Unpermitted use protecting method by character generating circuit of v.c.r.

The locking device includes a procedure of waiting for the lock- function call and displaying the inputted secret code by using the OSD function when the locking function is called. A procedure checks whether the system is in the locked state after the secret code input is completed. A procedure stores the inputted secret code and locks the system if the system is not in locked state. A procedure compares the inputted secret code with the stored secret code if the system is in locked state. A procedure displays error message by making use of the OSD function if the secret codes don't match each other. A procedure unlocks the system if the secret codes match each other.