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The patent describes a device for resolving ambiguity of the start of a split-phase coded data bit. The device is initially synchronized with the zero crossings or polarity transition points in the coded data. A first integrator integrates the signal over one-half the data bit interval, and holds this value. A second integrator integrates the signal over the successive portion of the data bit interval and these two integrator signals are then compared.

The patent relates to long strings of digital data which are preceded by a frame sync pattern or 'Barker' word. The Barker word is fixed and known to the receiver and the appearance of the Barker word enables the receiver to mark the beginning of a frame. The difficulty of detection of the sync pattern is compounded when the data has a bit error rate and when the sync word is transmitted amidst random data. Detecting the frame sync pattern is a problem of cross-correlation of the data stream with a stored replica of the Barker word sync pattern. This device is a detector for accurate frame sync detection using a minimum quantity of hardware and significantly simplifying frame sync pattern detectors.