| 摘要 |
PURPOSE:To prevent piracy of a program with an incorrect means, by providing a means to detect if a specific signal from a center is normally received in a terminal device. CONSTITUTION:Between a branch device 30 and a tuning signal generating section 35, a series circuit consisting of a reception section 32 receiving an outgoing data signal, a clock detection section 33 and a timer 34 is provided. If a subscriber makes the outgoing data only at a terminal device not recieved with any means for the purpose of piracy, the reception section 32 can not receive the frequency in a specific signal, the absence of the clock is detected at the clock detection section 33 and transmitted t the timer 34. The timer 34 outputs an operation stop signal when the detection signal from the clock detection section 33 is consecutive, the tuning signal is compulsively changed to the preset channel to prevent piracy. |
