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From: pozar@hoptoad.UUCP
Newsgroups: comp.dcom.telecom
Subject: Re: Submission for comp.dcom.telecom (Use of shielded cable for telephones)
Message-ID: <2188@hoptoad.uucp>
Date: Tue, 26-May-87 00:10:44 EDT
Article-I.D.: hoptoad.2188
Posted: Tue May 26 00:10:44 1987
Date-Received: Thu, 28-May-87 01:48:03 EDT
References: <8705230318.AA03545@seismo.CSS.GOV>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: hoptoad!pozar@ucbvax.Berkeley.EDU (Tim Pozar)
Distribution: world
Organization: Syncstream (San Francisco)
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Approved: telecom@buit1.bu.edu


In article <8705230318.AA03545@seismo.CSS.GOV> kitty!larry@SEISMO.CSS.GOV writes:
>In a recent article dbj@RICE.EDU (Dave Johnson) writes:
>> I need to wire a new phone line through a house for use with a modem.
>> Is there some kind of sheilded phone cable that I could use to help
>> reduce any noise in the connection?  Anything else I should be aware
>> of when routing the wire such as not getting too close to electrical
>> wires?  Thanks.
>
>	I can think of no valid reason to use shielded telephone cable

   I can give you one reason:
   RFI or Radio Frequency Interference.
   I spec'ed a Northern Telecom SL-1 (s series) for our AM station in San Jose.
I knew at that time there was some pretty nasty RF levels in the building and 
cofermed them with a RF field strength meter.  200volts per meter!  The 
building contains a 50Kw transmitter and sits in the main lobe of the direc-
tional.  When we spec'ed the SL-1, I told Pac Tel (the folks we were
purchasing the switch from) that they would be encountering some high RF and 
shielded, twisted pair would be advisable when installing the sets.  They said,
"No problem", and instaled unshielded, twisted pair.  Boy did they lose money
on our purchase!  They had to not only reinstall shielded, twisted pair, but
drop .01uf caps on all the lines and ferrite beads!
   Now I relize that most houseing will not be right next to a 50,000 watt 
AM radio station, but if you are one of the small unfortunate RFI can be 
handled with shielded wire and mabey a couple of .01uf caps.


-- 
        Tim Pozar
UUCP    pozar@hoptoad.UUCP
Fido    125/406
USNail  KLOK-FM
	77 Maiden Lane
	San Francisco CA 94108