Page "Vehicle audio" Paragraph 21

The headunit itself is usually a multi-purpose device that houses multiple types of components in its housing.

The most common components are a radio receiver / tuner usually with AM and FM bands, and a small amplifier for driving an audio signal to speakers.

Other possible components include various media devices, such as ( in older vehicles ) a tape player ( either 8-track or cassette ), CD player, DVD player, HD Radio, Satellite Radio, USB flash memory, and even a portable hard disk drive typically used in notebook computing.

Many head units also feature a DSP component, and equalization component ( such as bass and treble controls ), or a control interface for another feature on the car ( such as a back-up / parking camera, navigation system, trip odometer, etc.

).