Date: Tue, 06 Nov 2001 15:03:29 -0500 From: "Robert E. Johnson, P.E." <bob@eng.ufl.edu> To: wmoran@potentialtech.com Cc: questions@freebsd.org Subject: Re: Welders causing dial-out to fail Message-ID: <3BE84211.88CBE92D@eng.ufl.edu>
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> > Date: Tue, 06 Nov 2001 14:20:44 -0500 > From: Bill Moran <wmoran@potentialtech.com> > Subject: Re: Welders causing dial-out to fail > > In response to a few other similar responses, I thought I'd throw in some > more details: > The proxy server is physically located in the wiring closet where the phone > lines are. There is only about 5' of phone line from the proxy to the main > telco jack. The welders are on the other side of the building: > > telco conn. > +-----+-----+-------------------------+ > |proxy| | | > +-----+ | | > | | | > | | | > | office | | > | | | > | | | > +-----------+ | > | | > | welders | > | | > +-------------------------------------+ > > I don't know whether this may mean different things to different people, > but it doesn't (from my viewpoint) seem to support the "shield the wire > from proxy to telco will solve the problem" angle. If you can hear any noise from the welders in the phones, it is enough to cause at least some problems for the modems, so working on the phone line may help, even though it is very short. It may also be that the noise is coming in through the power system, although that would sort of require that there be some powered phone system equipment to feed it into the phone line. I doubt that it is getting into the phone line through the computer power supply. It is conceivable that the phone line is run close to a power line and picking up noise that way. If you have the phone line bundled with power lines for neatness, try moving it several inches away from them. Also, if you _do_ decide to try shielded phone line, the usually recommended installation is to connect the shield to the ground rod at the phone company access point, but don't connect the shield to anything else. Finally, this could be caused by a bad ground on either the power wiring for the building, or the phone system. Have both of them checked. They _should_ share the same ground system, but they might not. > The ceiling of this place is metal girders, and some of the electrical > runs through the ceiling, so I'm wondering if the ceiling is getting > charged or something and acting like a huge antenna that just transfers > the interference throughout the rest of the building. Not so much like an antenna, but a transmission line. Once the noise gets into the power line, it travels just like phone signals travel through the phone line. Anything connected to the same power system may pick up the noise. > > This may be an interesting problem to solve ... I've got a lot of ideas > to try, so thanks to everyone for the suggestions. > > - -Bill > Good luck, - Bob To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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