Epitaxy -EZTV


Actually, it's molecular beam epitaxy. A fabrication process for growing silicon wafers of exceptional quality. The process involves heating an element, or compound, in an effusion oven to a temperature sufficient to release some of the atoms. (It's not as extreme as vaporization, but the idea is much the same.) Some of the atoms , or molecules, are drawn in a linear beam into an intense vacuum chamber , where they are deposited on a substrate (i.e., foundation) silicon wafer, one atomic, or molecular, layer at a time. The yield is a wafer comprising films that can be measured in atomic, or molecular, levels of thickness , with each film being identical in structure to the substrate wafer. Molecular beam epitaxy was perfected by A.Y. Cho of Bell Telephone Laboratories. The fabrication process was invented in 1960 by Messrs. Kleimack, Load, Ross, and Theuerer of Bell Labs as the demand developed for layered semiconductors and semi-insulators of precise film thicknesses. Epitaxy has made possible the manufacture of high-speed transistors packed by the millions on silicon chips. It also is used in the manufacture of optoelectronics and high-speed magnetic storage devices.


Engineering, PLanning and ANalysis Systems. Software offered by Western Electric (now called AT&T Technologies) to help operating telephone company people run their business better.


Enterprise Profit Optimization. This is a new acronym. Companies previously doing EAI, CRM and ERM are now doing EPO. There's no reason to figure out what EPO means. By the time you do, they'll have another acronym. And you won't be able to figure out what that one does, either.


EPOC is an operating system developed by Psion and now owned by Symbian, the joint venture between Psion, Nokia, Ericsson, Motorola, and Panasonic. It is designed for small, portable computer-telephones with wireless access to the Internet and other information services. EPOC is an alternative to Microsoft's Windows CE for smartphones, PDAs, etc.


Ethernet Passive Optical Network. A passive optical network implementing Ethernet over the fiber. See BPON, APON, PON, ONU.


A liquid material that solidifies upon heat curing, ultraviolet light curing, or mixing with another material. Epoxy is sometimes used for fastening fibers to other fibers or for fastening fibers to joining hardware.


Expansion Port Network, which contains line and trunk ports of proprietary Avaya systems.


Enhanced Parallel Port. A new hardware and software innovation (and now a standard) which allows computers so equipped to send data out their parallel port at twice the speed of older parallel ports, i.e. those that came on the original IBM PC. The EPP conforms to the EPP standard developed by the IEEE (Institute of Electrical and Electronics Engineers ) 1284 standards committee. The EPP specification transforms a parallel port into an expansion bus that theoretically can handle up to 64 disk drives, tape drives, CD-ROM drives, and other mass-storage devices. EPPs are rapidly gaining acceptance as inexpensive means to connect portable drives to notebook computers. There's no difference in the shape of the ordinary, 25-pin D-connector plug/connector or the number of conductors. The Enhanced Parallel Port (EPP) was developed by Intel Corp., Xircom Inc., Zenith, and other companies that planned to exploit two-way communications to external devices. Many laptops built since mid-1991 have EPP ports. See also ECP.


Erasable Programmable Read Only Memory. A read only memory device which can be erased and reprogrammed. Typically, it is programmed electronically , but it is erased electromagnetically with ultraviolet light. EPROMS are typically returned to the vendor or factory for reprogramming. An EPROM on a graphics card might contain the default or ROM character set. EPROM chips normally contain UV-permeable quartz windows exposing the chips' internals. See also ROM and EEPROM.


An extension of the PostScript graphics file format developed by Adobe Systems. EPS lets PostScript graphics files be incorporated into other documents. FrontPage supports importing EPS files.


(Pronounced Ep-Sis.) Enhanced Private Switched Communications Service. An AT&T offering for large businesses with offices scattered all over the country. This service allows such businesses to rent space on AT&T electronic switches and join that switching capacity to leased lines. EPSCS customers get a network control center in their offices which gives them information on the continuing operation of their network and allows them some limited options for changing their services.


Enhanced Private Switched Network.


See Equalization, Equalizer.

Equal Access

All long distance carriers must be accessible by dialing 1 ” and not a string of long dialing codes. This is laid down in Judge Green's Modified Final Judgment (MFJ), which spelled out the terms of the Divestiture of the Bell Operating phone Companies (BOCs) from their parent, AT&T. Under the terms of this Divestiture, all long distance common carriers must have Equal Access for their long distance caller customers. City by city telephone subscribers are being asked to choose their primary carrier who they will reach by dialing 1 before their long distance number. All other carriers (including AT&T, if not chosen as primary) can be reached by dialing a five digit code (10XXX), thus providing Equal Access for all carriers. Not all long distance companies will opt for full equal access since this involves considerable expense to the local phone companies. See also Feature Group A, B, C and D.

Equal Access End Office

A central office capable of providing equal access. See also EQUAL ACCESS.

Equal Cost Multipath Routing


Equal Gain Combiner

A diversity combiner in which the signals on each channel are added together. The channel gains are all equal and can be made to vary equally so that the resultant signal is approximately constant.


A device inserted in a transmission line or amplifier circuit to improve its frequency response. An equalizer adds loss or delay to specific frequencies to produce a flat frequency response. The signal may then be amplified to restore its original form.


The process of reducing distortion over transmission paths by putting in compensating devices. The telephone network is equalized by the spacing and operation of amplifiers along the way. In recording, equalization is frequency manipulation to meet the requirements of recording; also the inverse manipulation in playback to achieve uniform or "flat" response. Also called Compensation. See equalizer and equalization circuit.

Equalization Circuit

A compensation circuit designed into modems to counteract certain distortions introduced by the telephone channel. Two types are used: fixed (com- promise) equalizers and those that adapt to channel conditions. U.S. Robotics high speed modems use adaptive equalization.

Equalizing Network

A device which is connected to a transmission path to alter the characteristics of that path in a specified way. It is often used to equalize the frequency response characteristics of a circuit for data transmission.

Equatorial Orbit

An orbit with a zero degree inclination angle, i.e. the orbital plane and the Earths' equatorial plane are coincident.

Equipment Cabinet

The metal box which houses relays, circuit boards or other phone apparatus. Usually also contains the power supply, which converts the 120 volt AC current into the low voltage direct current necessary to run the telephone system.

Equipment Cable

A cable or cable assembly used to connect telecommunications equipment to horizontal or backbone cabling systems in the telecommunications closet and equipment room. Equipment cables are considered to be outside the scope of cabling standards.

Equipment Compatibility

One computer system will successfully do the same thing that another computer will do with the same data. There are many levels of "equipment compatibility." The only true compatibility, however, is identical machinery. And identical means "identical" down to the very last chip and very last integrated circuit. We have found that some computers ” even those consecutively numbered ” do not always perform the same. We have empirically proven this for both IBM and AT&T computers.

Equipment Identity Register

See EIR.

Equipment Room

ER. A centralized space for telecommunications equipment that serves the occupants of the building or multiple buildings in a campus environment. An equipment room is considered distinct from a telecommunications closet because it is considered to be a building or campus serving (as opposed to floor serving) facility and because of the nature or complexity of the equipment that it contains.

Equipment Wiring Subsystem

The cable and distribution components in an equipment room that interconnect system-common equipment, other associated equipment, and cross connects.

Equipped For Capacity

The maximum number of lines and trunks that can be supported by the available hardware. It is not a totally effective measure of the size of a PBX. See Wired-For-Capacity.

Equivalent Four-Wire System

Transmission using frequency division to get full duplex transmission over only one pair of wires. Normally two pairs are needed for full duplex.

Equivalent Network

  1. A network that may replace another network without altering the performance of that portion of the system external to the network.

  2. A theoretical representation of an actual network.

Equivalent PCM Noise

Through comparative tests, the amount of thermal noise power on an FDM or wire channel necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM channel.


  1. Explicit Rate. The current mechanism for flow control in ATM networks. ATM RM (Resource Management) cells are circulated by the transmitting device, indicating both the current and the desired rates of transmission. Assuming that the receiving device is able to accommodate that desired rate without overflowing its buffers, the request is granted and is honored by all intermediate switches in the network.

  2. See Equipment Room.

Erasable Programmable Read-Only Memory


Erasable Storage

A storage device whose contents can be changed, i.e. random access memory, or RAM. Compare with read-only storage.

Erase Head

On a magnetic tape recorder ” voice or video ” this is the "head" which erases the tape by demagnetizing it immediately before a new recording is placed on the tape by the adjacent record head.


A rare earth element that when added to fiber optic cabling could obviate the need for repeaters every 20 miles on undersea cables and expand fiber optic cabling to capacities of trillions of bits a second. See Erbium-Doped Fiber Amplifier.

Erbium-Doped Fiber Amplifier



Easily Recognizable Code. ERCs are U.S. area codes with the same number in the second and third positions . Examples include toll free numbers (e.g., 800, 888, 877 and 866).

Erector Set Telecom

In North America, there's a children's game of building blocks called Lego. The game comes with hundreds of small plastic blocks, which can be assembled into all sorts of wonderful designs, from castles to gas stations . In England, Lego sets are also called Mecano sets. The generic term for Lego and Mecano sets is erector sets. The term "erector set telecom" is a concept created by Harry Newton as a way of explaining "the new open" telecommunications equipment, namely that you build your own computer telephony system from freely -available, non-proprietary hardware and software components. In short, a telecom industry along the same open hardware and software lines as the PC industry. History: A.C. Gilbert introduced the Erector Set in 1913 in the U.S. He went on to win 150 patents for a variety of inventions . His company, the A.C. Gilbert Company, created chemistry sets, microscope sets, and magic sets. Legos (from Denmark) came to the U.S. much later. The international LEGO Group was established in 1932 and is now one of the world's largest toy manufacturers, employing about 10,000 people in 50 companies in 30 countries . See Computer Telephony.


The science of determining proper relations between mechanical and computerized devices and personal comfort and convenience; e.g., how a telephone hand- set should be shaped, how a keyboard should be laid out.


  1. A measurement of telephone traffic. One Erlang is equal to one full hour of use (e.g. conversation), or 60 x 60 = 3,600 seconds of phone conversation. You convert CCS (hundred call seconds) into Erlangs by multiplying by 100 and then dividing by 3,600 (i.e. dividing by 36). Numerically, traffic on a trunk group, when measured in erlangs, is equal to the average number of trunks in use during the hour in question. Thus, if a group of trunks carries 12.35 erlangs during an hour , a little more than 12 trunks were busy, on the average.

    Erlang gets its name from the father of queuing theory, A. K. Erlang, a Danish telephone engineer, who, in 1908, began to study congestion in the telephone service of the Copenhagen Telephone Company. A few years later he arrived at a mathematical approach to assist in designing the size of telephone switches. Central to queuing theory are basic facts of queuing life. First, traffic varies widely. Second, anyone who designs a telephone switch to completely handle all peak traffic will find the switch idle for most of the time. He will also find he's built a very expensive switch. Third, it is possible, with varying degrees of certainty to predict upcoming "busy" periods. See also Erlang, A.K., Erlang B, Erlang C and Poisson.

  2. Erlang is also a programming language designed at the Ericsson Computer Science Laboratory. Open-source Erlang is being released to help encourage the spread of Erlang outside Ericsson. Ericsson has released, free of charge, a. The entire source code of the current Erlang system. b. The entire source code for Mnesia a distributed Database Management System, appropriate for telecommunications applications and other Erlang applications with need of continuous operation and soft real-time properties. c. Extensive libraries of code for building robust fault-tolerant distributed applications. All with documentation. All the above software has been battle tested in a number of Ericsson products, for example the new Ericsson ATM switch. See www.erlang.org.

Erlang, A. K.

In 1918, A. K. Erlang, a Danish telephone engineer, published his work on blocking in "The Post Office Electrical Engineers' Journal," a British publication. Like E.C. Molina, an AT&T engineer, Erlang assumed a Poisson distribution of calls arriving in a given time. Molina had assumed a constant holding time for all calls, whereas Erlang assumed an exponential distribution for holding times. That means that longer calls occur less frequently than shorter calls. Erlang assumed that blocked calls are immediately cleared and lost and do not return. A formula that Erlang worked out based on these assumptions (Erlang B) is still in use in telephone engineering. See Erlang, Erlang B, Erlang C and Poisson.

Erlang B

A probability distribution developed by A.K. Erlang to estimate the number of telephone trunks needed to carry a given amount of traffic. Erlang B assumes that, when a call arriving at random finds all trunks busy, it vanishes (the blocked calls cleared condition). Erlang B is also known as "Lost Calls Cleared." Erlang B is used when traffic is random and there is no queuing. Calls which cannot get through, go away and do not return. This is the primary assumption behind Erlang B. Erlang B is easier to program than Poisson or Erlang C. This convenience is one of its main recommendations. Using Erlang B will produce a phone network with fewer trunks than one using Poisson formulae. See also Erlang, Erlang A. K., Erlang C, and Traffic Engineering.

Erlang C

A formula for designing telephone traffic handling for PBXs and networks. Used when traffic is random and there is queuing. It assumes that all callers will wait indefinitely to get through. Therefore offered traffic (see ERLANG) cannot be bigger than the number of trunks available (if it is, more traffic will come in than goes out, and queue delay will become infinite). Erlang C is not a perfect traffic engineering formula. There are none that are.

Erlang Formula

A mathematical way of making predictions about randomly arriving work-load (such as telephone calls) based on known information (such as average call duration). Although traditionally used in telephone traffic engineering (to determine the required number of trunks), Erlang formulas have applications in call center staffing as well. See Erlang.


Enterprise Resource Management. Also known as Enterprise Resource Planning (ERP). See ERP for a full definition.


  1. European Radio MEssaging System.

  2. One of the communications protocols used between paging towers and the mobile pagers /receivers/beepers themselves . Other protocols are POCSAG, ERMES, FLEX, GOLAY and REFLEX. The same paging tower equipment can transmit messages one moment in GOLAY and the next moment in ERMES, or any of the other protocols.


  1. Effective Radiated Power.

  2. Enterprise Resource Planning. A concept developed by The Gartner Group to describe the next generation of manufacturing business systems and MRP (Manufacturing Resource Planning) software. ERP software links together back-office computer systems such as manufacturing, financial, human resources, sales force automation, supply-chain management, data warehousing, document management, and after-sales service and support. Such systems typically run on networks of PCs, replacing older mainframe-based systems. ERP software typically makes heavy use of telecommunications. ERP is also known as ERM (Enterprise Resource Management).

Error Burst

A sequence of transmitted signals containing one or more errors but regarded as a unit in error in accordance with a predefined measure. Enough consecutive transmitted bits in error to cause a loss of synchronization between sending and receiving stations and to necessitate resynchronization.

Error Checking And Correction

Error checking is the process of checking a "packet" being transmitted over a network to determine if the package, or the data content within the package, has been damaged. If checked and found wanting, damaged packets are discarded. Error correction is the process of correcting the damage by resending a copy of the original packet. In public frame relay services, the network performs the function of error checking, but not error correction. That function is left to the intelligent end equipment (at the user 's site).

Error Control

Various techniques which check the reliability and accuracy of characters (parity) or blocks of data sent over telecommunications lines. V.42, MNP and HST error control protocols (three common dial-up phone line modem protocols) use error detection (CRC) and retransmission of errored frames (ARQ). See Error Control Protocols.

Error Control Protocols

Besides high-speed modulation protocols, all current models of high-speed dial-up modems also support error control and data compression protocols. There are two standards for error control protocols: MNP-4 and V.42. The Microcom Networking Protocol, MNP, was developed by Microcom. MNP 2 to 4 are error correction protocols. V.42 was established by ITU-T. V.42 actually incorporates two error control schemes. V.42 uses LAP-M (Link Access Procedure for Modems) as the primary scheme and includes MNP-4 as the alternate scheme. V.42 and MNP-4 can provide error-free connections. Modems without error control protocols, such as most 2400 bps Hayes-compatible modems, cannot provide error-free data communications. The noise and other phone line anomalies are beyond the capabilities of any standard modem to deliver error-free data.

V.42 (and MNP 2-4) copes with phone line impairments by filtering out the line noise and automatically retransmitting corrupted data. The filtering process used by V.42 (and MNP 2-4) is similar to the error correction scheme used by file transfer protocols (such as XMODEM). The two modems use a sophisticated algorithm to make sure that the data received match with the data sent. If there is a discrepancy, the data is re-sent.

What is the difference between error control protocols (such as V.42) and file transfer protocols (such as XMODEM)? For one thing, file transfer protocols provide error detection and correction only during file transfers. File transfer protocols do not provide any error control when you are reading e-mail messages or chatting on line. Even though an error control protocol is "on" all the time, we still need file transfer protocols when two modems establish a reliable link. A modem works with bit streams, timing and tones. It does not understand what a file is. When you download or upload a file, your communications software needs to take care of the details related to the file: the filename, file size, etc. This is handled by the file transfer protocol which does more than error-checking.

The other benefit of V.42 (or MNP-4) is that it can improve throughput. Before sending the data to a remote system, a modem with V.42 (or MNP-4) assembles the data into packets and during that process it is able to reduce the size of the data by stripping out the start and stop bits. A character typically takes up 1 start bit, 8 data bits and 1 stop bit for a total of 10 bits. When two modems establish a reliable link using V.42 or MNP-4, the sending modem strips the start and stop bits (which subtracts 20% of the data) and sends the data to the other end. The receiving modem then reinserts the start and stop bits and passes the data to the computer.

Therefore, even without compressing the data you can expect to see as much as 1150 characters per second on a 9600 bps connection. Although the modem subtracts 20% of the data, the speed increase is less than 20% due to the overhead incurred by the error control protocol. This definition, with great thanks to modem expert Patrick Chen.

Error Correcting Code

A code stored on an RFID tag to enable the reader to figure out the value of missing or garbled bits of data. It's needed because a reader might misinterpret some data from the tag and think a Rolex watch is actually a pair of socks. See the next definition.

Error Correcting Mode

A mode of data transmission between the tag and reader in which errors or missing data is automatically corrected.

Error Correcting Protocol

  1. A method of transmitting bit streams in a mathematical way such that the receiving computer verifies to the sending computer that all bits have been received properly. SNA and XMODEM protocols, in the mainframe and microcomputer environments respectively, are Error Correcting Protocols. See Error Control Protocol.

  2. A set of rules used by readers to interpret data correctly from the tag.

Error Correction Code

In computers, rules of code construction that facilitate reconstruction of part or all of a message received with errors.

Error Correction Mode

A method of transmitting and receiving data that eliminates errors.

Error Free Second

A Bellcore (now Telcordia Technologies) definition. An error free second is, surprise, surprise, a one second time interval of digital signal transmission during which no error occurs. That's it.

Error Level

A numeric value set by some programs that you can test with the error- level option of the "If" batch command. It works as follows . Some programs set the DOS errorlevel to a certain number depending on a certain input or response to an event. Let's say when you type the letter "Y" in response to a question the errorlevel is set to 32. Once this is done, you may condition other events based upon this number using an If command in a batch file. You can say "IF ERRORLEVEL = 32 THEN GOTO END." That way, when you type "Y" you will get whatever is at END. This can be very helpful in batch files and other programs for providing "branching" from one event to another based on certain inputs.

Error Logical

An error in the binary content of a signal, for example, bit error.

Error Rate

In data transmission, the ratio of the number of incorrect elements transmitted to the total number of elements transmitted.

Error Suspense

An MCI definition. An automated process which allows billable MCI calls on switch tapes to be processed for billing, while calls with errors are held in the Error Suspense File (a separate file for each switch).

Error Trapping

In software programming, an exception is an interruption to the normal flow of a program. Common exceptions are division-by-zero, stack overflow, disk full errors and I/O (input/output) problems with a file that isn't open. The quality of a software program depends on how completely it checks for possible errors and deals with them. Code used for trapping errors can be excessive. Some programming languages have error trapping built in. Others don't and you have to program it in.


An English word meaning previous. I define this word because I use it in this dictionary and lots of readers have told me they don't know it.


  1. Errored-Second. A count of the number of seconds in which at least one code violation (CV) was detected on a digital circuit. See also Code Violation.

  2. End System: A system where an ATM connection is terminated or initiated. An originating end system initiates the ATM connection, and terminating end system terminates the ATM connection. OAM cells may be generated and received.


End system to Intermediate systems protocol. The OSI protocol used for router detection and address resolution.


IBM Enterprise System/9000: mainframe computer family.


  1. Emergency Stand Alone.

  2. European Space Agency, the international organization that manages all aspects of European joint space programs; headquarters in Paris , France. In Norway. www.esa.int.


The ESC key on the keyboard. Often used to leave (escape) a program. Appears on the upper left of some keyboards on the IBM or compatibles but moves around with IBM's latest keyboard redesign whim. See also ESCAPE.


A formal word for taking your trouble up through the levels of management at the vendor ” until you get your problem resolved. Some users have formal Escalation Charts, which detail action to be taken depending on how many hours the problem persists, etc. Escalation sometimes works and sometimes doesn't, depending on the vendor. Usually it does. The rule in telecommunications (and we guess most other industries) is that "the squeaky wheel gets the most attention." Escalation works well with honey, flowers, plants and chocolates.


  1. The button on many computer keyboards which allows you to "escape" the present program. ESCape is the ASCII control character ” code 27. It is often used to mark the beginning of a series of characters that represent a command rather than data. So called "ESCAPE" because it escapes from the usual meaning of the ASCII code and allows commands to be interspersed in a file of data, especially for data transmission to peripheral devices such as printers and modems. See Escape Sequence.

  2. A means of aborting the task currently in progress.

  3. A code used to force a smart modem back to the command state from the on-line state.

Escape Guard Time

An idle period of time before and after the escape code sent to a smart modem, which distinguishes between data and escapes that are intended as a command to the modem.

Escape Sequence

A series of characters, usually beginning with the escape character, that is to be interpreted as a command, not as data. Escape sequences are used with ANSI.SYS to change the color of a screen. They are mostly used to send print commands to printers. The name Escape is due to the fact that it "escapes" from the usual meaning of the ASCII code, letting characters be commands instead of data, yet interspersed with data in a transmission.


Enterprise Systems CONnectivity. A high-speed fiber optic channel for linking IBM ES/9000 mainframe processors to disk drives and other mainframes. ESCON initially ran at 200 Mbps, but runs at much higher speeds now. ESCON uses the 8B10B signal encoding technique for Clock/Data Recovery (CDR). Competing standards are 10GbE (10 Gigabit Ethernet) and Fibre Channel. See also 8B10B, 10GbE, and Fibre Channel.

Escrow Bucket

A hopper at the outlet of a coin phone's acceptor/rejector that is tipped electrically to return money through the Coin Return or to send the money to the Cash Box as a collection for a completed call.


  1. Electrostatic Discharge. See Electrostatic Discharge.

  2. Electronic Software Delivery. A technique whereby software (both initial installations and upgrades) on computers can be accomplished electronically without the need for floppy disks or CDs. One ESD scenario might be for a bunch of PCs attached to a LAN to be upgraded by a file server on the LAN. Another ESD scenario might be for a single user being able to update his software by downloading upgrades directly from the software vendor via the Internet.

ESD Protection

Electro-Static Discharge Protection. Procedures followed and devices worn by anyone handling manufacturer hardware, in order to protect delicate electronic components from damage due to static electricity. See Electrostatic Discharge.


  1. Enhanced Small Device Interface. An interface which improves the rate of data transfer for hard disk drives and increases the drive's storage capacity.

  2. Nortel Networks term for Enhanced Serial Data Interface.


Extended Super Frame or Extended Superframe Format. A T-1 format that uses the framing bit for non-intrusive signaling and control. A T-1 frame is sent 8,000 times a second, with each frame consisting of a payload of 192 bits, and with each frame preceded by a framing bit. Therefore, there are 8,000 framing bits per second. Previous generations of channel banks (D1, D2, D3, and D4) used the framing bit exclusively for network synchronization purposes. As ESF requires only 2,000 framing bits for synchronization, the remaining 6,000 framing bits can be used for error detection, using cyclic redundancy checking, and data link monitoring and maintenance. As a result, the channel banks need not rob bits from the data payload for such purposes. The ultimate yield is that the payload is not compromised, and the full 1.536 Mbps is available for user data. In a channelized T-1 application, such as traditional PCM-encoded voice, each channel is a reliable 64 Kbps, rather than the 56 Kbps realized through use of older channel banks. While voice is unaffected by the process of bit robbing, data suffers greatly. The impact of intrusive signaling and control is the reason that most carriers limit data communications to 56 Kbps. They have a lot of old channel banks still in use. Note that channel banks must be matched throughout the entire network. In other words, buying an ESF channel bank won't do you any good unless the carrier also has them in place. In networking, as in life in general, the lowest common denominator rules. See also Bit Robbing, Channel, Channel Bank and T-1.


End System Hello packet. Part of CDPD Mobile End System (M-ES) registration sequence.


  1. See Enhanced Serial Interface.

  2. End System Identifier: This identifier distinguishes multiple nodes at the same level in case the lower level peer group is partitioned.


Extended subscriber module.


Expanded Subscriber Module-100A.


Enhanced Specialized Mobile Radio. An enhancement of SMR technology, allowing two-way radio service with the capability to provide wireless voice telephone service to compete against cellular. It uses TDMA technology to put six voice conversations into one 25 kilohertz UHF radio channel in the 806-821 MHz band . ESMR can be deployed on a cellular basis, and supports hand-off, like cellular radio. ESMR was developed by Nextel and Geotek Communications. Nextel acquired a large number of SMR frequencies, applied ESMR technology, and began to offer what is planned to be a nation-wide radio service in direct competition with cellular and PCS. ESMR will support low-speed data, as well as voice, with digital technology yielding both improved efficiency of bandwidth utilization and improved security. The network remains to be fully deployed. See CDMA.


Extended Simple Mail Transport Protocol (see SMTP), described in RFC 1651. Seldom used outside the Unix community.


Expanded Subscriber Carrier Module-100 URBAN.


  1. Emergency Service Number. An ESN is a "list" of emergency numbers that corresponds to a particular ESZ (Emergency Service Zone). This list has to do with 911 service. Usually this ESN list is unique and contains a listing of the corresponding police, fire and ambulance dispatch centers for the caller's area. This "list" is used for selective routing and one button transfer to secondary PSAPs ” Public Safety Answering Positions. The ESN/ESZ concept is especially useful in fringe areas.

  2. Electronic Serial Number. A 32-bit binary number which uniquely identifies each cellular phone. The ESN consists of three parts : the manufacturer code, a reserved area, and a manufacturer-assigned serial number. The ESN, which represents the terminal, is hard- coded, fixed and supposedly cannot be changed. Paired with a MIN (Mobile Identification Number), the ESN and MIN are automatically transmitted to the mobile base station every time a cellular call is placed. The Mobile Telephone Switching office checks the ESN/MIN to make sure the pair are valid, that the phone has not been reported stolen, that the user's monthly bill has been paid, etc., before permitting the call to go through. At least that's the theory. It doesn't always work this way on calls made from roaming cellular phones. And some cellular phones have been known to have their ESNs tampered with (it's called fraud) which tends to mess up the billing mechanisms. See also EESN and MIN.

  3. Electronic Switched Network.


Equipment Superior to Operator. When closing help desk tickets, it describes situations where the problem was user stupidity, such as the power cord not plugged in, the monitor unplugged, the keyboard not attached, etc. Also called SUT, for Stupid User Tricks.


European Standardization Organizations.


  1. Enhanced Serial Port. The Hayes Enhanced Serial Port (ESP) adapter, introduced in late 1990, replaces and extends the traditional COM1/COM2 serial port adapter. The ESP combines dual 16550 UARTS with an on-board communications coprocessor. The ESP has two distinct modes of operation to provide both old and new standards in the same package: Compatibility Mode and Enhanced Mode. Each ESP port can be independently operated in either mode. Default modes are configured via DIP switches and can be modified by ESP commands. The MCA-bus version of the ESP uses Programmable Option Selection (POS) rather than DIP switches. See Enhanced Serial Interface.

  2. Enhanced Service Provider ” a vendor who adds value to telephone lines using his own software and hardware. Also called an IP, or Information Provider. An example of an ESP is a public voice mail box provider or a database provider, say one giving the latest airline fares. An ESP is an American term, unknown in Europe, where they're most called VANs, or Value Added Networks. See also Open Network Architecture and Information Provider.

  3. Ethernet Service Provider.

  4. EncapSulated Postscript File.

  5. Encapsulating Security Payload. The portion of the IPSec virtual private networking protocol which is used predominantly to provide data privacy.


European Selective Paging Association.


European Strategic Program for Research and development in Information Technology. A $1.7 billion research and development program funded by the European Community.


End System Query packet. Part of CDPD Mobile End System (M-ES) registration procedures.


  1. Electronic Switching System. ESS was originally a designation for the switching equipment in Bell System central offices but has slightly more general use now. In the independent telephone company industry, the abbreviation for the same thing is EAX. The first 1ESS switch went into service in May 1965 in Succasunna, New Jersey.

  2. European Standardization System.

ESS No 4

AT&T's large toll telephone switch. It will handle over 100,000 trunks and over 500,000 attempts at making a call each hour. It's large and sophisticated and can probably be configured to be the largest telephone switch in the world.

ESS No 5

AT&T's Class 5 digital central office. See also End Office.

Essential Lines

A telephone company definition. In order to guarantee to certain customers the ability to make outgoing calls during an emergency, the telephone company's Customer Services Department designates these customers as "essential." Examples of essential lines are:. police and fire departments, ambulance companies, hospitals , etc. Whenever Line Load Control is activated, outgoing service may be selectively denied to nonessential customers in order to preserve originating calling capacity for those customers having a documented priority. Also see - Class A lines.

Essential Service

  1. A service provided by a telecommunications provider, such as an operating telephone company or a carrier, for delivery of priority dial tone. Generally , only up to 10 percent of the customers may request this type of service. See Essential Lines.

  2. A service that is recommended for use in conjunction with NS/EP (national emergency) telecommunications services.


ESSX (pronounced essex) is some local phone companies' name for Centrex. See Centrex.

Established Connection

A telephone company term. A connection on which all necessary switching or operating steps have been taken to connect the calling and called lines. Generally speaking, it is somewhat broader than the term "completed call," in that it includes established connections to tones or announcements, as well as completed calls. A completed call is a connection between two telephones.


Emergency Service Zone. This term is used in conjunction with 911 emergency service. An ESZ is a geographic area that is served by a unique mix of emergency services. Each ESZ has a corresponding ESN (a list of Emergency Service Numbers) which enables 911 service to properly route incoming calls.


Exchange Termination. Refers to the central office link with the ISDN user.


Extended TACS. The cellular technology used in the United Kingdom and other countries. It is developed from the U.S. AMPS technology. See also AMPS, TACS, NTACS and NAMPS.


A retailer who conducts his business by electronic commerce ” i.e. over the Internet and the world wide web.


Abbreviation for end-of-transmission block. The binary code is 0111001, the hex is 71.


Enhanced Throughput Cellular is an error correction cellular communications protocol, which helps prevent disruptive signal fading and thus reduces the number of dropped calls.


Antiglare treatment that prevents glare but also reduces screen sharpness and clarity on monitors . Generally considered an obsolete technology.

Eternity Hold

My own creation for what happens when an unthinking corporation has a machine which answers your phone call and then says something like "All our agents are currently busy. Our customers (i.e. you) are important to us. (Some actually mean it.) And we'll connect you with the next available agent." And then they leave you waiting forever ” or an eternity. Governmental agencies, airlines and police departments (especially when you need them) tend to be firm believers in placing their callers on Eternity Hold. A new enhancement to Eternity Hold is Conference Hold. Here everyone on Eternity Hold can speak to everyone else on hold. You can imagine the conversation. "Let's all talk about why we hate this airline..." I made this service up. It doesn't exist, but I love the idea. Imagine the conversations....


An undefined path. See Ethernet and Luminiferous Ether.

Ethical Hacking

A means for identifying vulnerabilities by having an authorized individual(s) attempt to break into a computer system or network and report their findings to the people who own and/or run the computer system or network.

Ethical Lapse



ELEC). Ethernet Local Exchange Carrier. Facilities-based service providers employing Optical Ethernet technology. They typically build metro Ethernet networks by leasing dark fiber and installing Optical Ethernet equipment in metro POPs and collocation centers. The "EtherLEC" business model is straightforward: provide low-cost Internet access, metro network and WAN services based on "native Ethernet." Subscribers benefit from a lower cost of ownership combined with lower transport costs than traditional TDM-based private lines.


ADC Telecommunications' name for a "revolutionary new idea allowing transport of native mode Ethernet and Fast Ethernet (100 million bits per second) data packets over a wide area network (WAN). Unlike typical Ethernet transport solutions," according to ADC Telecommunications (www.adc.com), "EtherRing has no distance limitations."


A Local Area Network (LAN) standard officially known as IEEE 802.3 (1980)/ Ethernet, and other LAN technologies are used for connecting computers, printers, workstations, terminals, servers, etc., within the same building or campus. Ethernet operates over twisted wire and over coaxial cable at speeds beginning at 10 Mbps. For LAN interconnection, Ethernet is a physical link and data link protocol reflecting the two lowest layers of the OSI Reference Model. The theoretical limit of 10-Mbps Ethernet, measured in the smallest 64-byte packets, is 14,800 pps (packets per second). By comparison, Token Ring is 30,000 and FDDI is 170,000.

Ethernet specifies a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) MAC (Media Access Control) mechanism. CSMA/CD is a technique of sharing a common medium (e.g., twisted pair, or coaxial cable) among several devices. As Byte Magazine explained in its January, 1991 issue, Ethernet is based on the same etiquette that makes for a polite conversation: "Listen before talking." Of course, even when people are trying not to interrupt each other, there are those embarrassing moments when two people accidentally start talking at the same time. This is essentially what happens in Ethernet networks, where such a situation is called a "collision." If a node on the network detects a collision, it alerts the other nodes by jamming the network with a collision "notification." Then, after a random pause, the sending nodes try again. The messages are called frames (see the diagram).



Destination address

Source address


Data up to 1500

Frame check sequence

8 bytes

6 bytes

6 bytes

2 bytes


4 bytes (containsCRC

The first personal computer Ethernet LAN adapter was shipped by 3Com on September 29, 1982 using the first Ethernet silicon chip from SEEQ Technology. Bob Metcalfe created the original Ethernet specification at Xerox PARC and later went on to found 3Com. In the October 31, 1994 issue of the magazine InfoWorld, Bob Metcalfe explained that Ethernet got its name "when I was writing a memo at the Xerox Palo Alto Research Center on May 22, 1973. Until then I had been calling our proposed multimegabit LAN the Alto Aloha Network. The purpose of the Alto Aloha Network was to connect experimental personal computers called Altos. And it used randomized retransmission ideas from the University of Hawaii's Aloha System packet radio network, circa 1970. The word ether came from luminiferous ether ” the omnipresent passive medium once theorized to carry electromagnetic waves through space, in particular light from the Sun to the Earth. Around the time of Einstein's Theory of Relativity, the light- bearing ether was proven not to exist. So, in naming our LAN's omnipresent passive medium, then a coaxial cable, which would propagate electromagnetic waves, namely data packets, I chose to recycle ether. Hence, Ethernet."

According to Metcalfe, "Ethernet has been renamed repeatedly since 1973. In 1976, when Xerox began turning Ethernet into a product at 20 million bits per second (Mbps), we called it The Xerox Wire. When Digital, Intel, and Xerox decided in 1979 to make it a LAN standard at 10 Mbps, they went back to Ethernet. IEEE tried calling its Ethernet standard 802.3 CSMA/CD ” carrier sense multiple access with collision detection. And as the 802.3 standard evolved, it picked up such names as Thick Ethernet (IEEE 10Base-5), Thin Ethernet (10Base-2), Twisted Ethernet (10Base-T), and now Fast Ethernet (100Base-T)."

Ethernet PC cards now come in a couple of basic varieties ” for connecting to an Ethernet LAN via coaxial cable or via two twisted pairs of phone wires, called 10Base-T. See also 10Base-T, Collision Domain, Ethernet Controller, Ethernet Identification Number, Ethernet Switch, Ethertalk, Frame, Gigabit Ethernet, Luminiferous Ether, Thinnet and Token Ring.

The May 22, 2003 issue of my favorite magazine, the Economist, had an article on Ethernet. I excerpt it because it's so good: "WHEN Ethernet, now by far the most popular way of distributing data around local networks, was devised by Bob Metcalfe in a memo on May 22, 1973, at Xerox's celebrated Palo Alto Research Centre (PARC), it was designed to send data at about three megabits per second. Today, one gigabit per second Ethernet is common and speeds of 100 gigabits per second are being developed. The vast majority of the Internet's traffic begins and ends its journey on Ethernet networks, which are found in nearly every office network and home broadband connection. It was not supposed to be this way. Few imagined that this particular networking protocol would last as long as it has. Indeed, the landscape is littered with better-financed, better- backed rival protocols that failed against Ethernet. IBM's Token Ring system is one famous casualty . Asynchronous Transfer Mode, supported by the telephone industry, is another. So the case of Ethernet is worth examining: the reasons for its longevity may offer lessons to the information-technology industry. Keep it simple, stupid. The first reason is simplicity. Ethernet never presupposed what sort of medium the data would travel over, be it coaxial cable or radio waves (hence the term "ether" to describe some undefined path). That made it flexible, able to incorporate improvements without challenging its fundamental design.

Second, it rapidly became an open standard at a time when most data-networking protocols were proprietary. That openness has made for a better business model. It enabled a horde of engineers from around the world to improve the technology as they competed to build inter-operable products. That competition lowered the price. What is more, the open standard meant that engineers in different organisations had to agree with each other on revised specifications, in order to avoid being cut out of the game. This ensured that the technology never became too complex or over-designed. As Charles Spurgeon, author of "Ethernet: The Definitive Guide" puts it, "It always stayed close to the ground. It addressed problems customers came up against, not problems that networking specialists thought needed to be addressed." That, coupled with the economies of scale that come from being the entrenched technology, meant that Ethernet was faster, less expensive and less complicated to deploy than rival systems.

Third, Ethernet is based on decentralisation. It lets smart "end-devices", such as PCs, do the work of plucking the data out of the ether, rather than relying on a central unit to control the way those data are routed. In this way, Ethernet evolved in tandem with improvements in computing power-a factor that was largely overlooked by both critics and proponents when Ethernet was being pooh-poohed in the 1980s and early 1990s.

Beyond the technology, there is even a lesson for companies investing in research, albeit one learned through tears rather than triumph. Xerox failed to commercialise Ethernet, as it similarly missed exploiting other inventions created at PARC, such as the mouse and the graphical user interface. To develop Ethernet fully, Dr Metcalfe had to leave PARC and found 3Com, now a big telecommunications-component firm. The lesson may have sunk in. In January 2002 PARC was carved out as an independent subsidiary of Xerox. That allows it to explore partnerships, spin-offs and licensing agreements without having to get its parent's permission.

And the future? Many geeks believe the fashionable wireless standard 802.11b, better known as Wi-Fi, is poised to become the next iteration of the technology, once concerns about its security have been resolved. Wi-Fi is able to deliver cheap internet access at a rate of many megabits-per-second, and it can do so at a range of up to 100 metres. Dr Metcalfe, who based Ethernet's early designs on a radio network called AlohaNet, that linked the Hawaiian islands, sees Wi-Fi as "Ethernet coming home".

That raises the question of whether a technology that outlived even its inventor 's expectations will ever be supplanted, or whether it will continue to be upgraded indefinitely. As Dr Metcalfe quips, "When something rises up to defeat Ethernet, it's very likely that they're going to call it Ethernet." Now that, indeed, is adaptability.

Ethernet Address

The address assigned to a network interface card by the original manufacturer or by the network administrator if the card is configurable. This address identifies the local device address to the rest of the network and allows messages to reach the correct destination. Also known as the media access control (MAC) or hardware address.

Ethernet Controller

The unit that connects a device to the Ethernet cable. An Ethernet controller typically consists of part of the physical layer and much or all of the data link layer and the appropriate electronics.

Ethernet Extender

Normal Ethernet ” the kind you have in your office ” only works a few hundred feet. But Ethernet extenders literally extend that several miles. For example, one extended whose specifications I'm looking at shows it can achieve 16 Mbps over two km, 4.6 Mbps over 3 km, 2.3 Mbps over 5 Km and 128 Kbps over 8 Km. you can place an extender on


Get shut out. No hits. No runs. NO errors.

Ethernet Identification Number

This is a unique, hexadecimal Ethernet number that identifies a device, such as a PC/AT with a SpeedLink/PC16 network interface card installed, on an Ethernet network.

Ethernet II (DIX)

Defined by Digital, Intel and Xerox. The frame format for Ethernet II differs from that of IEEE 802.3 in that the header specifies a packet type instead of the packet length.

Ethernet Meltdown

An event that causes saturation on an Ethernet-based system, often the result of illegal or misdirected packets. An Ethernet meltdown usually lasts for only a short period of time.

Ethernet Packet

A variable-length unit in which information is transmitted on an Ethernet network. An Ethernet packet consists of a synchronization preamble, a destination address, a source address, a field that contains a type code indicator, a data field that can vary from 46 to 1500 bytes, and a cyclical redundancy check (CRC) that provides a statistically derived value used to confirm the accuracy of the data.

Ethernet Switch

Ethernet is the most common local area network (LAN) standard in the world today. Ethernet is very cheap, but its approach to congestion management is on the ugly side. There is a solution and it's called an Ethernet Switch. Here's an explanation: In typical Ethernet LAN, transmission is over a shared bus. When an Ethernet-attached device (e.g. a PC) puts information onto the network (called data frames or data packets), those frames move in both directions, and pass by all devices on the network. Every attached workstation, printer and host sees all the information on the Ethernet LAN. At some point, a device will see data that's intended for it. It will recognize the address in the data frame, as it passes by, and take that information off the network. But, since every bit of information must pass by every device, Ethernet networks can become very heavily congested very quickly. While the theoretical 10Base-T Ethernet data rate is 10Mbps (ten million bits per second), they often effectively run at a fraction of that speed ” as slow as 500,000 bits per second. One way of reducing Ethernet congestion is through the use of hubs. Hubs allow the Ethernet to be divided into physical segments at the workgroup level, with each workgroup representing a "community of interest." This segmentation process serves to reduce congestion by confining traffic to all those Ethernet stations on the shared hub, passing it on to other hubs only if necessary. In other words, the single logical LAN is subdivided into multiple physical and logical segments. However, the hub still presents the data to all connected devices over a common, shared bus. Thus, hubs really don't do anything internally to control congestion. A much better, but more expensive solution is something called an Ethernet Switch. What it is does is simple. It breaks out the stuff for each device and sends it directly to and from only that device. It's wired directly to each device. Think phone system. You get the idea. Let's consider an Ethernet switch at the workgroup- level. Workgroup-level switches serve a community of interest, such as the marketing department or the accounting department. An Ethernet workgroup switch is used to interconnect Ethernet-attached devices (e.g., workstations, printers, and servers), each of which connects to a port on the switch via UTP (Unshielded Twisted Pair). When the transmitting workstation, for instance, sends an Ethernet frame of data to the switch, that frame is captured in a buffer and is fragmented into smaller data units. The switch then flows those fragments over a common, shared bus inside the switch, from the input port of the originating device to the output port associated with the destination device. The common bus also can support other transmissions, as it is carved into time slots through a process akin to TDM (Time Division Multiplexing). More complex workgroup-level switches may involve a switching matrix comprising multiple, interconnected busses , and yielding multiple possible transmission paths between ports. In either case, the switch directs the data only to the target device, rather than to all attached devices. Therefore, and unlike hubs, switches do a lot to reduce Ethernet LAN congestion. What this means to you is that a 36-port Ethernet switch can allow you and all 35 of your co-workers to communicate simultaneously . You can all pass data between each other at the same time, or you can all access the same e- mail server at the same time. Depending on the nature, design and quality of the internal switching matrix, you each may get 10Mbps or more (switches come in 100 megs also). Your traffic will be confined to your own workgroup unless it needs to go somewhere else. Workgroup switches can be interconnected directly. For example, the accounting department might have its own switch on the 10th floor, and the sales and marketing department might have its own switch on the first floor. Connecting from switch to switch, the top salesman can check his commission statement, assuming that the accounting department allows him access to that database (highly unlikely ). Again, the data remain confined to your workgroup switch unless they need to go elsewhere. Workgroup switches also can be interconnected through either a backbone switch or a router, which is a highly intelligent (read much more capable, but much slower and much more expensive) switch. In either case, the data are forwarded from one workgroup switch to another only if the destination address requires. A backbone switch has a higher-speed internal switching matrix, and connects to workgroup-level hubs and switches through high-speed links, commonly in the form of fiber optics. Backbone switches also can be connected to other backbone switches. Again, the data go only where they need to go, rather than being blasted all over the company, and slowing down the whole network in the process. See also Ethernet, Gigabit Ethernet, Hub, Router and Switch.

Ethernet Transceiver

A device used in an Ethernet local area network that couples data terminal equipment to other transmission media.


An Ethernet protocol used by Apple computers. AppleTalk protocol governing Ethernet local area network transmissions. Also the Apple Computer Ethernet adapter and drivers. Apple's implementation of Ethernet is compliant with IEEE specification 802.3.


A two-byte code indicating protocol type in an Ethernet local area network packet.


Electronic Telephone Interface.


Emirates Telecommunications Corporation is the sole provider of telecommunications services throughout the United Arab Emirates. The head office is in Abu Dhabi.


Electronic Ticketing Machine. A machine that looks like a banking Automated Teller Machine (ATM), except that it will dispense airline tickets and possibly, hotel reservations , car rental agreements, etc.


  1. Electronic Tandem Network. An ETN is a large private network which comprises dedicated leased lines interconnecting electronic tandem switches. ETNs were deployed in the 1970s and 1980s by very large user organizations such as state and federal governments .

  2. Earning Telephone Number. A billing term which is synonymous with WTN (Working Telephone Number). Multiple ETNs can be associated with a single BTN (Billing Telephone Number).


The European Public Telecommunications Network Operations Association (ETNO).


enhanced Telecom Operations Map. See Telecom Operations Map.


  1. Estimated Time to Repair. "The DSL line is down. The ETR is two hours."

  2. ETSI (European Telecommunications Standards Institute) Technical Report. See also ETSI.


  1. ETSI (European Telecommunications Standards Institute) Technical Specification. A standard defined by the European Telecommunications Standards Institute (ETSI). See also ETSI.

  2. Electronic Tandem Switching. See Electronic Tandem Switching.

  3. Ethernet Terminal Server. A cost-effective and flexible way of connecting serial-based asynchronous terminals and peripherals to one or more host computers across an Ethernet LAN. See Terminal Server.

ETS 300 211

Metropolitan Area Network (MAN) Principles and Architecture.

ERS 300 212

Metropolitan Area Network (MAN) Media Access Control Layer and Physical Layer Specification.

ETS 300 217

Connectionless Broadband Data Service (CBDS).


A Nortel Networks term for an electronic Telephone Set.


European Telecommunications Standards Institute, is the European counterpart to ANSI, the American National Standards Institute. ETSI is based in Sophia-Antipolis, near Nice, France. ETSI's task is to pave the way for telecommunications integration in the European community as part of the single European market program. ETSI was founded in 1988 as a result of an in initiative of the European Commission. It was established to produce telecommunications standards by democratic means, for users, manufacturers, suppliers, administrations, and PTTs. ETSI's main aim is the unrestricted communication between all the member states by the provision of essential European standards. It is now an independent, self-funding organization, which works closely with both CEPT (European Conference of Posts and Telecommunications Administrations ) and EBU (European Broadcasting Union).

ETSI also works closely with CENELEC, which is responsible for electrotechnical standards, and CEN, which is responsible for European standardization in all remaining fields. Certified products are awarded the CE Mark, signifying that a company has met the applicable essential health and safety requirements and the specific conformity assessment requirements to market its product in the European Union under the "New Approach" directives. www.etsi.org. See also ANSI, CE Mark, CEN, CENELEC, CEPT, and EBU.


European Telecommunications Standards Institute's open standard interface between an Access Node (AN) and a Local Exchange (LE) for supporting PSTN (Public Switched Telephone Network) and ISDN (Integrated Services Digital Network). Examples of Access Nodes include Digital Loop Carrier (DLC) systems, wireless loop carrier system, and Hybrid Fiber Coax (HFC) systems.


End of Text. Indicates the end of a message. If multiple transmission blocks are contained in a message in Bisynch systems, ETX terminates the last block of the message. ETB is used to terminate preceding blocks. The block check character is sent immediately following ETX. ETX requires a reply indicating the receiving station's status. The binary code is 0011000, the hex is 30. See Packet.


EUC stands for Extended Unix Code. It is a standard way of representing extended character sets such as Japanese.


End User Common Line charge. A FCC tariff term defined in FCC Rules 69.104 as follows: "A charge that is expressed in dollars and cents per line per month shall be assessed upon end users that subscribe to local exchange telephone service, Centrex or semi-public coin telephone service to the extent they do not pay carrier common line charges. Such charge EUCL shall be assessed for each line between the premises of an end user and a Class 5 office that is or may be used for local exchange service transmissions. Each Single Line Service is charged one CALC or EUCL. The amount varies by state." The intent is that the EUCL, in combination with the CCL (Carrier Common Line Charge) compensate the LEC for the use of the local loop for the purposes of originating/terminating interLATA long distance calls. The LEC receives no direct benefit from such traffic, although its investment in, and maintenance cost associated with, the local loop is considerable. The EUCL is known variously as the Access Charge, CALC, and SLC. See also Access Charge and CCL.


An electronic mail sending and receiving software program that runs on Macs and under Windows and is probably the most common e-mail service used by people on the Internet. It is manufactured and distributed by Qualcomm Enterprises, San Diego, California. Eudora Pro is the commercial version (i.e. the one that costs money). It includes features that are not in Eudora Light, the freeware version and one in heaviest use on the Internet.


Extended Unique Identifier-48 (bits). The IEEE (Institute of Electrical and Electronics Engineers) administers the addressing scheme for all LANs (Local Area Networks) adhering to the Project 802 standards, including 802.3 Ethernet and 802.5 Token Ring. The addressing scheme comprises a Company ID and an Extension ID, each of 24 bits. The Company ID, which is administered directly by the IEEE RAC (Registration Authority Committee), identifies the manufacturer of the NIC (Network Interface Card) or other interface hardware. The Extension ID, also known informally as the Board ID, is assigned by the manufacturer. Theoretically, the EUI-48 address is unique, although duplications occasionally are reported, most likely due to manufacturing errors. The EUI-48 comprises what we normally refer to as the MAC (Medium Access Control) address. The IEEE refers to it as the Equipment Identifier, as the 48-bit address effectively is a serial number that identifies the manufacturer of the hardware, the manufacturing run, etc. It generally resides in ROM (Read-Only Memory) on the NIC. See also EUI-64 and MAC Address.


Extended Unique Identifier-64 (bits). The IEEE expanded the 48-bit EUI-48 addressing scheme for LANs to a 64-bit global identifier known as EUI-64. This Equipment Identifier is what we normally think of as a MAC (Medium Access Control) address. It a concatenation of the 24-bit Company ID assigned by the IEEE RAC (Registration Authority Committee), and an expanded 40-bit Extension Identifier assigned by the organization with that Company ID assignment, i.e., the manufacturer of the NIC (Network Interface Card). This 40-bit Extension Identifier replaces the 24-bit EI used in the predecessor EUI-48. This new scheme increases the available number of unique addresses, which typically are hard- coded in ROM (Read-Only Memory) on a chipset in a NIC. Thereby, more devices can have globally unique addresses ” about 1 trillion per manufacturer. The move to EUI-64 is not entirely due to the increasing popularity of LANs, at least not traditional LANs. Rather, it is due to the increasing popularity of the both Internet and the IP (Internet Protocol) protocol. IPv6 (IP version 6), which ultimately will replace the current IPv4, addresses often include an Interface ID field, which is defined according to the EUI-64 format. Ultimately, you might be running the IPv6 protocol on your LAN-attached workstation, and essentially have a single address that you would use for seamless access to both the LAN-attached resources and to the public Internet. You really wouldn't want that (due to security, privacy, and other concerns), but you certainly could. In any event, the 40-bit EI address would be the same length across both the LAN and the IPv6 Internet, which makes necessary address translations a lot easier. See also EUI-48, IPv6, and MAC Address.


End-User License Agreement. An agreement between you, the user, and the company which allows you to use its software. See Disclaimer.


European UNIX Network. (Original name). Now a major European Internet Service provider.


Another way of writing Euro, the European currency. Since Euro.


EUropean institute for REsearch and Strategic studies in TeleCOMmunication.


New European single currency introduced on January 1, 1999 by 11 European countries, who agreed to lock their exchange rates to the euro, which was, at the time of its birth, worth around $1.17. But is no longer.


See Euro-ISDN.


European ISDN defined by European Telecommunications Standards Institude (ETSI). Also known as NET5.2 and V5.2. It differs from North American National ISDN-1 in that Euro-ISDN is very limited in the options it offers. In the United States, ISDN comes with many options, including two call appearances , conference calling, call forwarding variable, call forwarding ” busy, call forwarding ” no answer, voice mail with indicator, two secondary directory numbers, etc. That makes North American ISDN more full-featured , but much less easy to order. Users, can however, call from the United States to Europe and complete ISDN calls. They can not carry their end-user ISDN equipment from the United States and use it in most places in Europe. Other subtle differences between Euro ISDN and its North American counterpart. Euro ISDN does not require the user to send a channel ID information element, giving network side full control of channel selection and eliminating glare. Channels are always enabled. Overlap dialing is allowed in the user to network direction, eliminating outbound number configuration on the user side. Provides a sending complete information element that indicates the called number is complete or there is no called number. Does not allow NFAS (non-facility associated signaling) and hence eliminates the need for backup D-channel signaling. Euro ISDN sends calling name using the Display IE whereas North American NI-2 did not support calling name and NI-3 uses the Facility IE.


European Association of Business Machines Manufacturers and Information Technology Industry.


See Digital Video Broadcast.

European Article Numbering

EAN. The bar code standard used throughout Europe, Asia and South America. It is administered by EAN International.

European Commission

The administrative body of the European Union, and a central source of policy, legislation and funding for pan-European research and development in ICT applications.

European Competitive Telecommunications Association See


European Computer Manufacturers Association


European Digital Signaling System no. 1.

EDSS1. The European variant of the SS7 (Signaling System 7) signaling and control protocol for use over the ISDN D (Delta) channel. EDSSI was developed by ETSI (European Telecommunications Standards Institute). See also ETSI, ISDN, and SS7.

European Space Agency

The European equivalent of the U.S.'s NASA ” National Aeronautics and Space Administration.


International ISDN pilot project for travel agents.


EUROpean TELecommunications DEVelopment. An organization involved in telecommunications standardization.


EUropean TELecommunications SATellite organization. Inter-governmental organization that aims to provide and operate a communications satellite for public intra- European international telecommunications services. The segment is also used to meet domestic needs by offering leased capacity, primarily for television. U.K. and France are the largest shareholders, with about 25 member countries in total.


Enhanced Unshielded Twisted Pair. UTP Cables that have enhanced transmission characteristics. Cables that fall under this classification include Category 4 and above.


European Videotelephony.


See EvDO below.


Busy Line Transfer.


Economic Value Added. A financial measure of whether you're making more money with your plant, factory, assets, etc. in your present business than you would be if you sold everything and stuck the proceeds in a investment. The common assumption is that you can get a 10% or 11% return. If you earn more than that, you're EVA positive. EVA is a term you hear a lot around AT&T. You can become EVA positive in any ways ” writing down the value of your capital is one way. Sacking people works too. And, so does selling more (presumably, at a decent price).

Evanescent Wave

Light guided in the inner part of an optical fiber's cladding rather than in the core .


EvDO (Evolution Data Only) is a new wireless telecommunications technology that provides wireless data connections that are 300,000 to 600,000 bits per second ” as much as 10 times as fast as a regular dial-up modem. Proponents say EvDO offers huge advantages over WiFi. EvDO can work over existing cell phone networks. One of the biggest barriers to EvDO is that it requires wireless companies to set aside a slice of their valuable airwaves just to transmit data. Because mobile phone companies barely have enough room to handle their voice traffic, EvDO is likely to remain on the back burner until the firms can acquire more spectrum. EvDO is a CDMA 2000 technology. EvDO is also spelled Ev-DO and EV-DO.

Even Parity

In data communications there's something called a Parity Bit that's used for error checking. The transmitting device adds that parity bit to a data word to make the sum of all the "1" ("one" bits) either odd or even. If the sum is odd, the result is called ODD parity. If it's even, it's called EVEN PARITY. See also Parity.


An unsolicited communication from a hardware device to a computer operating system, application, or driver. Events are generally attention-getting messages, allowing a process to know when a task is complete or when an external event occurs.

Event Code

A code that an agent in a call center enters at the conclusion of a call. Event codes can trigger a variety of follow-up activities such as an acknowledgement letter, or inclusion in a list for a subsequent campaign.

Event Driven

A style of programming under which programs wait for messages to be sent to them and react to those messages. See Event Driven Alarms/Triggers/Ticklers.

Event Driven Alarms/Triggers/Ticklers

In a parallel process, an event trigger can be set to move the processing forward when a set of criteria is met (ex. the last piece of documentation is added to the file). Alarms can also be time-driven, as when a folder is automatically routed to exception processing if no action is taken within a specified time frame. This term is often found in workflow management.

Event History

A history of the activities that have been carried out on a record, (customer or prospect). For example, phone calls and mailers, offers and so on.

Event Mask

The set of events that the SLEE (Service Logic Execution Environment) designates the ASC (AIN Switch Capabilities) to report for a particular connection segment, and an indication for each event if the ASC should suspend processing events for that connection segment until the SLEE sends a message back. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.

Event Message

A message provided by the switching domain to the computing domain to indicate one of the following:

  1. A change in the state of a telephone call by reporting state transitions of each connection in the call (Call Control Events);

  2. A physical or logical device change that has taken place (such as Do Not Disturb being set or a device's microphone being muted) at a device physical and Logical Device Feature Events);

  3. A change in call-associated information (Call Associated Feature Events);

  4. A change in switching domain specific information that is associated either a device or call (Private Data / Information Events). See Call-Progress Event Message.

Event Report

Synonymous with Event Message.

Event Signaling

All telephone switches use the same three general types of signals:

  • Event Signaling initiates an event, such as ringing.

  • Call Progress Signaling denotes the progress (or state) of a call, such as a busy tone, a ringback tone, or an error tone.

  • Data Packet Signaling communicates certain information about a call, for example, the identify of the calling extension, or the identity of the extension being called.


When choosing between two evils I always like to take the one I've never tried before ” Mae West.


Call forwarding, busy line.


Enhanced Variable Rate Vocoder. A vocoder (voice coder ) used in CDMA (Code Division Multiple Access) cellular systems. EVRC digitizes and compresses analog voice signals through an EVRC DSP (Digital Signal Processor), improving CDMA bandwidth utilization and, therefore, enhancing system capacity by supporting voice transmission at a rate of approximately 8 Kbps. This bit rate is comparable to that of 13-Kbps QCELP (Qualcomm Code Excited Linear Prediction) which can run at either 13 Kbps or 8 Kbps. It is a significant improvement over the 64 Kbps required to support toll-quality voice in the wireline PSTN (Public Switched Telephone Network). See also QCELP.


A specific size of rigid waveguide with an elliptical cross sectional shape.


Electronic Warfare . The military use of radar, electronic counter measures and electronic counter-counter measures to keep an enemy from finding invading forces, on land or in the air. It covers such methods as sending out planes equipped with equipment which transmit thousands of signals purporting to be signals that an enemy radar might see on locating an incoming plane. By sending thousands of such signals, the enemy's radar becomes a myriad of "radar" signals, of bright spots. Thus it's impossible for the enemy to read any intelligent information. There are also anti-radiation missiles which home in on and destroy air-defense radar facilities. The only defense against such anti-radiation missiles is to turn off the radar. Electronic warfare also covers such techniques as jamming radio frequencies, anti-jamming.


European Workshop for Open Systems.


Electronic White Pages.


Generic name for digital central office switches from Siemens. EWSD actually stands for Elektronisches WahlSystem Digital. In German, the common meaning of wahlen is to select, as in "I'll select blue for the new color for my house." In the phone business, it was a simple jump to selecting a phone number, to its present meaning today ” to dial. So if you translate EWSD into English, it really means electronic digital dialing system. You figure.

Ex Parte Presentation

A Federal Communications Commission definition. Any communication addressing the merits or outcome of a particular proceeding made to decision-making personnel (or in some proceedings , from the decision-making personnel), which, (1) if written, is not served on the parties to the proceeding, or (2) if oral, is made without opportunity for the parties to the proceeding to be present. A simpler defintion: Ex parte refers to statements, meetings or filings that are made outside of an official comment-and-replay period. They must be reported and a summary of them made available in the public record.


EB. A combination of the Greek "hex," meaning "six," and the English "bite," meaning "a small amount of food." A unit of measurement for physical data storage on some form of storage device ” hard disk, optical disk, RAM memory etc. and equal to two raised to the 60th power, i.e. 1,152,921,504,606,800,000 bytes.

KB = Kilobyte (2 to the 10th power)

MB = Megabyte (2 to the 20th power)

GB = Gigabyte (2 to the 30th power)

TB = Terabyte (2 to the 40th power)

PB = Petabyte (2 to the 50th power)

EB = Exabyte (2 to the 60th power)

ZB = Zettabyte (2 to the 70th power)

YB = Yottabyte (2 to the 80th power)

One googolbyte equals 2 to the 100th power.

Exalted Carrier Reception

A method of receiving either amplitude- or phase- modulated signals in which the carrier is separated from the sidebands, filtered and amplified, and then combined with the sidebands again at a higher level prior to demodulation.


Exchangeable Card Architecture. ExCA is a hardware and software architectural implementation of PCMCIA 2.0 from Intel that allows card interoperability and exchangeability from system to system, regardless of manufacturer. See PCMCIA.


  1. In telecom, when something happens that's "unusual," it's an exception. The key is to define what's "unusual." For example, you might define that every phone call of longer than 15 minutes is an "exception." Now you have defined an "exception," the question is how to use that information. You might ask the phone system to print out each "exception" call on a printer next to your desk immediately after the call is over. Or you might ask the machine to print "Exceptions" reports at the end of the month listing all the calls over 15 minutes. These reports might be by perpetrator. Or in chronological order, or order of phone number called, etc. In short, any event you define by certain strict parameters can be an "exception." Management reports printed in full are almost useless because they contain so much information, so much paper. Management reports which list only previously-defined "exceptions" are more useful. They show you where to focus your attention so as to improve your or your company's performance.

  2. In software programming, an exception is an interruption to the normal flow of a program. Common exceptions are division-by-zero, stack overflow, disk full errors and I/O (input/output) problems with a file that isn't open. The quality of a software program depends on how completely it checks for possible errors and deals with them. Code used for trapping errors can be excessive. Some programming languages have error trapping built in. Others don't and you have to program it in.

Exception Condition

In data transmission, the condition assumed by a device when it receives a command that it cannot execute.

Exception Reports

Reports generated by "exceptions," often detailing extra long calls or indications of bad circuits. See Exception.

Excess Burst Size

Be, or Burst excess. A Frame Relay term defining the maximum data rate that your carrier network will attempt to transport over a specified period of time, known as the Time Interval, known as Tc (Time committed). Any data rate above the CIR (Committed Information Rate) is above the commitment between the carrier and you, the user organization. Excess data frames, therefore, may be marked as DE (Discard Eligible). See also Committed Burst Size, and Committed Information Rate, Discard Eligible, Measurement Interval, and Time Interval.

Excess Insertion Loss

In a optical fiber coupler, the optical loss associated with that portion of the light which does not emerge from the operational ports of the device.

Excess Rate

In ATM, traffic in excess of the insured rate for a given connection. Specifically , the excess rate equals the maximum rate minus the insured rate. Excess traffic is delivered only if network resources are available and can be discarded during periods of congestion.

Excessive Zeros

More consecutive zeros received than are permitted for the selected coding scheme. For AMI-encoded T-1 signals, 16 or more zeros are excessive. For B8ZS encoded serial data, 8 or more zeros are excessive.


  1. Sometimes used to refer to a telephone switching center ” a physical room or building. Outside North America, telephone central offices are called "Public Exchanges."

  2. A geographic area established by a common communications carrier for the administration and pricing of telecommunications services in a specific area that usually includes a city, town or village. An exchange consists of one or more central offices and their associated facilities. An exchange is not the same as a LATA. A LATA consists of several adjacent exchanges.

  3. A term that refers to one of the Fibre Channel "building blocks," composed of one or more non-concurrent sequences for a single operation. See Fibre Channel.

Exchange Access

In the telephone networks, the provision of exchange services for the purpose of originating or terminating interexchange telecommunications. Such services are provided by facilities in an exchange area for the transmission, switching, or routing of interexchange telecommunications originating or terminating within the exchange area. The Telecommunications Act of 1996 defined exchange access as follows: the offering of access to telephone exchange services or facilities for the purpose of the origination or termination of telephone toll services. See also the Telecommunications Act of 1996.

Exchange Area

Geographic area in which telephone services and prices are the same. The concept of exchange is based on geography and regulation, not equipment. An exchange might have one or several central offices. Anyone in that exchange area could get service from any one of those central offices. It's good to ask which central offices could serve your home or office and take service from the most modern. There will be no difference in price between being served by a one-year old central office, or a 50-year old step- by-step central office.

Exchange Carrier

Any individual, partnership, association, joint-stock company, trust, government entity or corporation engaged in the provision of local exchange telephone service.

Exchange Carriers Association

An organization of long distance telephone companies with specific administrative duties relative to tariffs, access charges and payments. See Exchange Carriers Standards Association.

Exchange Carriers Standards Association

ECSA. According to their literature ECSA is "the national problem-solving and standards-setting organization where local exchange carriers, interexchange carriers, manufacturers, vendors and users rationally resolve significant operating and technical issues such as network interconnection standards and 800 database trouble reporting guidelines. The Association was created in 1983. The major committees sponsored by ECSA are The Carrier Liaison Committee (to coordinate and resolve national issues related to provision of exchange access); the Telecommunications Industry Forum (TCIF) (to respond to the growing need for voluntary guidelines to facilitate the use of new technology that offers cost savings throughout the telecommunications industry ” e.g. EDI, bar coding, automatic number identification); and the Information Industry Liaison Committee (IILC) (an inter industry forum for discussion and voluntary resolution of industry wide concerns about the provision of Open Network Architecture (ONA) services and related matters and Committee T1- Telecommunications (an accredited standards group under ANSI to develop technical standards and reports for US telecommunications networks. In October, 1993, The Exchange Carriers Standards Association changed its name to the Alliance for Telecommunications Industry Solutions (ATIS). It is based in Washington, D.C. See ATIS. www.atis.org.

Exchange Facilities

Those facilities included within a local access and transport area.

Exchange Network Facilities For Interstate Access


Exchange Message Record/Exchange Message Interface

EMR/EMI. The standard format used for exchange of telecommunications message information among Local Exchange Carriers for billable, non-billable, sample, settlement and study data. EMR format is contained in Telcordia Technologies (formerly Bellcore) Publication BR-010-200-010 CRIS Exchange Messaging.

Exchange Message Record

EMR. Bellcore standard format of messages used for the interchange of telecommunications message information among telephone companies. Telephone companies use EMR to exchange billable, non-billable, sample, settlement and study data. EMR formatted data is provided to all interdepartmental applications and to large customers (users) who request reproduced message records for control and allocation of their communication costs.

Exchange, Private Automatic Branch

EPABX. A private telephone exchange which transmits calls internally and to and from the public telephone network.

Exchange Service

A name that BellSouth gives to its local phone services, which it also calls Plain Old Telephone Service (POTS).

Exchange Termination

ET. In Integrated Services Digital Network (ISDN) nomenclature , ET refers to the central office link with the end user.


An RFID term. The reader is said to "excite" a passive RFID tag when the reader transmits RF energy to wake up the tag and enable it to transmit back.


The most boring and the most over-used word in the whole high-tech world. If I read another press release describing their shiny new product as "exciting," I'll puke. If it excites, I'll get excited. But I don't need (or want) to be told I'm about to be excited.


A memory management command-line option that tells the memory manager in an MS-DOS machine not to use a certain segment of memory. For example, you may exclude upper memory locations D200 through D800 (hexadecimal) because your network adapter card uses that space. The reciprocal term ” include ” specifically directs the memory manager to use an area of memory.


A PBX feature that prevents the attendant from silently monitoring a call once he/she has extended it.

Exclusive Hold

Only the telephone putting the call on hold can take it off. This feature assures that the call on hold will not be picked up by someone at another telephone who can then listen to your call.

Exclusive Hold Recall

When a call is placed on "Exclusive Hold" and is not picked up after a predetermined amount of time, you will hear a beeping at that phone, which indicates the call is still on hold.

Exclusive Or Private Unit

A circuit card installed in each key telephone set sharing the same line or intercom path that causes the first caller on the line to lock out (exclude) all other stations from using or listening in, until the line is released (or privacy feature is defeated by the active caller).


An intercity switched telephone service introduced by MCI in 1975. Execunet was the first dial-up switched service introduced by a long distance phone company in competition with AT&T. At that time, all of AT&T's competitors , including MCI, were selling full-time private lines and shared private lines. The service was named by Carl Vorder-Bruegge, MCI's VP marketing at that time and introduced and made successful by Jerry Taylor, who was MCI's regional manager in Texas and is now president of MCI. The service was the forerunner of what is today a $20 billion plus per year industry ” the non-AT&T provided switched long distance business. MCI no longer uses the word Execunet to describe its switched long distance service. It's just plain long distance. Jerry Taylor started Execunet using a 104-port Action WATSBOX in Dallas, Texas. He deserves a place in the history books, not just a dictionary.

Executable File

A computer program that is ready to run. Application programs, such as spreadsheets and word processors, are examples of executable files. Such files in PCs running MS-DOS and Windows usually end with the BAT, COM or EXE extension.


To begin a task.

Execution Time

The time needed to complete a task.

Executive Barge-In

See Executive Override.

Executive Busy Override

See Executive Override.

Executive Camp-On

A feature for use by executives or other privileged people. When they call a someone lowly, that low person hears a special distinctive tone or sees a special light or sees a special signal that their phone has been camped on by someone significant. These days many PBXs let you know who's calling ” even though you're on the phone. So executive camp-on is not that useful.

Executive Coach

A new "profession." One of them told me this: An Executive Coach is the person who helps coach you to your goals and keep you on track on a daily basis. An Executive Coach knows everything about the company. They could step in and run it in your absence, and therefore they can help you to focus on the most important aspects of building your business!

Executive Override

A feature of some telephone systems which permits certain users to intrude on conversations on other extensions. In some systems, executive barging- in will not be heard by the person outside the office, only the one inside the office. In some systems, such as the Mitel SX series with the Mitel Superset 4 phones, this feature activates the hands-free speakerphone of the called party, who is using his other line to speak on a normal phone conversation.


A telephone company definition. Equipment is said to exhaust when it has reached its most limiting network access line capacity level.

Exhaust Date

A telephone company definition. The exhaust date for an entity(s) refers to the calendar date on which the entity(s) will have reached the most limiting network access line capacity level.

Exit Border Node

An ATM term. The node that will progress a call over an outside link. This is the last node within a peer group to see this call.

Exit Event

An event occurring in an ASC (AIN Switch Capabilities) that causes call processing to leave a PIC (Point in Call). Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.


Exit Message. The seventh ISUP message. It's a message sent in the backward direction from the access tandem to the end office indicating that call setup information has successfully proceeded to the adjacent network. See ISUP and Common Channel Signaling.


Abbreviation for EXtension OutSide; a phone connected to a key system based in another building. The wiring belongs to the telephone company, even though the phone equipment may not. Unlike an OPX, the circuit between the two locations does not pass through a central office.


This region lies beyond an altitude of about 400km from the surface of the earth. The density is such that an air molecule moving directly outwards has an even chance of colliding with another molecule or escaping into space.

Expanded Memory

MS-DOS running on the Intel 80286, 80386, 80486 and Pentium family of microprocessors can only address one megabyte at one time. Expanded memory is memory located between base memory (either 512K or 640K) and one megabyte. Expanded memory is reserved by MS-DOS for "housekeeping" tasks such as managing output to the screen. As programs got larger and more hungry for memory (640K was no longer enough), people started jealously eyeing the memory between 640K and 1024K (one megabyte). The first technique was a standard called LIM-EMS, named after the three companies which developed it ” Lotus, Intel and Microsoft. Essentially LIM grabs 64K of the 640-1024 memory and uses it to swap pages of other memory in and out quickly. This fools DOS into thinking that it has actually more memory. LIM-EMS lets you work on bigger spreadsheets, and do other jobs faster.

There are many ways of using expanded memory, including special memory management application program or DOS 5.0 or higher. 80386, 80386SX, 80486 and Pentium computers can create expanded memory readily by using the EMS (expanded memory specification) driver provided with DOS, through Windows 3.xx or Windows 95, or through a memory manager such as Quarterdeck QEMM or Qualitas 386. To use expanded memory, a program must be EMS-aware or run under an environment such as Microsoft Windows. See also Extended Memory, which is memory above 1MB.

Expanded Spectrum

A cellular telephone term for having the full 832-channel analog cellular spectrum currently available to you, the user of the cellular phone.


That device in a transmission facility which expands the amplitude of received compressed signals to their approximate normal range. The receiving side of a compandor.


See Expander.


The switching of a number of input channels, such as telephone lines onto a larger number of output channels.

Expansion Carrier

An AT&T Merlin term. A carrier added to the control unit when the basic carrier cannot house all the modules needed. An expansion carrier houses a power supply module and up to six additional modules.

Expansion Slots

In a computer there are card slots for adding accessories such as internal modems, extra drivers, hard disks, monitor adapters, hard disk drivers, etc. Most modern PBXs are actually cabinets with nothing but expansion slots inside. Into these slots we fit trunk cards, line cards, console cards, etc. Some phone systems have "universal" slots, meaning you can put any card in any slot. Some phone systems have dedicated expansion slots, meaning that they expect only a certain card in that slot. In the PC industry, many manufacturers make cards for IBM and IBM compatible slots. In the phone industry, nobody makes cards for expansion slots in anyone else's phone system. A reader once asked me why? Here's the answer I gave him: The reason no one makes expansion cards for phone systems is because the phone industry doesn't trust anyone else. They don't issue open standards and the manufacturers are NOT committed to keeping their cages and their buses the same from one model of phone system to another. Manufacturers are afraid that outsider manufacturers would screw up the much-vaunted reliability of phone systems. And they have a point - people don't want to reboot phone systems like they reboot PCs. See also EISA and MCA.

Expansive Controls

Control applications that reroute traffic from congested portions of the network to trunk routes and switching systems having available capacity.

ExParte Presentation

An FCC definition. Any communication addressing the merits or outcome of a particular proceeding made to decision-making personnel (or in some proceedings, from the decision-making personnel), which (1) if written, is not served on the parties to the proceeding, or (2) if oral, is made without opportunity for the parties to the proceeding to be present.

Expedited Delivery

Option set by a specific protocol layer telling other protocol layers (or the same protocol layer in another network device) to handle specific data more rapidly.


See Shannon's Law.


What we all become when we're away from the office. See Expert System.

Expert System

A very sophisticated computer program consisting of three parts.

  1. A stock of rules or general statements, e.g. Some long distance phone calls are free. These rules are generally based on the collective wisdom of human "experts" who are interviewed.

  2. A set of particular facts, e.g. Three companies provide the bulk of long distance service in the United States.

  3. Most importantly, a "logical engine" which can apply facts to rules to reach all the conclusions that can be drawn from them ” one of which might be "Three companies give away long distance phone calls." (Which would be wrong.) The idea of expert systems is to help people solve problems. For example, Compaq is trying to improve its customer service by installing automated assistants that work on the principle that reasoning is often just a matter of remembering the best precedent. The simplest expert systems, according to the Economist Magazine, assume that their rules and facts tell them everything there is to know. Any statement that cannot be deduced from the system's rules and facts is assumed to be false. This can lead machines to answer "YES" or "NO," when they should say "I don't know." Slowly we are beginning to find ways of dealing with the inflexibility of machines. One such gadget is a "truth maintenance machine" invented by Dr. Jon Doyle of MIT. As each fact is fed into the system, Dr. Doyle's program checks to see if it (or the deductions derived from it) contradict any of the facts or deductions already in the system. If there is a contradiction, the machine works backward along its chain of reasoning to find the source and dispose of that troublesome fact or deduction . So the system maintains one consistent set of beliefs.

Explicit Access

In LAN Technology, explicit access is a shared access method that allows workstations to use the transmission medium individually for a specific time period. Every workstation is guaranteed a turn, but every station must also wait for its turn. Contrast with Contended Access. See also CSMA.

Exponential Back-Off Delay

The back-off algorithm used in IEEE 802.3 systems by which the delay before retransmission is increased as an exponential function of the number of attempts to transmit a specific frame.

Exponential Holding Time

A telephone company term. A great number of calls are assumed to have a relatively short holding time while decreasing numbers of calls are assumed to have longer and longer holding times out to the point where a very small number of calls exhibit exceedingly long holding times.


Imagine you have a software program, like a spreadsheet or a database. And you have information in that program. Let's say it's Microsoft Word or Lotus 123. And you want to get it into a different program, say to give it to a workmate who uses WordPerfect or Excel. You have to convert it from one format to another. From Word to WordPerfect or from Lotus to Excel. That process is typically called "exporting." And you'll typically see the word "EXPORT" as a choice on one of your menus . The opposite is called importing. See Import.

Export Script

First read my definition of EXPORT. An export script is a series of specifications which control the export process. It contains the fields to be sent, which records to be sent, the name of file to send as well as the name of the import script (if there is one) located at the receiver's end which will control the merge. See Export.

Export Server

A Windows NT term. In directory replication, a server from which a master set of directories is exported to specified servers or workstations (called import computers) in the same or other domains.

Express Call Completion

Someone calls an information operator. "What is the name?" the operator answers. "Here is the number. Would you like me to get that number for you now? If so, please hit 1." Express Call Completion lets the operator complete the call for you while you're on line. Express Call Completion was begun in September of 1990 by Pacific Bell using a Northern Telecom central office. Express Call Completion is part of Nortel Networks' Automated Directory Assistance Call Completion (ADACC) software and Traffic Operator Position Systems Multipurpose (TOPS MP).

Express Client Installation

An Internet Access Term. A client installation scripting utility that enables network managers to establish defined defaults that make client installation and deployment easier.

Express Orderwire

A permanently connected voice circuit between selected stations for technical control purposes.


See Extension.


A verb used by the phone industry to describe an operator transferring a call to a telephone extension. The word is used thus: The operator extended the call to Mr. Smith on extension 200. "Putting a call through" is a clearer way of saying "extending" a call. The word "extend" probably comes from the old days when the operator extended her arm to plug you in on her cordboard.

Extended Addressing

In many bit-oriented protocols, extended addressing is a facility allowing larger addresses than normal to be used. In IBM's SNA, the addition of two high-order bits to the basic addressing scheme.

Extended Area Service

A geographic area beyond the local service area to which traffic is classified as local for selected customers, i.e., telephone service that allows subscribers in one exchange to call subscribers of another exchange without a toll charge. Sometimes subscribers may be given the option of paying more for the privilege of calling these more distant phone companies. Sometimes, they have no option. The local public service commission deems EAS a "good idea." And, typically, everyone's monthly rate for basic telephone service goes up.

Extended ASCII

ASCII is a seven bit code. Extended ASCII adds an eighth bit. The eighth Bit is called a parity bit and is used for error checking, not error correction. See ASCII.

Extended Binary Coded Decimal Interchange Code

EBCDIC. (Pronounced Eb-Si-Dick.) An IBM standard of coding characters. It's an 8-bit code and can represent up to 256 characters. A ninth bit is used as a parity bit. See Parity and EBCDIC.

Extended BIOS Data Area

In PCs, extended BIOS data area is 1KB of RAM located at 639KB. It is used to support extended BIOS functions including support for PS/2.

Extended Call Management

A Nortel Networks term for a collection of features being added to its DMS Meridian central office Automatic Call Distribution (ACD) service. Using Switch-to-Computer Applications Interface (SCAI), ECM will work with user-provided computer equipment to integrate call processing, voice processing (recorded announcements, voice mail and voice response) and data processing. For example, ECM will allow an outboard computer device to coordinate the presentation of customer data on the ACD agent's computer screen with an incoming call. The D channel of an ISDN Basic Rate Interface (BRI) serves as the transport mechanism from the DMS-100 central office switch to an outboard computing device. Communication is peer-to-peer, meaning that neither the switch or the computer is in a "slave" relationship to the other. The application layer messaging ” i.e. layer 7 messaging as defined by the Open Systems Interconnection (OSI) reference model ” is in the Q.932 format and is designed to conform to the T1S1 SCAI message protocol.

Extended Character Set

The characters assigned to ASCII codes 128 through 255 on IBM and IBM-compatible microcomputers. These characters are not defined by the ASCII standard and are therefore not "standard." See Extended Graphics Character Set.

Extended Definition Television

EDTV. Television that includes improvements to the standard NTSC television system, which improvements are receiver-compatible with the NTSC standard, but modify the NTSC emission standards. Such improvements may include

  1. a wider aspect ratio,

  2. higher picture definition than distribution-quality definition but lower than HDTV, and/or

  3. any of the improvements used in improved-definition television. When EDTV is transmitted in the 4:3 aspect ratio, it is referred to simply as "EDTV." When transmitted in a wider aspect ratio, it is referred to as "EDTV-Wide."

Extended Digital Subscriber Line

The ISDN EDSL combines 24 B-channels and one 64-Kbps D-channel on a single line, ISDN primary rate interface.

Extended Graphics Character Set

The characters assigned to ASCII codes 128 through 255 on IBM and IBM-compatible microcomputers. These characters are not defined by the ASCII standard and are therefore not "standard." The original ASCII code used a seven bit one-or-zero code. There are two to the seventh power, or 128 possible combinations. The IBM PC uses a 16-bit CPU with an eight bit data bus and thus transmits data internally in eight bit bytes. Instead of using the seven bit ASCII code, the PC uses the equivalent eight bit code, by simply making the left most digit, a zero. In seven bit code, an R is 1010010. In 8-bit, it's 01010010. The only difference between the first 128 characters and the second 128 characters is that in the second, the first bit is a 1.

Extended Hamming Code

See Hamming Code.

Extended LAN

A term used to describe a network that consists of a series of LANs connected by bridges.

Extended Life Battery

Toshiba's wonderful name for a battery for a laptop that's physically larger than the normal one, costs more than the normal one and lasts longer than the normal one. Extended life batteries make lightweight laptops into heavyweight laptops.

Extended Key Code

The two digit code that represents pressing a key outside the typewriter portion of the keyboard, such as a function key, cursor-control key or combinations of CTRL (control) and ALT keys with another key. The first number is always 0 (zero) and is separated from the second number by a semicolon.

Extended LAN

A collection of local area networks connected by protocol independent devices such as bridges or routers.

Extended Memory

Memory beyond 1 megabyte in 80286, 80386, 80486 and Pentium computers. Windows uses extended memory to manage and run applications. Extended memory can be used for RAM disks, disk caches, or Microsoft Windows, but requires the processor to operate in a special mode (protected mode or virtual real mode). With a special driver, you can use extended memory to create expanded memory. Extended memory typically is not available to non-Windows applications or MS-DOS. See also Expanded Memory.

Extended Superframe Format

ESF. A new T-1 framing standard used in Wide Area Networks (WANs). With this format 24 frames ” instead of 12 ” are grouped together. In this grouping, the 8,000 bps frame is redefined as follows:

  • 2,000 bps for framing and signaling to provide the functions generally defined in the D-4 format.

  • 2,000 bps are CRC-6 (Cyclic Redundancy Check-code 6) to detect logic errors caused by line equipment, noise, lightning and other interference. Performance checking is done by both the carrier and the customer without causing any interference with the T-1 traffic.

  • 4,000 bps are used as a data link. This link is to perform functions such as enhanced end-to-end diagnostics, networking reporting and control, channel or equipment switching, and/or optional functions or services. See also T-1 Framing and D-4 Framing.

Extended Superframe Monitoring Unit

ESFMU. An MCI definition. Placed on customer data circuits to provide performance monitoring throughout MCI's Digital Data Network.

Extended Telephony Level

The lowest level of service in Windows Telephony Services is called Basic Telephony and provides a guaranteed set of functions that corresponds to "Plain Old Telephone Service" (POTS - only make calls and receive calls). The next service level is Supplementary Telephone Service providing advanced switch features such as hold, transfer, etc. All supplementary services are optional. Finally, there is the Extended Telephony level. This API level provides numerous and well-defined API extension mechanisms that enable application developers to access service provider- specific functions not directly defined by the Telephony API. See Windows Telephony Services.

Extended Text Mode

Standard text mode is 80 columns wide. So-called extended text mode is 132 columns wide. This mode allows you to view more text on- screen when using such applications as Lotus 1-2-3.


In strictest terms, the word means "capable of being extended." When Microsoft introduced its At Work operating system on June 9, 1993 it said that one of the operating system's key features was that it was "extensible." Microsoft's explanation: The software is designed to allow both manufacturers and customers to add new features. For example, local area network connectivity will be able to be added easily by installing an optional LAN hardware module and a software driver. Additional memory will be able to be added to the system, and the system will automatically make use of this memory. New image-processing software and communications protocols will be able to be added on the premises, and it will even be able to be done over the phone line, allowing manufacturers to create basic models that can be enhanced in many different ways to fit the needs of different user groups.

Extensible Authentication Protocol

See EAP.


This means it's easy to add new technologies without reinventing the wheel.


  1. An additional telephone connected to a line. Allows two or more locations to be served by the same telephone line or line group. May also refer to an intercom phone number in an office.

  2. The optional second part of an PC computer filename. Extensions begin with a period and contain from one to three characters. Most application programs supply extensions for files they create. Checking a file's extension often tells you what the file does or contains. For example, most BASIC files use a filename extension of .BAS. Most backup files have an extension of .BAK. MS-DOS programs have .EXE or .COM. dBASE database files have the extension .DBF and .DBT. Paradox files have the extension .DB. Files of sounds have their own extensions. Here are the typical extensions on sound files of various computers:

    Microsoft Windows ” .wav

    Apple ” .aif

    NeXT ” .snd

    MIDI ” .mid and .nni

    Sound Blaster ” .voc

    Here are the typical extensions on graphics formats: .TIFF, .EPS, .CGM, .PCX, .DRW, .WMF, and .BMP

    Extensions are also short for domain name extensions. See November 16, 2000: ICANN, the authority that governs global Internet domain name system, has approved seven new domains extensions, in addition to .com, .net and .org. These new extensions are the first new global Internet domains approved by ICANN in over a decade .

    1. .biz

    2. . info

    3. .name

    4. .pro

    5. .aero

    6. .coop

    7. .museum

Extension Cord

A multi-conductor, male/ female modular line cord generally used to permit greater separation between the Communications Outlet and the telephone equipment. Available in various lengths up to 25 feet. May be of tinsel or stranded wire construction.

Extensions to Unix

Extensions to UNIX are additional features or functions not found in the standard UNIX implementation. The extension are classified either as "open extensions" or "proprietary extensions." An "open extension" usually consists of a surface addition, such as a driver for peripheral or a software patch for a new mode of I/O. The "open extension" is transparent to standard UNIX and its application programs. The "proprietary extension" is for the implementation of custom hardware or software. It results in a version of UNIX that is not transparent to UNIX and its applications.


An ATM term. Denotes that an item (e.g., link, node, or reachable address) is outside of a PNNI routing domain.

Exterior Link

An ATM term. A link which crosses the boundary of the PNNI routing domain. The PNNI protocol does not run over an exterior link.

Exterior Reachable Address

An ATM term. An address that can be reached through a PNNI routing domain, but which is not located in that PNNI routing domain.

Exterior Route

An ATM term. A route which traverses an exterior link.

External Data Representation

See XDR.

External F-ES

A Fixed End System (F-ES) connected to the CDPD network outside the administrative domain of the service provider.

External Interface

A cellular radio term. The Cellular Digital Packet Data (CDPD)- based wireless packet data service provider's interface to existing external networks. The external application service providers communicate with CDPD subscribers through this external interface.

External Memory

Storage devices, such as magnetic disks, drums or tapes which are outside (externally attached) to the main telephone or computer system.

External Modem

A modem external to the computer, it sits in its own little box connected to a computer through the computer's serial port. Compare with an internal modem, which typically comes on one printed circuit card and is placed into one of the computer's expansion slots and thus connects to the computer through the computer's "backplane." Internal modems cost less because they don't need any external housing and separate power supply. But because they're mounted inside the computer, it's harder to see what they're doing. You can't see the various status lights, like OH (for Off-Hook) and CD (for Carrier Detect). They also take up valuable slots instead of a serial port.

External Photoeffect

In fiber optics, an external photoeffect consists of photon- excited electrons that are emitted after overcoming the energy barrier at the surface of a photo- emissive surface.

External Storage

See also External Memory.

External Timing Reference

A timing reference obtained from a source external to the communications system such as one of the navigation systems. Many of which are referenced to Coordinated Universal Time (UTC).

External Viewer

This is the program that is launched or used by Web browsers for presenting graphics, audio, video, VRML, and other multimedia found on the Internet. Sometimes referred to as helper applications. Usually when you initially set up your browser you configure what external viewers you want to use by associating a program with a file type or extension. This way the browser knows what to do when these files are "clicked on" by the user.




An extranet, coined by Bob Metcalfe in the April 8, 1996 issue of InfoWorld, is a Internet-like network which a company runs to conduct business with its employees, its customers and/or its suppliers. Extranets typically include Web sites that provide information to internal employees and also have secure areas to provide information to customers and external partners like suppliers, manufacturers and distributors . A company might place a call for product on its extranet's web site. Its suppliers will check the site regularly and bid on the product. It is called an extranet because it typically uses the technology of the public Internet (TCP/IP and browsers) and customers and suppliers often access the extranet through the Internet via their local ISP ” Internet Service Provider. But an Extranet is not a public entity. You typically need accounts and passwords, typically issued by the firm running the Extranet. The word Extranet, however, is a term in evolution. In the October 21, 1996 issue of InfoWorld, Bob Metcalfe defined Extranets as IP networks through which companies run Web applications for external use by customers. He explained that ISPs have deployed private networks (i.e. extranets) which operate on the same principles and make use of the same network technologies as the Internet, but are external to it. Access to the Internet can be gained through an Extranet. Extranets, he said, were for electronic commerce. See also Internet and Intranet.

Extremely High Frequency

EHF. Frequencies from 30 GHz to 300 GHz.

Extremely Low Frequency

ELF. Frequencies from 30 Hz to 300 Hz.

Extrinsic Joint Loss

For an optical fiber, that portion of a joint loss that is not intrinsic to the fibers, e.g., loss caused by end separation, angular misalignment, or lateral misalignment.


Method of continuously forcing plastic, rubber or elastometer material through an orifice to apply insulation or jacketing over a conductor or cable core.

Eye Candy

  1. A term used in information technology for visual elements displayed on computer monitors that are aesthetically pleasing or attention-getting.

  2. A popular plug-in for Adobe Photoshop that provides extra "filters" for simulating various effects.

  3. Donald Trump's girlfriends. They're all gorgeous. That's their function. See also Arm Candy and Wrist Candy.

Eye Pattern

An oscilloscope display used to visually determine the quality of an equalized transmission line signal being received. So called because portions of the pattern appearing on the scope resemble the elliptical shape of the human eye.

Eye Phone

Several researchers are studying something they call "virtual reality." One version of it, a system developed by a company called VPL Research, Redwood City, CA, is based around three things: a three-dimensional display worn on the head (called an Eye Phone), an electronic glove (the Data Glove) and a high-speed computer. The whole system cost $250,000 in the fall of 1990, which may be one reason we haven't seen or heard much of it since.


A viewing audience. "There are plenty of new eyeballs available in this time slot." Also refers to the number of people visiting your Web site.

Eyeball Shot

Also called microwave link. The link is made by two radio transceivers equipped with parabolic dish antennas pointed at each other. The transmissions can be carried on many bandwidths including DS1, DS2, DS3, STS1 and OC1. The range varies from 0-50 miles depending on the dish size, weather and transmitter power.


Software developed under direction of Fabrice Florin and Peter Maresca of Apple Computer's Discovery Studio. EZTV was an interactive system intended to enable consumers to order movies, go shopping and play games on their TV sets.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

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