Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uunet!europa.asd.contel.com!seka.scc.com!enger
From: enger@seka.scc.com (Robert M. Enger)
Newsgroups: comp.dcom.modems
Subject: Re: Line Noise Redux
Keywords: Line Noise
Message-ID: <1991Jan23.175006.13163@europa.asd.contel.com>
Date: 23 Jan 91 22:50:05 GMT
References: <1991Jan13.183631.27081@europa.asd.contel.com> <59437@aurs01.UUCP> <1991Jan20.204546.5398@europa.asd.contel.com> <59468@aurs01.UUCP>
Reply-To: enger@seka.scc.com
Organization: CONTEL Federal Systems
Lines: 41
Nntp-Posting-Host: seka.scc.com

In article <59468@aurs01.UUCP>, luce@aurs01.UUCP (J. Luce) writes:
|> -You mentioned that you were feeding into a SLIC.  
|> 
|> I was moved completely off the SLIC to a different frame. *NOW* the
|> SoBell people tell me I am on a No. Telecom DMS-100 digital rather the
|> aforementioned AT&T analog switch.
|> 
|> 
|> -If that unit is close by, perhaps its possible that you're 
|> -overdriving its input.  You might want to try padding down (REDUCING)
|> -the output level of your modem to see its effect.
|> 
|> I am quite a ways away and go through a 'box' containing T1 cards onto a
|> fibre down to the C.O. I am about 2 miles from the T1.
|> 

Hello again:

The "box' containing the T1 cards and a fiber connection IS THE SLIC.
The slic not only contains T1 cards, it also contains subscriber
interface cards.  The subscriber (station line) interface card that
you are connected to in that "slic" MAY BE BAD, or improperly configured.

Another problem affecting your performance may be an improperly 
installed loading coil.  Telco installs equalization coils on subscriber
lines more than so-many miles in length.  (the figure I got while asking
around the office was about 1-1/2 miles, which would qualify your
circuit).  Coils are used to smooth the frequency response for voice
use, but play havoc with the phase response of the circuit.  
As a side note, telco removes such coils from cable pairs used for
Digital Dataphone Service (DDS) digital data circuits.  

I hope you get to the bottom of this problem.  And when you do,
please post/e-mail the cause/remedy info to us.  Thanks!

Bob

---
Robert M. Enger
CONTEL Federal Systems
enger@seka.scc.com  (Internet)