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From: BRUCE@ccavax.camb.com (Barton F. Bruce)
Newsgroups: comp.dcom.telecom
Subject: Re: An Introduction to ISDN From the CERFnet News
Message-ID: <13087@accuvax.nwu.edu>
Date: 6 Oct 90 05:55:05 GMT
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X-Telecom-Digest: Volume 10, Issue 716, Message 4 of 12


In article <12979@accuvax.nwu.edu>, aspect!kevinc@uunet.uu.net (Kevin
Collins) writes:

> The current version of the standard has provisions for using 6 PRI
> B-channels together (called an H0 channel, 384 Kb/sec) and using 24
> B-channels together (H11 channel, 1.536 Mb/sec [this is AT&T's number,
> don't know why it's not 1.544Mb/sec]). AT&T offers a "Switched 384"

The 1.536 Mb/sec is 64kb x 24. The oft used 1.544 figure includes the
additional 8kb for the framing bit. Each 1/8000 of a second, the line
passes 192 bits of data (24 x 8) + one framing bit for a total of 193
bits.

Other than keeping frames in sync and defining the A and B signaling
frames (or more generally, where one is within the super-frame
format), the framing bit also (under ESF) can carry a small amount of
network managment data.