46
40-400-00001, Rev. A
Twisted pair
Twisted pair insulated copper wire is used extensively in the telco network to support
analog-grade communications, such as the type of wiring generally supplied to serve a local
loop for a home. Twisted pair is normally .035-.016 inches (22-26 AWG). This type of facility
is used by the telco to supply ISDN BRI to an individual or centrex subscriber.
U Interface
A two-wire interface required by the FCC (not the ITU-T) between the Local Exchange
Carrier and the customer’s NT1. Specification completed during 1Q87 by ANSI T1D1.3.
X.25
ITU-T recommendation specifying how user equipment (DTE) is to connect to a public,
packet-switched network (DCE). Specifies Layer 1, 2, and 3 Protocols.