You are right. Some HU's can work, but only with an adapter. The unit I bought has no way of accepting any type of controlling signal from anything but hte knobs and buttons on the unit. The the controls will not work. I knew this when I bought it. The most common way seemd to be to use the PAC adapter to generate IR remtoe signals forthose HU's that have a separate remote. Again, mine doesn't have this capability. No big loss, though.