Importance

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Abstract

A method and apparatus are disclosed for scrambling and descrambling an audio signal. An interference signal is generated and is intermittently, preferably pseudo-randomly, added to the program audio as a function of control information generated either by means of hardware alone or by means of software. The scrambled audio and the interference signal are preferably transmitted on two carriers, e.g., two standard subcarriers used in TV broadcasting, together with the control information. A decoder descrambles the audio by substracting the interference signal from the scrambled audio at the proper times as indicated by the control information. Preferably, the interference signal, comprising a series of noise bursts, is transmitted on the same carrier as the control information, time-multiplexed with the latter. Alternatively, the program audio itself, subjected to a time delay, is used as the interference signal, in which case the second carrier bears only the control information.

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First Claim