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A real-time pitch/periodicity detector has been implemented on the Bell Laboratories Digital Signal Processing (DSP) integrated circuit. The design is based on a novel modification of the autocorrelation type pitch detector. The modification allows the computation and peak-picking of the autocorrelation function of an 8 kHz sampled input signal to be performed within the memory and real-time constraints of a single DSP. The algorithm is intended for applications in speech processing and coding where pitch or a measure of long-term periodicity of a signal is required. Specifically it has been applied in the design of a 9.6 kb/s speech coding system discussed in a companion paper. The pitch detector measures pitch over the normal range of most speakers. It does not compute a voiced/unvoiced decision.