E7H03 - Amateur Extra Class

E7H03 : What is a phase-locked loop?
A An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
B An electronic circuit also known as a monostable multivibrator
C An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
D An electronic circuit consisting of a precision push-pull amplifier with a differential phase input
Correct Answer: An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator