| 摘要 |
A set-top box is configured to mount therein a security device which stores security information on a broadcasting entity, and extracts transmission information for receiving a broadcasting signal modulated from a control signal from a head end. In the set-top box, it is detected that the security device is not mounted into a receiver, the demodulation mode for the broadcasting signal and/or the frequency of the broadcasting signal is changed to retrieve the broadcasting channel on which the transmission information on the broadcasting signal is transmitted, and then, the broadcasting signal on the retrieved broadcasting channel is received. When it is detected that a demodulator is synchronized with the broadcasting signal, the transmission information on the broadcasting channel is extracted from the demodulated broadcasting signal, the broadcasting signal is received based on the extracted transmission information on the broadcasting signal.
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