A television receiver includes a synchronous demodulator including a bi-phase stable PLL for controlling sampling of the received signal to produce data. A phase inverter reverses the phase of the data in response to a control signal. Data segment sync characters are recovered with a sync correlation...http://www.google.com/patents/US5621483?utm_source=gb-gplus-sharePatent US5621483 - Polarity selection circuit for bi-phase stable FPLL
