A method and apparatus for synchronizing the secondary side to the primary side of a transformer circuit are presented. A preamble which consists primarily of data pulses and inverted power pulses is used initially to obtain the parameters for and to set up a phase locked loop. For example, an edge-triggered one-shot circuit can be used to generate a reference clock from the preamble until lock is detected. Once the phase lock loop locks onto the clock, normal communication between the primary and secondary commences. The phase lock loop, which is in the secondary, is kept in phase during normal communication using valid Manchester edges from the transmit signal.