PURPOSE: To make it possible to classify viewers by terminal device by disabling free image reception over a specific channels among several channels unless a specific down data signal is transmitted to terminal device.

CONSTITUTION: In the CATV system that transmits various television programs from one center 4 to television receivers 3 provided to respective terminal units 35 through wire 5, programs are sent out of modulating transmission part 25 over special channels. In a down data signal sent out of data transmitter 28 in the center 4, data which are allowed to receive image of special channels are included, and terminal device 35 having received the data turnes to one of special channel when the communication control circuit operates to select the specific channel with the channel switch, so that images will be received over the special channel. Then, data transmitter 28 polls respective terminal device 35 and collects and analyzes 30 answers of viewers by answer buttons and then provides display 10.