North American Network Operators Group|
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Re: Clear Channel on a T1
Good point, Phil. I believe that the modern T1 spec states that a maximum or 45 zeros can be sent before the CSU will inject a '1'. I don't have a spec handy to verify it.
Of course, with B8ZS, you'll never approach this long string of zeros on the line, so it's a moot point. B8ZS replaces eight zeros with 4/4 ones/zeros, in a known bipolar violation pattern. This will insure that ones' density is met on the line, and the circuit endpoints can replace the injected ones with eight zeros and restore the bit patterns of the modified DS0s.
It's also the source of grief when a telco provisions one segment of a T1 circuit without B8ZS. When this non-B8ZS segment sees too many zeros, ones will be injected in the stream, corrupting the data.
Of course, this NEVER happens anymore...right? ;-)
From: Phillip Vandry <vandry@TZoNE.ORG>
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