What type of circuit controls the amount of voltage from a power supply?

A regulator (or voltage regulator) is a circuit designed to automatically maintain a constant, steady voltage level at its output, regardless of changes in the input voltage or load current. In a power supply, this ensures the sensitive electronics in your radio receive the exact voltage they require to operate safely and predictably. The other choices serve different roles in a circuit. An oscillator generates a continuous alternating radio frequency waveform, a filter removes unwanted frequencies (or smooths out DC ripple in a power supply), and a phase inverter flips the phase of an AC signal. Only the regulator actively controls and stabilizes the output voltage.