Circuit for providing accurately spaced video and sound carriers

摘要

A circuit for producing two carrier frequencies (e.g. video and audio) spaced by an accurately controlled, predetermined frequency includes a common reference oscillator connected in two phase-locked loops. Each of the phase-locked loops includes a voltage-controlled oscillator adapted to produce an output signal at one of the carrier frequencies, and a phase detector for comparing a different predetermined fraction of the outputs of the voltage-controlled oscillators in each of the loops with a predetermined fraction of the output frequency of the reference oscillator.