Abstract: In combination with an asynchronous detector for detecting a particular digital word within a train of signals wherein the detector samples each bit in the train a plurality of times and provides a comparison signal in response to a predetermined number of correlations between the samples and a stored word, an analog to digital converter including signal conditioning means having first and second modes of operations for converting a received analog signal to a digital signal in both modes of operation and inserting periodic error pulses in the digital signal in the first mode of operation and switch means coupled to the signal conditioning means and the detector for switching the signal conditioning means between the first and second modes of operation in response to a comparison signal from the detector.