Thanks for the reply, but now I'm more confused than ever...
Are you saying the S634 isn't compatible at all with the W140 radio system? If you do a search on this topic in the archives, there are folks who have apparently done it...
I've read that the S634 is switchable between the two protocols used by Mercedes. No?
The BlitzSafe website clearly says that the adapter I already have is the required one for 94-98 Mercedes (other than M Class) with the Alpine S634.
What I need to know is what else I need to replace my S601 with a S634.
Anybody out there that has done this???
Thanks, KenP