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Abstract

A method and apparatus are provided for reducing the amplitude of signals that often are inadvertently coupled to a telephone line from an isolation barrier system, or that cause undesirable interference within the circuitry of the isolation barrier system. Such signals have undesirable peaks in the frequency domain (spectral peaks) due to the existence of periodicities in the data signal that is transmitted across the isolation barrier. Such spectral peaks are reduced by this invention, which comprises randomizing or scrambling the data signal before it crosses the isolation barrier, and descrambling the data after it has crossed the isolation barrier. In one embodiment, the data signal is scrambled by combining it with a random bit stream (or a pseudo random bit stream), which effectively 'whitens' the resulting scrambled signal, thus removing spectral peaks that exist in the original data signal. After the scrambled signal passes across the isolation barrier, it is descrambled by reversing the original scrambling operation. In preferred embodiments, both the scrambling and the descrambling steps are performed by combining the incoming signal with synchronized pseudo-random bit patterns using 'exclusive-or' logical operations.

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First Claim