On Tue, 18 Sep 2018 at 05:27, Denny Esterline wrote: > Hmmm... It's been near twenty years ago, but I've run RS-232 on copper > over two miles. Granted at a lower baud rate and with actual line drivers > that were operating near +-25v. > Info only: Long long long long ago (probably almost 40 years) I trialled RS232 at 200 (!) baud on copper. I now do not recall levels used but it was either 0/+5V or standard RS232 +/- 12V. Range seemed to be "as many miles as you wanted". This was using telephone cable pairs which were brought into a building from a large number of telephone exchanges scattered around the city. I could daisy chain several exchange links if desired. (Someone else had set the arrangement up for other purposes and I made use of it). It seemed that at 200 baud something akin to "wet string" would suffice. I don't know what effect this may have had on telephone "traffic" in the cables. I assume this was thought of at the time but maybe not. It was only done as a short trial. Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .