🚀 go-pugleaf

In article <NEWTNews.820626346.32539.jrhodes@jrhodespc.nwest.mccaw.com> jrhodes@jrhodespc.nwest.mccaw.com writes:
>Path: news.internetMCI.com!darwin.sura.net!news.dfn.de!news.ruhr-uni-bochum.de!news.uni-stuttgart.de!rz.uni-karlsruhe.de!blackbush.xlink.net!howland.reston.ans.net!newsfeed.internetmci.com!in1.uu.net!winternet.com!news.minn.net!skypoint.com!hagar.cyberop
>ics.com!bpeters!c1mpls!nwestnews.nwest.mccaw.com!usenet
>From: jrhodes@jrhodespc.nwest.mccaw.com
>Newsgroups: comp.dcom.telecom.tech,comp.dcom.isdn
>Subject: Re: Please critique: When is a B channel only 56K?
<snip>

Well, one reason for 56K B channels beyond what Fred said (which are 
technically correct) is that PACBELL uses its Switched 56 network to run ISDN 
data calls.  An excessive all 0's is not a condition to start a Yellow alarm, 
unless it causes a Red condition.  LOS (Loss of Signal) would occur first.

A Bi-polar violation does not start a T-1 AMI frame.  The framing pattern is 
locked onto by the framer.  BPV's are not ever good in T-1 AMI (unlike DDS - 
sometimes they are used to start loops).  FYI, B8ZS is not necesarily linked 
to ESF.  Both D4/B8ZS and ESF/AMI are possible.

Also, even though the 8th bit is used for signalling out of every 6th frame, 
you should not count on the other 5.  Depending on how your network is 
provisioned, the carrier may have to terminate the T-1 (like at a 1/0 DACS).  
This can cause "Signalling re-insertion".  This is used when a T-1 superframe 
is torn apart to re-align the signalling bits in the superframe.

Jim Sackman
Racal-Datacom
Manager, T-1 Access
Jim_Sackman@usa.racal.com