Xref: utzoo comp.dcom.lans:971 comp.dcom.modems:1283
Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!aurora!labrea!Shasta!kaufman
From: kaufman@Shasta.STANFORD.EDU (Marc Kaufman)
Newsgroups: comp.dcom.lans,comp.dcom.modems
Subject: Re: Fluorescent lights and data cables
Message-ID: <2442@Shasta.STANFORD.EDU>
Date: 29 Jan 88 02:28:20 GMT
References: <5253@columbia.edu>
Reply-To: kaufman@Shasta.stanford.edu (Marc Kaufman)
Organization: Stanford University
Lines: 28

In article <5253@columbia.edu> desimone@frodo.columbia.edu (Sal Desimone) writes:

>Hi...we're in the process of specifying a preliminary wiring plan for a new
>	building.  The architects have given us a cable-routing scheme 
>	utilizing cable trays along hall-way walls.  Their scheme seems
>	acceptable to us except for one point:  the cable trays will be mounted
>	in an aluminum tray above the hallway lights (they are flourescent,
>	I believe).  The question I have is will the fluorescent lights
>	cause interference along the data lines?

Boy, can they ever!  Fluorescent lamps in commercial buildings are often
run on 208 volts, 288 volts or higher.  If you must run RS-232 above
such fixtures, 1) use fully shielded cable, 2) use line drivers for noise
reduction if running any distance.

>	                                          Is the aluminum tray
>	an adequate shield? 

No.  No more than the fixture case itself.  However, if it can be used
to give you more space between the data cable and the fixture, that will
help.

I used to own a Protocol Converter company, and had to help customers find
problems.  In a large number of noise cases, the data cable was routed
overhead and just thrown over the light fixtures.  You should always
try to keep low level signals away from them.

Marc Kaufman (kaufman@Shasta.stanford.edu)