Also called a "receiver," the head unit provides the main controls for the radios (any combination of AM, FM, SiriusXM, HD Radio) as well as a CD/DVD player, GPS navigation, Bluetooth cellphone ...

For instance, the Mercedes Audio 10 CD head unit, as produced by Alpine in the late 1990s, features the Philips TEA688OH signal processor IC. This chip handles volume, treble, and bass controls ...