ADTRAN Express L128T S User Manual page 187

two-wire circuit
A transmission circuit composed of two wires, signal and
ground, used to both send and receive information. In con-
trast, a 4-wire circuit consists of two pairs. One pair is used to
send and one pair is used to receive. All trunk circuits (long
distance) are 4-wire. A 4-wire circuit delivers better recep-
tion, but also costs more. All local loop circuits (those coming
from a Class 5 central office to the subscriber's phone system)
are 2-wire, unless a 4-wire circuit is requested.
U-interface
A twisted pair subscriber loop that connects the NT1 refer-
ence point to the ISDN network, as defined in the I.411 Rec-
ommendation. This interface provides Basic Rate Access with
an operating frequency of 160 kbps and an information rate of
144 kbps. Under U.S. regulations, this also marks the line of
demarcation between customer-owned equipment and the
public network.
ZIP
Zone Information Protocol. The AppleTalk session-layer pro-
tocol used to maintain and discover the internet-wide map-
ping of network number ranges to zone names.
Zombie Routes
Routes that have been identified by the router to be deleted.
They remain in the router's route table for a specified amount
of time with an infinite metric so that all other routers will
learn of this router's intention to delete them.
61202070L3-20 Express L128T S/T User Manual
Glossary
Glossary-9