An authentication/decryption unit authenticates and decrypts video signals received from a video signal output device. An open-condition detector detects the open condition of a cabinet. A memory stores therein one of a first flag indicating that an authentication operation of the authentication/decryption unit is enabled and a second flag indicating that an authentication operation of the authentication/decryption unit is disabled. A micro-controller controls whether the authentication operation of the authentication/decryption unit will be enabled or disabled according to the flag in the memory. When the open-condition detector detects that the cabinet is opened, the micro-controller writes the second flag into the memory.