power in and a remote display which shows channel info and unit control. If your head unit has aux audio input, run the HDZ300 to that, wire it up to the radio harness and tuck it away. When you want to listen to HD, switch the head unit to aux audio, and use the remote display to control. You might have to use a RCA to 3.5 stereo adapter if you head unit only has that kind of aux input. If you don't have an aux input, you're pretty much out of luck and will need to find an alternative to your existing head unit.