The DC Quadricorrelator: A Two-Mode Synchronization System (abstract)

Summary form only given. The DC Quadricorrelator is a new form of automatic-phase-control circuit -which, when applied to color synchronization, gives better performance and appears easier to manufacture than circuits previously used. It provides automatic color synchronization without need for a manually-operated frequency or phase control. The circuit combines good noise immunity with rapid pull-in. Its performance and relative simplicity indicate a possible net reduction in overall receiver cost. The circuit also provides reliable, noise-immune automatic switching of receiver circuits for monochrome or color operation. The principle of operation of the "Quadri" is the fact that it supplements the APC loop with an additional detector operating in quadrature with the phase detector of the APC loop. This added detector develops an auxiliary dc control voltage only when the system is in synchronism. The presence or absence of this do voltage distinguishes between the in-sync and not-in-sync modes of operation. This voltage acts as a control signal which- switches a circuit parameter so that the APC loop has the necessary properties for good pull-in when it is not in synchronism and the necessary properties for good dynamic stability when it is in synchronism.