Frame Synchronization in Time-Multiplexed PCM Telemetry With Variable Frame Length

New methods of parallel and serial synchronization for time-multiplexed signals are presented. In the parallel case, i.e., when the sync code is transmitted on a separate channel,
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synchronization codes are generated by concatenating (in the sense used in concatenated codes) a common pn-like sequence of short length with words from a self-synchronizable code. The frame synchronizer can lock on any of the
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codes, which is particularly useful when frames of different lengths have to be transmitted. In the serial case, that is when each frame starts with an identical sync code, false sync due to replicas of the code, randomly generated by the data, is completely eliminated by transferring the sync code to the quadrature channel, while the data are transmitted on the inphase channel.