| 摘要 |
Anti-theft circuit for a portable device, is disclosed, in which a correlation in a PN(Pseudo Random Number) sequence is employed for effective prevention of a portable device from being thieved, the anti-theft circuit including a transmission block disposed in the portable device having a block for generating a particular pseudo random number sequence and a multiplication block for always multiplying a "high' value to an output of the block for generating a particular pseudo random number sequence, the transmission block for converting an output of the multiplication block into an analog value and transmitting the analog value, and an anti-theft sensing circuit separate from the portable device for receiving a signal transmitted form the transmission block, sampling the signal, multiplying a sampled value to a pseudo random number sequence identical to a case of the transmission block, summing for a time period, comparing to a preset threshold value, and selectively providing an alarm signal to outside thereof according to a result of the comparison.
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