4 Jun
2009
4 Jun
'09
10:32 a.m.
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.
I think that is correct.
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.
The point weas that the Smartmodem would work using only the TxD and RxD
data lines (it didn't use the control lines, simply because you couldn't
rely on them even existing on some RS232 interfaces) _and_ it could not
be fooled if the special sequence of characters to go to command mode
occured e.g. in a file download. It was assumed (I think quite
reasonably) that you'd not get the characters _and the pauses_ in a download.
-tony