Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!uhccux!robin
From: robin@uhccux.uhcc.Hawaii.Edu (Robin Amano)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Serial-port connections
Message-ID: <8978@uhccux.uhcc.Hawaii.Edu>
Date: 13 Aug 90 19:33:01 GMT
References: <54123@iuvax.cs.indiana.edu>
Reply-To: robin@uhccux.UUCP (Robin Amano)
Organization: University of Hawaii
Lines: 22

In article <54123@iuvax.cs.indiana.edu> bobmon@iuvax.cs.indiana.edu (RAMontante) writes:
>"How long is a serial port?" Or, more accurately...my cousin has a dumb
>device with a serial port (connected to some relays), and he'd like to
>control the device remotely from his P.C.  My question is, how far can
>the remote device be from the the P.C., and how should it be connected?
>Would a "null modem" cable be reliable over a 200-foot span?  If not,
>what's the cheapest connection?  We thought of two modems and some phone
>wire; would the phone wire need to be powered then?  (300-baud would be
>good enough; it's not a high-speed device out there.)

RS232C standard limits cable lengths to 50 feet.  But, that's just the 
required standard.  Here at UH and at a private computer firm I used to 
work at we exceeded that length by far.  Infact, if you don't mind 300
baud you can easily run a 200-foot length, actually you might still be 
able to run at 9600 baud depending on your terminal.  We have a few lines
here at UH over 500 feet, some use line drivers and run at 9600 and some
are satisfied with nothing and run at 1200 baud - and these are non-shielded
solid conductor telephone cable.  If I were you I would get shielded cable
and try it without any modem or line driver.  I think you'll probably be 
able to go 9600 or 2400 at the least, but since you don't mind a slow 300
I can almost guarantee you that it'll work!  Although nothing is ever
guaranteed in this world.