PURPOSE: To obtain a low-cost and high-performance system, by multi-plexing digitally signals other than a video signal collectively and by transmitting them in a base band or modulating digitally a carrier wave to transmit them as one channel of frequency multiple signals.

CONSTITUTION: The control device (CC) side and the camera head (CAM) side of a signal transmission device for multiplex transmission of TV camera signals are connected by a coaxial cable 29', and transmission power is supplied from 1' to 32'. Video signals of three primary colors from 35'∼37' of the CAM side are received through filters, etc. by 4'∼6' of the CCU side and are outputted. Simultaneously, the synchronizing signal, the sound signal, the control signal, etc. other than video signals are digitized collectively by FSK modulation and are transmitted as one channel of multiple signals. For example, the DIG.FSK coded signal from a terminal 2' is outputted to a terminal 33' as a demodulated signal, and thus, these signals are multiplexed as 7 waves with a margin between adjacent waves as the whole. As the result, the number of parts is reduced, and crosstalk is reduced, and a cheap and high-performance system is obtained.