Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request
From: syd@dsinc.dsi.com (Syd Weinstein)
Newsgroups: comp.dcom.telecom
Subject: Re: LADS Circuits
Message-ID: <2322@accuvax.nwu.edu>
Date: 21 Dec 89 01:51:51 GMT
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X-Telecom-Digest: Volume 9, Issue 585, message 8 of 13


jst@cca.ucsf.edu (Joe Stong) writes:

>I would like to hear of people's experiences with LADS (solid copper 4
>wire or 2 wire circuits only for sites local to the same central
>office).  In particular, I'm curious about what you can get through
>them in the way of frequency response.

We had a LADS circuit of about 4 mile length for several years.  I
have plenty of experience.  They are a 4 wire metalic connection with,
if connected properly, sealing current on the line.  Sealing current
on LAD circuts is a relatively new item (couple of years) so not all
have it, and if you don't get it converted.  It cut our service calls
from one per week to almost never.  (And they did the conversion for
free, just to save on their service calls)

Ok, here is what it can do: Send a audio signal end to end, with about
a 12Khz bandwidth.  Why: transformers on both ends to trap the sealing
current.  In fact, they make special modems for LAD circuits.

Those modems can do 19200 for about 1 mile, 9600 for about 3-4 and
1200 for about 12-20.  In our case, we got 9600 to work pretty
reliabably.

There are strict standards as to what signals can be put on the line,
to avoid cross talk with the other normal pairs in the cable plant.

>My understanding at the moment is that T1 is delivered on a regular 4
>wire connection to one's building.  Are there equalization networks
>along the "subscriber loop" of a T1 that make it "better" than a LADS
>circuit?

T1 can be distributed on metallic, if you put regenerators ever so
often, and its not that far apart at T1 rates.  56KB can go farther
without regen, but even at 56KB, you probably will need one to go 6
miles.  Getting ARCnet to run is not too likely.  Remember to run T1,
you must run CSU's, and they are fixed rate.
 
=====================================================================
Sydney S. Weinstein, CDP, CCP                   Elm Coordinator
Datacomp Systems, Inc.				Voice: (215) 947-9900
syd@DSI.COM or {bpa,vu-vlsi}!dsinc!syd	        FAX:   (215) 938-0235