-matching is not generated.