Construction and Performace of a PCM Frame Synchronizer with Self-Varying Threshold

In the decommutation of PCM data, synchronization is accomplished by the detection of a coded word located at a known position in the message frame. It is the detection of the code word that is of interest here. This may be accomplished in a more efficient manner with a synchronizer using a self-varying threshold. This device is interesting in that no manual setting by the operator is necessary, and tedious calculation of the correct threshold setting is eliminated. Such a synchronizer has been built and is currently being tested. The object of the paper is two-fold. First, a description of the logic adopted to implement the synchronizer is given. This includes the solutions adopted to provide the window centered about the sync code position and the realization of the equivalent to a double threshold in a fixed-threshold synchronizer. Second, a description and summary of the results of tests, which provide a direct comparison of performance for fixed- and variable-threshold synchronizers and which verify the superiority of the latter, are given.