PURPOSE: To prevent illegal looking and listening by extinguishing code data of a contract device and contract channel necessary for looking and listening stored in an RAM by opening the back cover of a television set.

CONSTITUTION: Contracted selected channel data are stored in an RAM11. Identification circuits 7, 8 detect RF input signal, and an identification signal of selected channel from a video signal. A comparating and discriminating circuit 10 compares and discriminates the identification signals of circuits 7, 8 and memory data of the RAM11. A restoring circuit 12 sends out video signals of selected channel basing on the signal of the circuit 10. When the housing case of the RAM11 is opened, a power source circuit 13 extinguishes data stored in the RAM11. Accordingly, looking and listening of special programs by uncontracted device and looking and listening of channels other than contracted channel can be prevented.