A digital circuit with
standardized characteristics that operates at 2.048 Mbps. This standard is
widely used in Europe and in submarine cables
as the rough equivalent of a DS-1 (E1 provides
64 Kbps channels - six more than a DS-1).
A digital circuit with
standardized characteristics that operates at 34 Mbps. This standard is
used in Europe for inter carrier
communications as the rough equivalent of a DS-3.
A public network addressing standard
utilizing up to a maximum of 15 digits. ATM uses E.164
In SS7, a digital circuit that
connects a service switching point (SSP) or service control point
to a designated pair of signal transfer points
(STPs) other than its home pair.
E&M Lead Signaling
Method of signaling
using dual connection ports ("E" and "M"). When a signal
reaches a switch, it
enters through the "E"
lead, and the switch then sends it out through the "M" lead.
EAS - Extended Area Service
local area service to local calling area. Usually a flat monthly fee
is charged. For
example, a Vancouver business
adding the Portland area to avoid the long distance charges.
communications facility (a satellite dish and associated equipment) located
on the earth's
surface (or on a building, ship
or other mobile vehicle).
A technique used
with voice circuits to isolate and filter unwanted signal energy which
A circuit feature that
turns off the incoming signal while one end of the call is talking (to avoid
long distance echo). It must be
disabled for Full Duplex (simultaneous 2-way calls). An echo canceller
does not turn off the voice channel, as stated,
but electronically removes unwanted echo, while maintaining
a full-duplex channel. An echo suppresser
disables the channel in one direction or the other, depending on
who is talking. Echo cancellers must be disabled for
some types of high speed modems calls, and must
also be disabled for "clear channel" data calls, such as ISDN.
A physical device which is
capable of forwarding packets between legacy inter working interfaces
Token Ring, etc.) and ATM interfaces based
on data-link and network layer information; but, which does not
participate in the running of any network layer
routing protocol. Obtains forwarding descriptions using the
route distribution protocol.
EDI - Electronic Data Interchange
industry standard (ANSI X12, X.400) for direct computer-to-computer
EFS - Error Free Seconds
The method, time, circuit, or
facility used to exit the network at the call destination.
ELAN - Emulated Local Area Network
logical network initiated by using the mechanisms defined by LAN
emulation. This could include
ATM and legacy
attached end stations.
Email - Electronic Mail service (generic term)
A method of transmitting letters, memos or other
communications via electronics rather than the conventional
method of paper.
EMI - Electromagnetic Interference
Equipment used in high speed data systems, including ATM, that generate and
transmit many signals in the
radio frequency portion
of the electromagnetic spectrum. Interference to other equipment or
may result if sufficient power from
these signals escape the equipment enclosures or transmission media.
End Office - EO
Class 5 Central
Office Switch owned and operated by a LEC.
End-To-End Digital Transmission
circuit elements are digital. No modems are used to convert digital signals
to analog at any point.
service that extends from one customer premise to another customer premise.
consists of the local loops on each
end and an IEC leg in the middle.
These devices (hosts or PCs)
enable the communication between ATM end stations and end stations on
"legacy" LAN or among ATM end stations.
A person who uses (but does
not necessarily pay for) products and services, (e.g. a person called by a
paying customer). Users are usually people, but
could also be computers, objects, switches or other types
of computer systems or communication equipment.
The process or
organization responsible for the skillful design, construction, maintenance
of complex or sophisticated
systems of hardware, software, processes, etc.
network facilities and computer processing that:
(1) act on the format, content, code, protocol
or similar aspects of transmitted information;
(2) provide additional or restructured information; or
(3) involve subscriber interaction with stored
circuit (such as DDS, DS-1 or DS-3), between the LEC's Central Office and
the IEC's Point
of Presence to support a
customer's dedicated local access. There is a recurring charge rate element
each entrance facility.
Entry Border Node
The node which receives a
call over an outside link. This is the first node within a peer group
to see this call.
End of Message - EOM
An indicator used in
the AAL that identifies the last ATM cell containing information from a data
packet hat has
A finite collection
that identifies all possible (allowable) values for a variable, field, data
attribute, object type, etc.
(AT&T Divestiture -
1982 Modified Final Judgment) Describes a condition where telephone
choose the carrier of their
choice by dialing 1+ the long-distance number, and using the same number of
dialed digits regardless of which long distance
company is chose. The MFJ and the FCC require local
exchange carriers to provide equal access (most
central offices now have this capability). Equal Access
may also refer to a more generic concept under which
the BOCs must provide access services to AT&T's
competitors that are equivalent to those provided to
Equal Charge Rule
A rule contained in
the 1982 MFJ which required BOCs to charge access rates that do not vary
volume of traffic.
Erbium-Doped Optical Amplifier - EDOA
High-performance optical fiber amplifiers capable of reducing the number of
regenerators needed over a
span of fiber optic
Erlang - Traffic Unit - (1 Erlang = 3600 Calling Seconds = 36 CCS)
An international unit of average traffic on a
facility during a period of time (usually a busy hour). The number
of erlangs is the ratio of the time the
facility is occupied (continuously or cumulatively) to the time the facility
A measure of the
quality of the signal being transmitted. It is a percentage representing the
total amount of
time over a 24-hour period that
the signal contained bit errors and it is calculated using a test pattern
in CCITT Recommendation 0.151.
ESF - Extended Super Frame
enhanced version of D4 formatting, and it is the current industry standard.
ESF is a DS-1 framing format
composed of 24
DS-0 time slots of 192 bits each, plus a coded framing bit, and organized
into a superframe.
ESF provides 16 signaling
states in the 193rd bit to ensure synchronization, supervisory
A LAN and data-link protocol
based on a packet frame. Usually operating at 10 Mbps and over shielded
coaxial cable or twisted pair telephone wire,
allows multiple devices to share access to the link.
A milestone, a signal, the
completion of something that is of interest to an object, a process, or a
A system of cooperating
objects that responds as things happen in real-time. (Contrast with
1. An installation which allows
telecommunications routes to be connected to each other (often called a
2. A switching center (i.e. central office,
customer designation that certifies that its dedicated facility should be
exempt Special Access Surcharge.
Exit Border Node
The node that will
progress a call over an outside link. This is the last node within a
peer group to see this call.
A formal process of
diverging from normal processing procedures to accelerate the handling of a
request (usually at a higher cost
to the requester).
Explicit Forward Congestion Indication - EFCI
An indication in the ATM cell header. A network
element in an impending congested state, or a congested state
may set EFCI so that this indication may be examined
by the destination end system.
A carrier circuit set
up between two cities without multiplexing equipment, thus simplifying the