If you have a touch or iphone annd have ipod controls on your radio you might need this part
I have an Touch 2nd Gen and previously when I would connect it to my car I would get an error message: “Charging is not supported with this accessory” and would require me to manually bypass the message each time so that I could continue to use the iPod. That was the main problem since I would have to screw with the iPod every time I would start-up my car. Also, it would obviously disallow charging. This device fixed that problem! Now I can hook up my iPod and let it be. It always connects upon car start-up, and even gets the trickle charge from the 12V connection now.
Apple warned manufacturers for a few years now that they’re doing away with 12V “firewire charging” in favor of strictly using 5V “USB charging” in future devices. Unfortunately, not everyone got the memo I guess. This device is merely a 12V to 5V voltage converter, neatly packed into a small package with a male dock connector for plugging into your iPod and a female dock connector on the opposite end for plugging in your accessory. Simple and effective