Abstract: A master clock oscillator produces a series of control pulses to drive a multiple frequency L.E.D. illuminator and an optically coaxial synchronous detection system in an AC based organic/inorganic, ripe/unripe sorter. Data is collected by subjecting free-falling articles to a repetitious sampling cycle and detecting the reflected pulses. Counters running at differential rates, store binary data relating to the size and ripe/unripe condition of the article. At the end of the sampling period, an accept/reject determination is made, based upon the binary data.