Re: 56k Required encoding
Dan Swartzendruber (dswartz@druber.com)
Sat, 26 Jul 1997 08:28:59 -0400
At 11:52 PM 7/25/97 -0500, you wrote:
>
>AMI is not a good choice for a data circuit, and I'm not sure the PM3 even
>supports it. It has been some time since I was around the details of
>this, but as I remember it, AMI does not have enough line transitions to
>allow proper clock recovery. Unless the line is very busy (to keep
>transitions high) you will get errors on the link. B8ZS forces a high
>enough line transitions rate through enforced bipolar violations to allow
>decent clock recovery, and should always be used on a data circuit.
This is incorrect. B8ZS will get you the maximum 1.544 mb/s data rate,
but AMI is perfectly usable (how on Earth do you think people used T1
circuits before B8ZS was available?) Using AMI, you can set each DS0
to be 56K instead of 64K. This gives you an aggregate 1.3 (approx) mb/s
data rate, with the proper one-bit density. Any decent T1 CSU/DSU will
allow you to configure this.
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Swartzendruber Consulting, Inc.