NAV-TV Head Unit and Zapco SX-SL II Signal Processor One of the biggest challenges with this car was the head unit. Mercedes Benz uses a fiber optic network for the entire system and tapping into the network was not an option. The Factory Command System was replaced with a unit from my good friends at NAV-TV. Nav-TV uses a European version of the Comand system. The Nav-TV unit has a factory TV Tuner built in in addition to the other modules. This unit has Cassette, Navigation, voice activated cell phone, CD change, AM-FM tuner, TV and 2 auxiliary audio-video inputs. All functions can be controlled from the steering wheel and allowed me to retain full usage of this amazing system.For video input, I utilized an Eclipse 3103 DVD player mounted in the glovebox, connected to a Zapco DA II sl digital to analog converter. Both regular CD and DVD's can be played on the eclipse unit and the DA converter can automatically sense which format is being played.Below the factory head unit is the world famous SX-SL II signal processor. The SX handles all of the crossover needs for the system and allows me to strike a perfect balance between the subwoofers and the front sound stage. It also allows me to turn the center channel on and off as needed.