A good example of oscillation is PA systems that produces feedback when a microphone moves in front of an audio speaker. The system rings as the microphone receives it's own amplified signal and tries to again amplify the signal.

Oscillation in a cellular repeater system is when an external donor antenna receives it's own signal produced by an interior antenna, creating a an infinite loop. Most wireless Wilson amplifiers are equipped with auto or manual gain control, which decreases the output of the amplifier upon detection of oscillation. This keeps the amplifier running at the highest level possible without damaging itself.