E1 is a name for 2048 Kbit/s transmission link which consists of G.704/G.703 etsi specification protocols. If you need more document about this protocols, let me know, I can send it to you by email, or you can find them on the web site http://www.etsi.org
again, E1 is a name for 2048 Kbit/s transmission line which consists of 32 timeslots, you can place on this line any other protocols which occupy less then 2M.
alex
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