Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!brutus.cs.uiuc.edu!psuvax1!ukma!david From: david@ms.uky.edu (David Herron -- One of the vertebrae) Newsgroups: comp.dcom.lans Subject: Re: Why Ethernet-over-twisted-pair, anyway? Keywords: Ethernet, twisted pair, cost-benefit Message-ID: <13392@s.ms.uky.edu> Date: 2 Dec 89 21:09:22 GMT References: <4645@blake.acs.washington.edu> <693@rsiatl.UUCP> <843@n3dmc.UU.NET> Reply-To: david@ms.uky.edu (David Herron -- One of the vertebrae) Organization: U of Kentucky, Mathematical Sciences Lines: 52 As Henry pointed out, UTP has an advantage when there's already that sort of wiring in place. A lot of places were wired with "extra" phone wiring under the assumption that something computerish would be able to make use of it. It turned out to be a bit of a self fulfilling prophecy -- the vendors saw all this extra wiring (and possibly were a source of advice for some people that the "extra" phone wiring would be useful Real Soon Now) and did networking on it. Now, why is a wiring scheme which was designed for the unique problems of analog circuitry going to be useful for digital circuitry? I don't know, someone want to tell me? As I see it -- without the shielding the cabling is going to affect more of the wiring around it and will in turn be affected more by the wiring around it. There will be crosstalk between adjacent wires. There will be more radio interference in the air -- something which people (pregnant women especially) have been up in arms over in recent years. Are the power levels low enough that the signals aren't measurable beyond the cabling? If so then how is the signal strong enough for the components on the network to deal with them? (that is, make out the signal in the noise from other sources (radio stations and the like)...) Heck, how does the power emmissions from the unshielded cable compare to those of the 100,000 watt FM station a couple miles away or the high tension power wiring ? These are the things I'm worried about with it.. If those concerns, and other related concerns, can be answered adequately then I think there's not much room for complaint. In my old job @ ms.uky.edu we used a combination of thin wire and thick wire coax with appropriate repeaters between segments (DEBET's and DEMPR's). There weren't *any* problems, not even the one that the campus communications guy claimed you have with thin coax pulling out of the systems and bringing down the network. In our case when the building was designed an extra set of conduits was run which was intended for some sort of intercom system which was never installed. So we used that for both our serial and ether cabling. In my new job all the wires look like phone wires. But then that's one of the side effects of working at a phone company (AT&T)... :-) -- <- David Herron; an MMDF guy <- ska: David le casse\*' {rutgers,uunet}!ukma!david, david@UKMA.BITNET <- <- New official address: attmail!sparsdev!dsh@attunix.att.com