oscillator

As nouns the difference between oscillator and helitron

is that oscillator is a tuned electronic circuit used to generate a continuous output waveform while helitron is (physics) a tunable form of microwave oscillator.

As nouns the difference between oscillator and multivibrator

is that oscillator is a tuned electronic circuit used to generate a continuous output waveform while multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as oscillators, timers, and flip-flops.