Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!aramis.rutgers.edu!athos.rutgers.edu!hedrick From: hedrick@athos.rutgers.edu (Charles Hedrick) Newsgroups: comp.sys.ibm.pc Subject: Re: Maximum Length of a PC Serial Cable? Message-ID: Date: 18 Jul 88 18:15:50 GMT References: <1986@silver.bacs.indiana.edu> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 18 If by serial you mean RS232 async, there are official limits on distance. They depend upon speed. I.e. you can get farther at slower speeds. At 9600 I think the official limit is something like 50 feet. It goes up to several hundred feet at 300. But these limits are incredibly conservative. (That's why I'm not taking the trouble to look up the actual numbers.) Lots of people use 9600 on cables that are several hundred feet long. We do at Rutgers. There is generally no problem. It depends upon keeping it away from big motors and other things that generate noise, on having solid grounding, etc. Most people seem to consider RS232 at 9600 as being OK for just about anything inside a single building. I'm sure somebody from the Pentagon is going to tell me that they have to use microwave with 2 repeaters to get from one end of their building to the other, but for buildings of the size used in universities, things work. You should not use RS232 -- or any other wire -- between buildings, because lightning will tend to fry the equipment that is connected to it. Also, slight differences in ground may cause surprising large currents to flow in the cable. You want to use fiber between buildings.