Synchronization recovery in a communications system

Synchronization between a transmitter and a receiver is effected by encoding and transmitting a synchronization pulse as a series of m first waveforms followed by a series of n second waveforms. The first and second waveforms are of the same duration and are transmitted in phase with each other; and m and n are positive real numbers, with m greater than one. The second waveform is different from, and preferably negatively correlated with, the first. When the receiver detects a series of first waveforms in the received signal, it locally generates a series of (either first or second) waveforms and correlates the locally-generated signal with the received signal. A change in correlation is detected as the synchronization pulse.