PURPOSE: To remove a control line and to make a transmission line of one line and to reduce the cost of wiring works by superposing a white balance control signal on a video signal to transmit it.
CONSTITUTION: A video signal is subjected to a DC component blocking capacitor 10, a transmission line 9, and a superposition circuit 7, and DC component in a DC blocking capacitor 11 is removed, then the video signal is inputted to a monitor 5. A white balance control signal outputted from a white balance remote adjuster 6 is a DC signal, goes to a superposed signal superposed on the DC component in the superposition circuit 7, and is transmitted to a camera head 12 through the line 9. A video signal component is removed from the transmitted superposed signal by a video signal polarity inverting circuit 4 and an adder 3, and thus a white balance control signal is reproduced. This control signal is inputted to a white balance adjustment circuit 2 in order to adjust the white balance of a camera.