If you're trying to connect from a Windows 7 machine to a door controller via Keri Doors 4.x, and the serial-to-USB converter that you have doesn't seem to be working, try a Tripp-Lite USA-19HS (get the drivers here). Some other Keri tips, while I'm thinking about it... the default username and password are both Keri (case-sensitive), so change them. The location to modify the associated COM port in Keri Doors is under Setup>System>Network Config>Port (COM 1-4). Then you can click the Controller Status tab>Status ... which will launch the communication tool, and should report back the "Ctlr Type" and show as "online" in green, if everything is working. .