Abstract: A method for reading or decoding the self clocking encoded data content of digital data bits encoded in the standard F2F or in phase shift format is described. The method is useful for decoding F2F or phase shift code signals presented in the form of optic, magnetic, or electric signal variations presented to a decoding apparatus for the extraction of data therefrom. The technique utilizes the measurement of the interval of time or distance elapsing between two like polarity signal transitions to determine the data content of that segment of the waveform bounded by the two similar polarity transitions. The data content of that portion of the waveform or signal stream is defined in accordance with a logical matrix of values corresponding to the F2F or phase shift code formats used.