Car Stereo Head Unit
The head unit is your mobile audio/video headquarters
The centre piece of any car stereo is the head unit. This is the brains of your car audio system; it controls all other connected components. The head unit is also referred to as the deck, receiver or CD player. Each term is used to describe certain functions of the car stereo, but doesn't always apply to the multitude of purposes an automotive head unit can perform.
Car audio has grown to include so many features that the very term "car stereo" really sells the range of possibilities short. Today your car stereo's head unit can double as control center for an LCD display in the back seat used to entertain the kids by playing back a DVD. The head unit can access a powerful global positioning system to track your automobile's movement and give specific directions everywhere you travel. But the main purpose of the car stereo head unit is still providing music.
Exotic car audio systems can be created including subwoofers, external amplifiers for added power and a multitude of speakers throughout your vehicle. Still, the average car stereo head unit you'll find is simply a CD player with four channel amplifiers rated from 40-60Watts. Most also offer a host of switching capability with pre-ins and main-outs for expanding the head unit to control a variety of other devices. Advanced head units will have an LCD display that is DVD and CD compatible with full color image display. There are even LCD based head units that have memory for custom animated images you can load up to give your car stereo a unique personal touch.
Pre-ins are auxiliary inputs that allow you to hook up a DVD or MP3 player or other external device allowing the head unit to act as a pre-amp. Main-outs are the outputs on the car stereo head unit that allows you connect external amplifiers for added power or extra speakers. One important output is the subwoofer out. This is a "low level" or non-amplified output that will connect to a powered sub or an external amp that will control a passive subwoofer design.
The head unit is the control center of your car stereo. Most of today's car stereos even include a remote control allowing a backseat passenger to control a multi disc changer located in the trunk and adjust the volume of a subwoofer under their seat. Car audio has come a long way and is now more sophisticated than ever. It is easy to see why they're not just limited to car stereo anymore- today they're more like mobile entertainment systems.