PROBLEM TO BE SOLVED: To transmit a digital signal including literary works to a display device without deterioration through a digital transmission line and to prevent the digital signal from being illegally copied. ;SOLUTION: When a protection information detection means 111 detects copyright protection information, a 1st decode means 113 and a D/A converter means 114 convert a digital signal into an analog signal and an A/D converter means 115 and an encode means 116 convert the analog signal into a digital signal again. Thus, illegal copy of the digital signal requiring countermeasures for copyright protection is prevented while avoiding deterioration in the digital signal.;COPYRIGHT: (C)2000,JPO
展开▼