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Abstract

A clock signal synchronization apparatus for decoding self-clocking encoded data generates data signals identical in frequency with the encoded data but progressively offset in time with respect to the encoded data signal. The delayed data signals are responsive to the clock rate of a clock signal generating means so as to be advanced or delayed in time with respect to the encoded data when the clock signal generating means is not synchronized with the encoded self-clocking data. The instantaneous binary states of the encoded data and the delayed data signals are sampled in parallel to detect one of a predetermined number of distinct trigger codes. The signals are continuously sampled to detect a correct following code after the detected trigger code to indicate that the clock signal is synchronized with the encoded, self-clocking data. Error codes will be detected prior to the correct following code for each distinct trigger code when the clock signal is delayed or advanced with respect to the encoded data. The amount of time that an error code is present is used to vary the clock rate of the clock signal generating means to bring it into synchronization with the encoded self-clocking data.

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First Claim