[c-nsp] PA-T3 vs. PA-T3+

[Gert Doering]

Hi,

this is one of the questions that comes up every now and then, but I
haven't seen the answer yet...

Are the exact differences between the PA-T3 and the PA-T3+ documented
anywhere?

I know that they are different regarding subrating/scrambling and
compatibility with non-Cisco DSUs (Kentrox etc.) on the other end.

But what I found yesterday seems to suggest that the electrical
specifications of the receiver and/or transmitter are different as well.

Reasoning: I have a customer T3 that will work perfectly on a PA-T3+
(no errors over many weeks).  Moving the T3 to a PA-2T3, it will become
very unstable (about 10% packet loss, CRC errors, framing errors, etc).

So I assumed "the PA-2T3 is broken" and swapped it with a spare PA-2T3 -
imagine my surprise when the customer T3 didn't work on that port either.

So I took the "broken" PA-2T3, connected a different T3, and ran some
"sweep range of sizes" tests on it - everything worked perfectly.

Summary:

  - a given T3 line works only on a PA-T3+, but not on PA-2T3s
  - given PA-2T3s work flawlessly with a different T3

-> the only way I can explain this is "the customer T3 line is somehow
different from the other T3 lines" (stronger or weaker signal, or maybe
something else?) and the tolerance range of the PA-T3+ is higher.

Anyone?

gert


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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de