PURPOSE: To prevent the breakdown of an IC circuit and to eliminate the influence of a noise by connecting a monitoring side and a CCTV camera through a capacitor by an AC coupling transfer system, and setting a signal of 1/2 of a crest value of its signal as a two-input signal of a differential amplifier on the side for receiving transferred data.

CONSTITUTION: Data is transferred by an AC coupling transfer system, and a capacitor 7c is provided between an IC circuit 7 and an IC circuit 8 so as to cut a DC component of a signal of its transfer data. As a result, even if a signal line 3 comes into contact with a GND line 4, and short-circuits, the IC circuit 7 for a data output is not broken down. Also, at the time of receiving the transfer data, an average level of a signal of its data is set about 1/2 of a crest value of its signal. Therefore, an average level of a peak value of the signal of the transfer data is obtained by a peak detecting circuit 8a. A signal obtained by executing the gain adjustment of its average level by an amplifying circuit 8b becomes a two-input signal of a differential amplifier 8c. Therefore, no noise is contained in a reproducing data waveform of its transfer data.