I understood that at least the nicer Central Point Option Boards (there were several different ones made) don't have any data decoder in hardware at all. The hardware simply records when transitions take place, and then pass this list to the software that does the decoding. (The Catweasel seems to work on the same principle, but it doesn't come with the decoding software...) -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927