E & M signaling – Method of receiving and transmitting signals. (Originally stood for ear and mouth).
External Binary Coded Decimal Interchange Code (EBCDIC) – A transmission system used by several IBM and IBM-compatible data terminals which consists of eight data bits, each of which represents a particular number, letter or character.
Echo – A distortion that occurs when a signal is reflected or otherwise returned (on the same wire on which the speaker is speaking) with sufficient magnitude and delay as to be perceived by the speaker. [Typically, a problem on satellite circuits.]
Echoplex - A method of checking and compensating for echos in network terminals that are operating in the two-way simultaneous mode.
Edit – (1) To prepare data for a later operation. (2) Functions such as the rearrangement or the addition of data, the deletion of unwanted data, format control, code conversion and the application of standard processes such as zero suppression.
Electronic key telephone set (EKTS) – Any key telephone with a built-in microprocessor which allows access to PBX-like features as well as access to multiple CO lines and uses two- to four-pair wiring.
Electronic mail – (1) The electronic transmission of letters, messages and memos from one computer to another. (2) A computer-aided method of communication where an individual sends an on-line message to another individual via dial-up or dedicated access. See Bulletin Board.
Electronic switching system (ESS) – Electronic versus electromechanical switching equipment.
Electronic tandem network (ETN) – (1) A private network in which the network switch functions as a PBX and automatically connects the calling office to the called office through tandem-tie trunks.
Emulate – (1) To imitate another system. (2) A method by which an imitating system can accept the same data, execute the same computer programs and achieve the same results as the original system.
Enable – (1) To prepare a circuit for operation. (2) To allow an item to function.
Encoding – (1) Inscribing or imprinting Magnetic Ink Character Recognition (MICR) characters on checks, deposits and other documents to be processed by a MICR reader. (2) The introduction of data on a medium such as a magnetic strip on plastic cards.
Encryption – Conversion of data into code form for security purposes during transmission and decoding at the receiving end.
End office (EO) – A switching center where subscriber lines are terminated and where toll calls are switched through to the terminating destination.
Enterprise number – (1) A unique telephone exchange number that permits the terminating party to be automatically billed for incoming calls. (2) A toll-free number.
Epitophier – A small piece of plastic located below each jack on a communications outlet. The color of the plastic indicates the type of service that may be provided on the jack.
Equal access (EA) – (1) The concept — enforced by the 1984 Modified Final Judgement (MFJ) — that all Interexchange Carriers (IXC) must have the same access to the local BOC facilities as AT&T enjoys; provided as Feature Group D interconnection. (2) The arrangement whereby the BOCs provide trunk side connections to an End Office (EO), Automatic Number Identification (ANI), answer supervision, dial pulse or DTMF signal recognition. [Customers may subscribe to the IXC of their choice.]
Equalization – (1) Procedure to compensate for fluctuation in circuit amplitude, delay or distortion and to produce a flat frequency response rate. (2) In data communications, a compensation for the increase of attenuation within frequency.
Ergonomics – A discipline that promotes the consideration of human factors in the design of a working environment and its components (heat, light, sound, equipment).
Erlang - (1) A unit of traffic intensity. (2) One erlang is the intensity at which one traffic path would be continually occupied.
Error - (1) A difference between a computer value and the theoretically correct value. (2) A malfunction that is not reproducible. (3) In data communications, any unwanted change in the original contents of a transmission.
Error burst – Results of an event that causes a lengthy stream of consecutively transmitted bits to be defective. [Retransmission is the normal correction procedure in the event of an error burst.]
Error rate – Ratio of the number of signal elements (or data) incorrectly received to the total number transmitted. (2) The probability of an error occurring during the transmission of a message.
Error-free seconds (EFS) – Ratio of the number of seconds in which there are no bits in error to the total number of seconds in the measurement interval.
Errored second (ES) – A one-second interval containing one or more errors. [Its reciprocal, Error Free Second (EFS), is the more commonly used term.]
Ethernet – A packet-switched data local area network (LAN) design by Xerox Corp. which employs CSMA-CD as access control mechanism.
Exchange (EX) – (1) A room or building equipped so that telephone lines terminating there may be interconnected as required. The equipment may include manual or automatic switching equipment. (2) A telephone switching center; an aggregate of traffic-carrying devices, switching stages, controlling and signaling means at a network node that enables subscriber lines and/or other telecommunication circuits to be interconnected as required by individual callers. (3) The territory served by an exchange, within which local service rates apply; also known as the exchange area or local service area.
Extended superframe format (ESF) – Use of the Cyclical Redundancy Check-6 (CRC-6) Code to measure actual logic errors rather than format errors. [ESF permits circuit performance to be measured in-service and real-time, regardless of the electrical/physical characteristics of the transmission facility and network. Error data processed and stored in the ESF CPU is available on demand for the last 24 hours in 15-minute intervals, making it possible to sectionalize problems.]
Extract – A data synopsis from a given system which is passed to another system to complete processing.