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Path: utzoo!utgpu!water!watnot!watmath!dalcs!aucs!wdw
From: wdw@aucs.UUCP
Newsgroups: comp.dcom.modems
Subject: Re: Reliability of Modular Jacks
Message-ID: <287@aucs.UUCP>
Date: Tue, 24-Feb-87 13:06:22 EST
Article-I.D.: aucs.287
Posted: Tue Feb 24 13:06:22 1987
Date-Received: Wed, 25-Feb-87 19:40:18 EST
References: <267@aucs.UUCP> <299@mtxinu.UUCP> <796@fmsrl7.UUCP> <625@infinet.UUCP>
Reply-To: wdw@aucs.UUCP (Bill Wilder)
Distribution: na
Organization: School of Computer Science, Acadia Univ., Nova Scotia
Lines: 33
Keywords: RJ-11, RJ-12, RJ-45, RS-232

At the request of our engineer I posted the original query about the
advisability of Modular jacks for terminal connections. Several replies
mentioned the possible electrical hazard (to people or machines) if the
wrong device is connected to the wrong jack. I enclose the following
findings from our engineer.


  |I have made some measurements this morning and found the following:
  |
  |These are not theoretical values, but actual measurements.
  |
  |  - Normal idle state of the phone line:  50V DC - If I put my fingers
  |  across the line, I am not able to feel the voltage.
  |
  |  - Ringing voltage is 82V RMS which is 100V Peak to Peak AC. If I put
  |  my fingers on the line while it is ringing, I am able to feel a
  |tingling feeling.
  |
  |  - The frequency of the ring is 33 Hz. It is a clean looking Sine
  |  wave.
  |
  |  - One side of the line is tied to ground. Therefore measurements from
  |one side of the line to ground are the same as measuring across the
  |line.  The other side to ground always measures near zero volts.

We have decided to use six-wire modular jacks (two jacks per faceplate)
with both jacks wired in parallel. We'll use the inner pair for the phone
connection and the outer two pair for the terminal connection. This should
allow either device to be plugged into either jack with no harm to either.
-- 
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