The Nokia version is (if memory serves) a fairly standard 9600 baud serial link - open collector so that both Tx and Rx share the same pin. I think it's lower voltage than TTL (3v). The protocol is proprietary but there are smatterings of info on the web. E.g. http://www.panuworld.net/nuukiaworld/hardware/cables/basics.htm I doubt it would have any relevance to your Alpine stuff, but it might give you some ideas on what to look for in such a protocol. GB ----- Original Message ----- From: "Mark Perri" To: Sent: Tuesday, January 14, 2003 10:59 AM Subject: Re: [EE]: M-Bus protocol > The Nokia mbus protocol is a 1-wire system, but I couldn't find any details > on timing, etc. Though perhaps it's similar to the dallas 1-wire > sytem? At least it's a place to start. Anyway, thanks for the help. > > Mark -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.