cctalk Digest, Vol 70, Issue 3

Ethan Dicks wrote: Well, just to wade in with another 'opinion', if I have it correct: the transmitter must drive the lines within the range +/-5V to +/-15V, the receiver must respond correctly to signals in the range +/-3V to +/-25V. The hysteresis provides some noise immunity; the wider receiver specs allows for some line drop, noise, and common-mode bumping. There is also something like a 1K to 7K impedance spec on a receiver. -- If there were one thing about RS232 and (smart) modems that I wish had been differently, it would be that the hayes modem standard had permitted some technique to switch between data mode and control mode without having those 2 second guard periods. That was (is) so annoying waiting for dial-up software to get the modem into control mode. I haven't thought it through completely in relation to the RS-232 protocol reqs., but perhaps using the control sigs in some manner, such as dropping DTR and then sending some special character sequence; or using some otherwise-unlikely combination of control sig states.