🚀 go-pugleaf

In <tsw-0801961308380001@cypher.3do.com>, tsw@3do.com (Tom Watson) writes:
>In article <4cec6n$fm7@mercury.near.net>, fgoldstein@bbn.com (Fred R.
>Goldstein) wrote:
>
>> 
>> A conformant CSU for "AMI" (better known as AMI/ZCS, for Zero Code
>> Suppression) coding will  NEVER send the 15 zeroes, and WILL insert
>> a zero if the source doesn't conform.  Thus the alarm means the CSU
>> is not working or connected -- a disconnected wire looks like a
>> string of zeroes, no?
>> 
>
>Isn't B8ZS where AMI violations are put in when it senses 8 zeros.  The
>receiver then notices this and puts the zeros back to the channel unit.
>
>The violations were: 0++00--0 and 0--00++0 depending upon the previous bit
>signalled.
>

Tom,

You have it right.  Fred is addressing the case of an older span that 
has not yet been converted to B8ZS.  In this case the customer's CSU
is responsible for forcing ones into every 8-bits if his other 
equipment fails to do so (the old no-harm-to-the-network philosophy).

Since you might have a one at the beginning of one 8-bit channel, and
at the end of the next, you could have up to 15 zeros in a sequence. 
T-1 equipment sends an alarm condtion if there are more than 15 ones 
in sequence.

Laurence V. Marks
IBM Corp. - Research Triangle Park, NC