E

E3
     A digital circuit with standardized characteristics that operates at 34 Mbps. This standard is widely
    used in Europe for  inter carrier communications as the rough equivalent of a DS-3.

E.164
    A public network addressing standard utilizing up to a maximum of 15 digits.  ATM uses E.164
    addressing.

E-Link
    In SS7, a digital circuit that connects a service switching point (SSP) or  service control point (SCP)
    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
    Adding expanded 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.

Earth Station
     A satellite communications facility (a satellite dish and associated equipment) located on the earth's
    surface (or on a building,  ship or other mobile vehicle).

Echo Cancellation
     A technique used with voice circuits to isolate and filter unwanted signal energy which accompanies
     analog transmissions.

Echo Canceller
     A circuit feature that turns off the incoming signal while one end of the call is talking (to avoid an annoying
    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.

Edge Device
    A physical device which is capable of forwarding packets between legacy inter working interfaces (Ethernet,
    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
     An industry standard (ANSI X12, X.400) for direct computer-to-computer information exchange.

EFS - Error Free Seconds

Egress
     The method, time, circuit, or facility used to exit the network at the call destination.

ELAN - Emulated Local Area Network
    A 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 radio services
    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
     All circuit elements are digital. No modems are used to convert digital signals to analog at any point.

End-To-End Service
     Interexchange service that extends from one customer premise to another customer premise. It usually
    consists of the local  loops on each end and an IEC leg in the middle.

End Station
    These devices (hosts or PCs) enable the communication between ATM end stations and end stations on
    "legacy" LAN or among ATM end stations.

End User
     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.

Engineering
     The process or organization responsible for the skillful design, construction, maintenance and enhancement
    of complex or  sophisticated systems of hardware, software, processes, etc.

Enhanced Services
     Services using 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 data.

Entrance Facility
     A high-capacity 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 for
    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
    been segmented.

Enumeration List
     A finite collection that identifies all possible (allowable) values for a variable, field, data attribute, object type, etc.

Equal Access
     (AT&T Divestiture - 1982 Modified Final Judgment)  Describes a condition where telephone customers may
    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 AT&T.

Equal Charge Rule
     A rule contained in the 1982 MFJ which required BOCs to charge access rates that do not vary with the
    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  cable.

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
    is available.

Error-free Seconds
     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 defined
    in CCITT Recommendation  0.151.

ESF - Extended Super Frame
An 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 control, and
maintenance capabilities.

Ethernet
     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.

Event
     A milestone, a signal, the completion of something that is of interest to an object, a process, or a system.

Event Driven
     A system of cooperating objects that responds as things happen in real-time. (Contrast with Batch-Oriented)

Exchange
    1. An installation which allows telecommunications routes to be connected to each other (often called a switch).
    2. A switching center (i.e. central office, PBX, etc.).

Exemption Certificate
     A written 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.

Expedite
     A formal process of diverging from normal processing procedures to accelerate the handling of a high-priority
    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.

Express Circuit
     A carrier circuit set up between two cities without multiplexing equipment, thus simplifying the provisioning process.