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Abstract

A circuit for generating a timing signal in a Manchester decoder comprises an oscillator 10, a frequency divider 14 for dividing signals derived from the oscillator, and a comparator 18 for comparing the times of transitions in the output signal of the divider with transitions in input Manchester data. To form a digital phase locked loop, gates 12 and 16 are provided for selectively adding a pulse to and subtracting a pulse from the pulses applied to the divider 14 by the oscillator 10 in dependence upon the relative timing determined by the comparator 18, in such manner as to lock the phase of the output signal of the divider onto the phase of the Manchester data. A squelch circuit is also provided for inhibiting phase control by the comparator 18 in response to a drop in signal strength of the received signal containing the Manchester data.

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First Claim