CompuServe Messages

I've never seen a book about RS-422, I learned what I know about it from a 422 serial card's manual and little bits and pieces here and there. One thing I can tell you about it's differences from 232C is that 422 is only an electrical specification and performance requirements, no signal/connector assignments. RS-422 uses a twisted pair for the signals and senses a 5V _differential_ between the 2 conductors. Specified length is 4000 feet. RS-485 specifies the connections for multidropping up to 32 ports on one line, and is built upon 422's 5V twisted pair. Most 422 cards I've seen are also 485-capable, whether advertised as such or not. There's also an RS-four-ninety-something that adds the signal and connector specifications, if memory serves it uses something like a 39-pin D-shell with an optional D-shell for additional signals. Never did see a pinout on it though. The only reference given was the original IEEE documentation.