Digital Hierarchy

Committee T1 - Sponsored by the Alliance for Telecommunications Industry Solutions and accredited by ANSI for interoperability standards.
www.t1.org/

DCB's T1 Information - All you wanted to know about T1's but were afraid to ask.
www.dcbnet.com/notes/9611t1.html

EverythingT1.com - Offering T-1/T-3 information, glossary, FAQs, reference, Technical reports, news, messageboard, ISP lists and links.
www.everythingt1.com/

SONET/SDH Technical Summary - Defines SONET and SDH, and provides references to appropriate standards organizations.
www.techfest.com/networking/wan/sonet.htm

T-1 Carrier - Webopedia definition and links about T1.
webopedia.com/TERM/T/T_1_carrier.html

T1 T-extender - DCB's T1 repeater for customer-owned cable.
www.dcbnet.com/datasheet/textds.html