Article 5528 of comp.dcom.telecom.tech:
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From: fgoldstein@bbn.com (Fred R. Goldstein)
Newsgroups: comp.dcom.telecom.tech
Subject: Re: SDX PDH TRANSMISSION
Date: Fri, 20 Jan 1995 14:35:53 LOCAL
Organization: Bolt Beranek & Newman Inc.
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References: <3fonpb$270@hobbit.gandalf.ca>
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In article <3fonpb$270@hobbit.gandalf.ca> NBROUGH@ursa.gandalf.ca writes:

>CAN ANYONE PROVIDE ME WITH INFORMATION AS TO WHAT SDX AND PDH TRANSMISSION
>ARE.
>THANKS NICK BROUGH.

Do you, perchance, mean "SDH" and "PDH"?

PDH is Plesiochronous Digital Hierarchy, the ITU-T name for the "traditional"
digital transmission series E1/E2/E3/E4 and I think T1/T2/T3.  It's in G.703.

SDH is Synchronous Digital Hierarchy, the ITU adaptation of SONET.  It's in
G.707-709.

___
Fred R. Goldstein   k1io    fgoldstein@bbn.com
Bolt Beranek & Newman Inc., Cambridge MA  USA   +1 617 873 3850
Opinions are mine alone; sharing requires permission.