Decide-Dialing Plan


A deadly computer virus.


Our normal numbering system. It is to the base 10.


Use of a cryptological process involving a "key" to recover information which has been " enciphered ." See Cipher.

Decision Circuit

A circuit that measures the probable value of a signal element and makes an output signal decision based on the value of the input signal and a predetermined criterion or criteria.

Decision Feedback Equalization

A technique used in high-speed transmission systems to reduce the likelihood of error propagation. Such systems can suffer from intersymbol interference (ISI), which is a type of interference caused when adjacent symbols (values), interfere with each other and cause errors in the data stream.

Decision Instant

In the reception of a digital signal, the instant at which a decision is made by a receiving device as to the probable value of a signal condition.

Decision Support System

DSS. Computerized systems for transforming data into useful information, such as statistical models or predictions of trends, which is used by management in the decision-making process. There are several aspects of the best decision support systems: First, they are connected to mainframe databases. Second, they are accessible by executives from their desktops. Third, there are usually lots of programs for producing graphs, charts and writing simple reports , i.e. for the executives to extract and portray information in forms that are most useful to them.

Decision Tree

The organization of the call flow for a particular application, expressed in a tree-like logic structure.

Deck of Cards

A "card" is a discrete unit of data specifically designed to be read easily on the small screen of a handheld wireless device such as a cell phone, pager, or PDA (Personal Digital Assistant). A card can be for entering data, displaying data, or listing indexes or available menu options. Packet radio networks generally send a "deck of cards" in a single data packet for reasons of efficiency, as the individual cards are small in terms of byte count.


A device that converts information from one form to another ” typically from analog to digital and vice versa. See Decoding.

Decode Status Flag

A cellular industry term . A 5-bit flag used by the CDPD Mobile Data Base Station (MDBS) in the forward channel transmission to indicate the decoding status of Reed-Solomon blocks received on the reverse channel from the CDPD Mobile End System (M-ES).


Changing a digital signal into analog form or into another type of digital signal. The opposite of Encoding. See also MODEM. Decoding and coding should not be confused with deciphering and ciphering. See DES.


In optics, that effect wherein a beam of parallel light rays is caused to diverge or converge from parallelism. Any of a large number of factors may cause this effect, e.g., refractive index inhomogeneities, occlusions, scattering, deflection , diffraction , reflection, refraction.


The process of reformatting multi-column documents into a signal column. Generally, when you are processing a document for use in a word processing program, a single column of text is preferable to multiple columns .


To decompile is to convert executable (ready-to-run) software code (some- times called object code) into some form of higher-level programming language so that it can be read by a human. Decompilation is sort of reverse engineering that does the opposite of what a compiler does. The tool that accomplishes this is called a decompiler. A similar tool, called a disassembler, translates object code into assembler language. There are a number of different reasons for decompilation or disassembly, such as understanding a program, recovering the source code for purposes of archiving or updating, finding viruses, debugging programs, and translating obsolete code. Decompilation was first used in the 1960s to make easy the migration of a program from one platform to another. Decompilation doesn't always work for a number of reasons. It is not possible to decompile all programs, and data and code are difficult to separate, because both are represented similarly in most current computer systems. The meaningful names that programmers give variables and functions (to make them more easily identifiable) are not usually stored in an executable file, so they are not usually recovered in decompiling.


Decompression is the process of expanding a compressed image or file so it can be viewed , printed, faxed or otherwise processed .


To convert encrypted text into its equivalent plain text by means of a cryptosystem. This does not include solution by cryptanalysis. The term decrypt covers the meanings of decipher and decode.


Digital European Cordless Telecommunication. The pan-European wireless standard based on time division multiple access used for limited-range wireless services. Based on advanced TDMA technology, and used primarily for wireless PBX systems, telepoint and residential cordless telephony today, uses for DECT include paging and cordless LANs. DECT frequency is 1800-1900 MHz. Stop press; the old meaning of the word DECT was "Digital European Cordless Telephones" but since the DECT standard also has spread to China and South America the correct definition is now "Digital Enhanced Cordless Telephones". See also Generic Access Profile.


A facility or equipment system or subsystem set aside for the sole use of a specific customer.

Dedicated Access

A connection between a phone or phone system (like a PBX) and an IntereXchange Carrier (IXC) through a dedicated line. All calls over the line are automatically routed to a particular IXC.

Dedicated Access Line

DAL. See Dedicated Access Line Service.

Dedicated Access Line Service

A type of service often used by large companies which have a direct telephone line going directly to the long distance companies' "Point of Presence" (POP), thereby bypassing the local telephone company and reducing the cost per minute. Often referred to as "T-1" service.

Dedicated Array Processor

A microprocessor on a hardware-based RAID array that controls the execution of RAID array-specific functions, such as rebuilding. See RAID.

Dedicated Attendant Link

Assures that there will always be an intercom link available for your attendant or receptionist or operator to announce incoming calls.

Dedicated Bypass

A connection between a phone or phone system (like a PBX) and an IntereXchange Carrier (IXC) through a dedicated line that is not provided by the dominant local provider of local phone service. For example, I live in New York. I might order a leased T-1 to MCI. If that line is not provided by Verizon, it is "dedicated bypass." Such bypass circuits are often cheaper and better quality than what the dominant local carrier can provide.

Dedicated Channel Or Circuit

A channel leased from a common carrier by an end user used exclusively by that end user . The channel is available for use 24 hours a day, seven days a week, 52 weeks of the year, assuming it works that efficiently .

Dedicated Circuit

A circuit designated for exclusive use by specified users. See also Dedicated Channel.

Dedicated Feature Buttons

The imprinted feature buttons on a telephone: Conf or Conference, Drop, HFAI (Hands Free Answerer on Intercom), Hold, Mute or Microphone, Speaker or Speakerphone, Transfer, Message, and Recall.

Dedicated Inside Plant

DIP. Inside plant is the portion of a LEC's (Local Exchange Carrier's) plant, or physical facilities, that are located inside its buildings . Such inside plant comprises a wide variety of equipment such as channel banks, multiplexers, switching systems, Main Distribution Frames (MDFs) and Intermediate Distribution Frames (IDFs). Dedicated Inside Plant, most commonly, is a term describing an IDF which is dedicated to the purpose of providing a CLEC (Competitive LEC) with a point of interconnection between the local loops it has leased from the ILEC (Incumbent LEC) for purposes of customer access, and the facilities which the CLEC uses to serve those customers. The dedicated IDF also is known as a Single Point of Termination (SPOT) frame. From the SPOT frame, the circuit commonly is directed to a secure enclosure in which the CLEC has collocated in the ILEC building a concentrator or multiplexer which is connected to a high-speed transmission link which hauls traffic to the CLEC's own facilities-based network. A common SPOT is a shared dedicated IDF for use by multiple CLECs which are unable to cost justify a SPOT of their own ” the cost of the SPOT, plus a reasonable profit margin ” is passed on to the CLEC by the ILEC. See also Collocation and Dedicated Outside Plant.

Dedicated Line

Another name for a private leased line or dedicated channel. A dedicated line provides the ability to have a constant transmission path from point A to point

B. A dedicated line may be leased or owned. It may be assigned a single purpose, such as monitoring a distant building. It may be part of a network, with the ability for many to dial into it. It may be a tie-line between your offices or it may be a line to a long distance carrier. In this case, you do not have to dial a local connection number or put in an authorization code. A WATS line is in effect a Dedicated Line to AT&T or whomever you purchased WATS from.

Dedicated Machine

A computer designed to run only one program or do one thing. This machine cannot easily be re-programmed to do another task, as, for example, a general-purpose machine can. A general-purpose machine, however, can be dedicated to running only one task if programmed to do so.

Dedicated Mode

When a file server or router on a local area network is set up to work only as a file server or router, it runs in dedicated mode.

Dedicated Outside Plant

DOP. Outside plant is the local loop facilities which connect the customer premises to the LEC (Local Exchange Carrier) network. Typically, the connection is to the LEC central office (CO) exchange. Dedicated outside plant, at the extreme, means that each customer premises has one or more local loops which connect directly to the "wire center" in which the CO is housed. While this approach is copper - intensive , it allows local loops to be activated remotely, as it is not necessary to "roll a truck" in order to make cross connections between various trunk and feeder facilities in the outside plant network in order to effect the connection. Once the initial investment is made, therefore, the ongoing installation and maintenance expenses are much reduced. In the context of a competitive local exchange environment, the CLEC (Competitive LEC) commonly desires to lease from the ILEC (Incumbent LEC) a dedicated outside plant in the form of a "dry copper" circuit. A dry copper circuit is one which is has no electronics (e.g., load coils, repeaters or subscriber carrier systems) between the wire center and the customer premises. Such electronics interfere with the provisioning and support of most data services, including high-speed DSL (Digital Subscriber Line) services, which many of the CLECs are interested in providing. See also CLEC, Dedicated Inside Plant, Dry Copper, DSL, ILEC.

Dedicated Server

A computer on a network that performs specialized network tasks , such as storing files. The word "dedicated" means that the computer is used exclusively as a server. It is not used as a workstation, which means no one is sitting in front of it, using it. A dedicated server sits all alone, attached to its network, working happily all by itself.

Dedicated Service

A communication network devoted to a single purpose or group of users, e.g., AUTOVON, FTS. It may also be a subset of a larger network, e.g., AUTOVON, FTS.

Dedicated Trunk

A trunk which bypasses the Attendant Console and rings through to a particular phone, hunt group or distribution group.


A file processing term for removing duplicate records from the base file. Duplicate information my be present in the same file or could occur through merging several files from different sources.

Deep Computing

According to IBM, deep computing is supercomputer-scale processing that combines massive computation and very sophisticated software algorithms to attack problems previously beyond the reach of information technology.

Deep Fiber

A service of Reltec Corp. Means Fiber To The Curb (FTTC). Specifically means within 500 feet of the premises, they say that they can deliver 155 Mbps, fully symmetric bandwidth. Because it's manufacturer-specific, the term doesn't belong in this dictionary. But somebody asked, and it's a neat term...

Deep Space

Space at distances from the Earth approximately equal to or greater than the distance between the Earth and the Moon.

Deep UV

Printed circuits are made by optical lithography, by shining light through a negative, or mask. In the beginning, it was visible light, but lately it's been made with more precise ultraviolet light, which can print lines as thin as 0.15 micron wide. They call this light "deep uv" and it is ultraviolet light emitted by an exciter or pulsing laser.

Defacto Standards

Standards, widely accepted and used, but lacking formal approval by a recognized standards organization. The Hayes AT command set, MS-DOS, Windows , TCP/IP etc. are defacto standards.


  1. The default is a factory-set hardware of software setting or configuration. It is the preset value that the program or equipment comes with. It will work with default values in the absence of any other command from the user. For example, communications software programs, such as Crosstalk, Blast, etc., have as their default settings 300 baud, 8 bit, one stop bit, no parity. If you want to run at 1,200 baud, you have to change that "default" setting.

  2. When you sign a contract with someone and that contract says you will do something and you don't do it, you are technically in "default" on your contract. What that will then mean depends on the person with whom you signed the contract. For example, if you didn't pay them the money you were meant to, they might file to place your company in bankruptcy. Or perhaps you might work out a deal to skip a payment or two and take you out of default.

Default Carrier

Generic name given to the long distance carrier which will carry the traffic of customers who haven't presubscribed to a long distance carrier.

Default Node Representation

An ATM term. A single value for each nodal state parameter giving the presumed value between any entry or exit to the logical node and the nucleus.

Default Route

  1. A routing table entry that is used to direct any data addressed to any network numbers not explicitly listed in the routing table.

  2. Entry in a routing table that can redirect any frames for which the table has no definitive listing for the next hop.

Defense Data Network

DDN. The Department of Defense integrated packet switching network capable of worldwide multilevel secure and non-secure data transmission.

Defense in Depth

A term borrowed from the military used to describe defensive measures that reinforce each other, hiding the defenders activities from view and allowing the defender to respond to an attack quickly and effectively. In the network world, defense in depth describes an approach to network security that uses several forms of defense against an intruder and that does not rely on one single defensive mechanism.

Defense Switch Network

See DSN.

Deferred Processing

Performing operations as a group or batch, all at once. Using batch mode, you can quickly prescan your documents, capturing just the image of each page, then perform recognition on these images later, freeing your computer for interactive work.


A figure of merit for image quality. For video-type displays, it is normally expressed in terms of the smallest resolvable element of the reproduced received image.


A family of digital PBX platforms first introduced and marketed in 1990 by AT&T, then by spinoffs Lucent Technologies and currently Avaya Communication. It is a descendant of the System 75 and 85 architectures first introduced in 1983.


Some automatic call distributors can be programmed to give callers a busy signal if the waiting time is past a certain threshold for callers to your 800 numbers (since you pay for all the waiting time). This is called "deflection" by Intecom and may have another name for other manufacturers. Of course the financial benefit of this must be weighed against the impression it gives your callers.

Deflection Routing

See Hot Potato Routing.


To demagnetize. To degauss a magnetic tape means to erase it. See Degaussing Coil and Degausser.

Degaussing Coil

Degaussing is to demagnetize. A degaussing coil is a long piece of wire bent into the shape of a circle. When a CRT becomes magnetized an area of the screen becomes discolored. If you wave the degaussing coil around this area, the screen becomes demagnetized and the picture quality improves .


Device to demagnetize a color picture tube for color purity. See Degaussing Coil.


In communications, that condition in which one or more of the established performance parameters fall outside predetermined limits, resulting in a lower quality of service.

Degraded Service State

The condition wherein degradation prevails in a communication link. For some applications e.g., automatic switching to a non degraded standby link, degradation must persist for a specified period of time before a degraded service state is considered to exist.

Degree Of Coherence

A measure of the coherence of a light source.

Degree Of Isochronous Distortion

In data transmission, the ratio of (a) the absolute value of the maximum measured difference between the actual and the theoretical intervals separating any two significant instants of modulation (or demodulation) to (b) the unit interval. These instants are not necessarily consecutive. The degree of isochronous distortion is usually expressed as a percentage. The result of the measurement should be completed by an indication of the period, usually limited, of the observation.

Degree Of Start-Stop Distortion

  1. In asynchronous data transmission, the ratio of (a) the absolute value of the maximum measured difference between the actual and theoretical intervals separating any significant instant of modulation (or demodulation) from the significant instant of the start element immediately preceding it to (b) the unit interval.

  2. The highest absolute value of individual distortion affecting the significant instants of a start-stop modulation. The degree of distortion of a start-stop modulation (or demodulation) is usually expressed as a percentage.


A term used in the secondary telecom equipment business. The shutoff and disconnection of power and the disassembly of the equipment to prepare for its removal from the building. A properly executed deinstallation will include all necessary parts for the reassembly, operation, maintenance and acceptance of the switch and any of its components at the next location. See also de-install.


A device for reducing jitter in a digital signal, consisting essentially of an elastic buffer into which the signal is written and from which it is read at a rate determined by the average rate of the incoming signal. Such a device is largely ineffective in dealing with low-frequency impairments such as waiting-time jitter.

Dejure Standard

A dejure standard that involve committees , such as, ISO, ANSI, IEEE, ITU to name a few. Because of the number of people involved and the nature of the standards process, a consensus must be reached, usually by a vote, therefore this type of standard takes a long time to complete. By contrast, see Defacto.


Data Encryption Key. The key by which one can unlock an encrypted message. There are "private" and "public" keys. See Encryption.


The wait time between two events, such as the time from when a signal is sent to the time it is received. There are all sorts of reasons for delays, such as propagation delays, satellite delays, the additional time introduced by the network in delivering a pack- et's worth of data compared to the time the same information would take on a full-period, dedicated point-to-point circuit, etc. See also Latency.

Delay Announcements

These are pre-recorded announcements to incoming callers that they are being delayed and being placed in an ACD queue. Sample: "Please wait. All our agents are permanently busy. You are being placed on Eternity Hold. Don't go away or you'll never be allowed back." Some announcements are giving callers sales pitches and some idea of how long they'll have to stay on line until someone helps them.

Delay Distortion

The difference, expressed in time, for signals of different frequencies to pass through a phone line. Some frequencies travel slower than others in a given transmission medium and therefore arrive at the destination at different times. Delay distortion is measured in microseconds of delay relative to the delay at 1700 Hz. Also called Envelope Delay.

Delay Encoding

A method of encoding binary data to form a two-level signal. A binary zero causes no change of signal level unless it is followed by another zero, in which case a transition takes place at the end of the first bit period. A binary "1" causes a transition from one level to the other in the middle of the bit period. Used primarily for encoding of radio signals since the spectrum of the encoding of signal contains less low frequency energy than an NRZ signal and less high frequency energy than a biphase signal.

Delay Equalizer

A corrective piece of electronic circuitry designed to make communications circuit delays constant over a desired frequency range. A delay equalizer is a device that adds a delay to analog signals, which will travel through a medium faster than other frequencies used to transmit portions of the same data. The objective is to create a medium that transfers the information on all the used frequencies in the same time over the same distance, thus eliminating transmission delay distortion.

Delay Length Call Factor

DLCF. An intermediate factor found in an Erlang C table that defines service level as a delay factor. It measures the delay of a call compared to the average handle time (AHT) of a call. It is used to determine the number of staff necessary to meet service level goals. For example, if the desired delay time is 20 seconds and is divided by a AHT of 150 seconds, the corresponding service level to locate in the Erlang table is 0.133. The table will give a staffing level.

Delay Line

A transmission line, or equivalent device, designed to introduce delay.

Delay Modulation

A modulation scheme that uses different forms of delay in a signal element. Frequently used in radio, microwave and fiberoptic systems.

Delay Skew

The difference in timing of the transmission of signals between pairs in a cable. Delay skew is an issue when multiple pairs in a cable are used to support a single transmission. Examples include 100Base-T, which uses as many as four pairs to support a connection between a LAN hub and an attached device. By splitting the transmission across multiple pairs, the distance between the hub and the attached device can be increased considerably, as each element of the split signal runs at a lower carrier frequency than would the native signal over a single pair. This enhanced performance is due to the fact that lower frequency signals suffer less from the effects of attenuation (loss of signal strength). Delay skew, however, can have significantly adverse effects on this approach. See also 100Base-T and Attenuation.

Delay Spread

See 802.11a.

Delay, Absolute

The time elapsed between transmission of a signal and reception of the same signal.

Delayed Call Forwarding

A phone system feature in which you have your incoming calls forwarded to another number only after several rings.

Delayed Calls

The fraction of calls delayed longer than a given time for service are called delayed calls. A telephone company definition.

Delayed Delivery

Hold a message for delivery later. Just as the words say.

Delayed Delivery Facility

A facility that employs storage within the data network whereby data destined for delivery to one or more addresses may be held for subsequent delivery at a later time.

Delayed Ring Transfer

An optional KTU facility that provides for automatic transfer to the ringing signal from a principal telephone set to the attendant telephone station after an adjustable number of rings.

Delayed Sending

A feature of fax machines which allows the machine to be programmed to send its transmissions at a later time ” to take advantage of lower phone rates, for example.

Delayed Transmission

A fax machine feature that allows a document to be transmitted automatically at a specific time.


A character that separates the parts of a DOS command. For example, a backslash is the delimiter between subdirectory names. Also, the character (typically a comma or tab) that separates field items in a database.

Delivered Block

A successfully transferred block.

Delivered Overhead Bit

A bit transferred to a destination user, but having its primary functional effect within the telecommunication system.

Delivered Overhead Block

A successfully transferred block that contains no user information bits.

Delivery Confirmation

Information returned to the originator indicating that a given unit of information has been delivered to the intended addresses.

Delivery Envelope

An X.400 term.


Digital Ethernet Local Network Interconnect. An industry adopted term indicating a multiport transceiver, also known as a fan-out, and generally limited to AUI connections in Ethernet. Originally, this was a product introduced by Digital Equipment Corporation as the DEC Local Network Interconnect.

Delphi Forecasting

One of the silliest methods of forecasting the future. Namely, to ask a bunch of alleged experts (often academic eggheads) what they think might happen and then averaging out their opinions , sort of.


  1. The mathematical term for a finite increment in a variable. Once a value has been established, the delta is the difference between that value and the succeeding value. The delta can be either positive or negative. The benefit of delta modulation, for instance, is that the difference between the subject value and a previous value can be expressed in fewer bits than can the absolute subject value ” it is a form of compression, in effect, yielding better utilization of expensive network bandwidth. See Delta Modulation.

  2. A wiring system for distributing and utilizing three phase electrical power. In this system, three power carrying conductors are used, possibly with a fourth safety ground wire. The voltage between any two of the three power wires is the rated distribution voltage, which is most commonly 380 to 415 VAC in most countries or 208 VAC in North America. The other type of three phase power distribution is called the WYE style.

Delta Channel

In T-carrier/ISDN communications, a delta channel/"D channel" contains signaling and status information.

Delta Frame

Also called Difference Frame. Contains only the pixels different from the preceding Key Frame. Delta frames reduce the overall size of the video clip to be stored on disk or transmitted on phone lines.

Delta Modulation

A method for converting analog voice to digital form for transmission. It is the second most common method of digitizing voice after Pulse Code Modulation, PCM. Sampling is done in all conversions of analog voice to digital signals. The method of sampling is what distinguishes the various methods of digitization (Delta vs.' PCM, etc.). In delta modulation, the voice signal is scanned 32,000 times a second, and a reading is taken to see if the latest value is greater or less than it was at the previous scan. If it's greater, a "1" is sent. If it's smaller, a "0" is sent.

Delta modulation's sampling rate of 32,000 times a second is four times faster than PCM. But delta records its samples as a zero (0) or a one (1), while PCM takes an 8-bit sample. Thus PCM encodes voice into 64,000 bits per second, while delta codes it into 32,000. Because delta has fewer bits, it could theoretically produce a poorer representation of the voice. In actual fact, the human ear can't hear the difference between a PCM and a Delta encoded voice conversation.

Delta modulation has much to recommend it, especially its use of fewer bits. Unfortunately no two delta modulation schemes are compatible with each other. So to get one delta-mod digital PBX to speak to another, you have to convert the voice signals back to analog. With AT&T making T-1 a de facto digital encoding scheme, PCM has become the de facto standard for digitally encoding voice. And although there are three types of PCM in general use, they can be made compatible on a direct digital basis (i.e. without having to go back to analog voice). One problem with PCM is that American manufacturers typically put twenty four 64,000 bit per second voice conversations on a channel and call it T-1. The Europeans put 30 conversations on their equivalent transmission path. Thus, you can't directly interface the American and the European systems. But there are "black boxes" available...(In this business, there are always black boxes available.)


The changes.

Delta Sigma Modulation

A variant of delta modulation in which the integral of the input signal is encoded rather than the signal itself. A normal delta modulation encoder by an integrating network. See Delta Modulation.

Delta Technology

An Internet access term. Delta technology consists of specialized remote adaptive routing protocols for optimizing bandwidth. It prevents unnecessary traffic from being sent over slow WAN connections by only sending the changes (deltas).


Coming out of online "lurking mode," usually motivated by an irresistible need to flame about something. "I just had to delurk and add my two cents to that conversation about a woman 's right to abortion."

Deluxe Queuing

A feature that allows incoming calls from phone users, tie trunks and attendants to be placed in a queue when all routes for completing a particular call are busy. The queue can be either a Ringback Queue (RBQ) ” the user hangs up and is called back when a trunk becomes available ” or an Off-Hook Queue (OHQ) ” the user waits off-hook and is connected to the next available trunk. Deluxe Queuing is a term used mainly by AT&T. Most modern PBXs have this feature. Most have simpler names, however.

Demand And Facility Chart

D&F. A telephone company definition. A chart designed to:

  1. Record an up-to-date picture of working network access lines, actual usage rates, future gains in working network access lines, and future usage rates.

  2. Record the capacity of existing equipment and the current picture of the planned capacity additions.

  3. Provide a recording vehicle to report consistent data (using standardized terminology and definitions) for planning, and budget review evaluation purposes.

Demand Assigned Multiple Access


Demand Assignment

A technique where users share a communications channel. A user needing to communicate with another user on the network activates the required circuit. Upon completion of the call, the circuit is deactivated and the capacity is available for other users.

Demand Factor

The ratio of the maximum demand on a power system to the total connected load of the system.

Demand Load

In general, the total power required by a facility. The demand load is the sum of the operational load (including any tactical load) and non-operational demand loads. It is determined by applying the proper demand factor to each of the connected loads and a diversity factor to the sum total.

Demand Paging

The common implementation in a PC of virtual memory, where pages of data are read into memory from storage in response to page faults.

Demand Priority

Access method providing support for time sensitive applications such as video and multimedia as part of the proposed 100BaseVG standard offering 100Mbit/s over voice grade UTP (Unshielded Twisted Pair) cable. By managing and allocating access to the network centrally , at a hub rather than from individual workstations, sufficient bandwidth for the particular application is guaranteed on demand. Users, say its proponents, can be assured of reliable, continuous transmission of information.

Demand Publishing

The production of just the number of printed documents you need at the present time, as in "just in time." In short, the immediate production of printed documents which have been created and stored electronically .

Demand Service

In ISDN applications, a telecommunications service that establishes an immediate communication path in response to a user request made through user- network signaling.


Pronounced D-Marc. The demarcation point is the physical point at which the separation is made between the carrier's responsibilities for the circuit and those of the end user organization. The carrier is responsible for the local loop, which connects the user organization's premises to the carrier's CO (Central Office) or POP (Point of Presence) at the edge of the network. In a residential or small business application, the demarc is at the NIU (Network Interface Unit), which typically is on the side of the house or inside the garage. In a larger business application, it is at the MPOE (Minimum Point of Entry), which is the closest practical point to where the carrier facilities cross the property line or the closest practical point to where the carrier cabling enters a building. While the MPOE typically is in the form of a physical demarc, in older installations it may simply be in form of a tag hung on the entrance cable to identify a point of logical demarcation. There are exceptions. In some older Centrex installations in some states, the demarc is at the jack for each individual voice or data terminal. In some older campus environments, there may be a demarc for each of several cables coming from various directions, and the demarcs may be well inside the property line. In either case, it is the responsibility of the carrier to install and maintain the local loop and the demarc device, which includes some form of protector against lightening and other electrical anomalies, and some form of intelligence to support loopback testing. It is the responsibility of the end user organization or building owner to install and maintain the inside cable and wire system, which typically terminates in the demarc through a plug-and-jack arrangement. A demarc for voice services might be in the form of a simple RJ-11C jack (one line or trunk) connection, an RJ-14C (two trunks), an RJ-21X (up to 25 trunks), or a 66-block. A demarc for data services typically supports an RJ-48 termination. See also Smart Jack.


An incorrect spelling of Demarc. See Demarc.

Demarcation Point

The point of a demarcation and/or interconnection between telephone company communications facilities and terminal equipment, protective apparatus, or wiring at a subscriber's premises. Carrier-installed facilities at or constituting the demarcation point consist of a wire or a jack conforming to Subpart F of Part 68 of the FCC Rules. See Demarc.

Demarcation Strip

The terminal strip or block (typically a 66 block) which is the physical interface between the phone company's lines and the lines going directly to your own phone system. See also Demarc.

Demilitarized Zone

DMZ. See DMZ and Screened Subnet.


Denmark Elektriske MaterielKOntrol (Denmark Testing Laboratory).

Democratically Synchronized Network

A mutually synchronized network in which all clocks in the network are of equal status and exert equal amounts of control on the others.


Demodulation/Remodulation. See Fax Relay.


The process of retrieving an electrical signal from a carrier signal or wave. The reverse of modulation. See Modem.

Demodulation Dial Tone Digital

The process of retrieving data from a modulated signal. A tone indicating that automatic switching equipment is ready to receive dial signals. Refers to the use of digits to formulate and solve problems or to encode information.


In general, this term refers to any device which recovers the original signal after it has modulated a high frequency carrier. In television, it may refer to an instrument which takes video in its transmitted form (modulated picture carrier) and converts it to baseband.

Demon Dialer

See Automatic Recall.

Demountable Walls

Metal walls that can be disassembled and moved to other locations. They contain vertical and horizontal slots through which cable can be run, also called modular panels.


DEMUX. To separate two or more signals previously combined by compatible multiplexing equipment. As an ATM term, it is a function performed by a layer entity that identifies and separates SDUs from a single connection to more than one connection.


A device that pulls several streams of data out of a bigger, fatter or faster stream of data.


A process applied to a multiplex signal for recovering signals combined within it and for restoring the distinct individual channels of the signals.


Jargon for demultiplexer.


Directory Enabled Network. DEN is designed to integrate network hardware with directory services, such as Novell's Directory Services or Microsoft's Active Directory. DEN is designed as an extension to the Desktop Management Task Force's (DMTF's) Common Information Model (CIM). The DEN specification is under development by the Desktop Management Task Force (DMTF). It includes a standard approach to defining schema for integrating network equipment, such as switches and routers, with a directory service.


The Danish Ethernet Network which consists of many Ethernet networks in universities connected together by bridges.

Denial of Business.

DoB. See Impact Analysis.

Denial Of Service

You're no longer allowed to use a service. That service might be anything from normal phone service (you didn't pay your bills) to not being allowed into the company's email because you were just fired . See also Denial of Service Attack.

Denial of Service Attack

You're a horrid person with mean intentions. You ping a website 400 or 500 times a second. Or, even worse , you create a virus and use e-mail attachments to infect a lot of networked computers, which become Zombies under your control. You command them all to go to that website, which is then overwhelmed and no longer able to serve its legitimate customers. In other words, your attack has the effect of denying service to the customers. Hence the term Denial of Service Attack. Such an attack is very hard to prevent, since sometimes it's done from computers all over the country or the world. This is called a Distributed Denial of Service Attack, or DDoS. InfoWorld Magazine of June 11, 2001 reported "to orchestrate DDoS assaults, a hacker first installs "cable bots" on computers that have cable or other high-speed modems, but that lack adequate firewalls against intrusion. These bots are then instructed to send massive amounts of data to a victim's site. Steve Gibson (president of Gibson Research Corporation) found that bots running on just 474 Windows PCs worldwide were enough to completely overwhelm his two T-1 lines."

According to Alcatel, the prevention of Denial of Service attacks requires five key components: 1) Upgrade. Many types of DoS attacks become useless as the vulnerabilities they leverage are detected and fixed. However, if a system still uses an older version of an application, certain vulnerabilities may still be available to attackers. One of the best prevention methods is to keep computer systems updated with the latest versions of the operating system and applications. It's also important to keep track of security updates/patches and make sure they are applied to all vulnerable systems. 2) Use a firewall. Firewalls can help prevent attacks by blocking unauthorized users and filtering packets to keep unwanted traffic out of the network. 3) Intrusion detection. Denial of Service attacks can occur without an obvious sign. Intrusion detection tools help monitor the network and detect the signs of different attacks, allowing you to identify and deal with attackers and harden the network against future attacks. 4) Virus protection. Denial of Service attacks are often propagated by worms, viruses, and Trojan horses that plant small programs on your system. These programs are designed to disrupt services, crash computers, or burden network connections. Current virus scanning products can help identify and remove infected files, as well as prevent future infections. 5) Diligence. It is important to keep up to date on current alerts, warnings, and security techniques. Organizations like the CERT Coordination Center and the Computer Incident Advisory Capability (CIAC) publish regular updates advising the computing community on current security threats and new technologies and information that can help system administrators make their networks more secure. See also Active Attack, Passive Attack, Smurf Attack, Spoofing, Trojan Horse, Virus, Worm and Zombie.

Denis The Little

The 6th century monk who decided that history should be split between B.C. and A.D. and inadvertently created the Y2K problem. See Y2K.


A low life citizen of the Internet. Not a complimentary term.

Dense Virtual Routed Networking

DVRN. This is the ultimate IP networking fantasy ” a network where bandwidth is unlimited and free, speed is not even taken into consideration, IP will never again bump heads with routers and their static routing tables, and data moves through "virtual routers" which will perform tasks way beyond today's elementary "connect the dot" computations . It's almost impossible to imagine such a stress free network with practically no limitations, but advances such as Dense Wave Division Multiplexing (DWDM), which advanced fibre optic transport by creating "virtual strands" used to carry multiple wavelengths of light multiplexed together gives us a sign of hope. All the above from the November 2000 of Computer Technology Review.

Dense Wavelength Division Multiplexing



  1. The number of bits (or bytes) in a defined length on a magnetic medium. Density describes the amount of data that can be stored.

  2. The number of circuits that can be packed into an integrated circuit.

  3. In a facsimile system, a measure of the light transmission or reflection properties of an area, expressed by the logarithm of the ratio of incident to transmitted or reflected light flux.


Japanese for telephone. An aka denwa is a red telephone. Some coin phones in Japan are red and are often known as aka denwas.

Departmental Firewall

The NEC PrivateNet Systems Group issued a White Paper called Connecting Safely to the Internet ” A study in Proxy-Based Firewall Technology. In that White Paper, they defined a Departmental Firewall:

A departmental firewall is identical to an Internet firewall except that it controls access to and from a single department in a larger organization. It is used to protect sensitive corporate data, such as financial information and personnel records, from access by unauthorized people. A departmental firewall tends to be more generous in the access it allows, but if insecure services, such as NFS (Network File System), are allowed through a departmental firewall, the purpose of installing the firewall in the first place might be defeated. See Firewall and NFS.

Departmental LAN

A local-area network used by a relatively small group of people working on common tasks; it provides shared local resources, such as printers, data, and applications.

Departure Angle

The angle between the axis of the main lobe of an antenna pattern and the horizontal plane at the transmitting antenna.


In 1879 a flu epidemic in Lowell, MA made it likely that all four of the telephone operators would get sick simultaneously . To help substitute operators, management numbered each of the exchange's two hundred plus customers. No problem. The customers accepted the change easily.


Getting off a plane. See Detraining.


  1. In electromagnetic wave propagation, that condition wherein a polarized transmission being transmitted through a nonhomogeneous medium has its polarization reduced or randomized by the effects of the medium being traversed.

  2. Prevention of polarization in an electric cell or battery.


A technique to reduce the traffic load on a switch by removing devices from the shelf or cabinet. Depopulating reduces the effective device capacity of a switch but can increase switching capacity. This is a ploy used to give older PBX systems traffic capacity nearer true ACD systems.

Depressed Cladding Fiber

An optical fiber construction, usually single mode, that has double cladding, the outer cladding having an index of refraction intermediate between the core and the inner cladding.


A cellular radio term. In the CDPD network, the process of dissociating an Network Entity Identifier (NEI) from the CDPD network.


The removal of regulatory authority to control certain activities of entrenched telephone companies. An attempt by federal authorities to make the telephone industry more competitive. Deregulation is meant to benefit the consumer. Sometimes it does. Sometimes it doesn't. Often, it's a scapegoat for whatever subsequently goes wrong. But it means different things in different countries. In some it means "a new company can come in and bash the living hell out of the local supplier," according to Philip Khoo, of Miller Freeman, Singapore. In other countries, it simply means giving the newcomers 5% of the market, while the old-timer keeps 95%.

Derivation Equipment

Equipment that produces narrowband facilities from a wider band facility. Such equipment can, for instance, derive telegraph grade lines from the unused portion of a voice circuit.

Derived Facilities

Transmission paths created by use of multiplexing methods that provide more than one virtual path per physical facility.

Derived MAC PDU

DMPDU. A Connectionless Broadband Data Service (CBDS) term that corresponds to the 1.2 PDU in Switched Multimegabit Data Service (SMDS). CBDC is the European equivalent of SMDS.


  1. Data Encryption Standard. A block cipher algorithm for encrypting (coding) data designed by the National Bureau of Standards so it is impossible for anyone without the decryption key to get the data back in unscrambled form. The DES standard enciphers and deciphers data using a 56-bit key specified in the Federal Information Processing Standard Publication 46, dated January 15, 1977. DES is not the most advanced system in computer security and there are possible problems with its use. Proprietary encryption schemes are also available. Some of these are more modern and more secure. The quality of your data security is typically a function of how much money you spend . See Block Cipher, Clipper Chip and NSA.

  2. Destination End Station: An ATM termination point which is the destination for ATM messages of a connection and is used as a reference point for ABR services. See SES.


Those parts (or tails ) of the letters p, y, j and g which descend below the base line. This type style is much easier to read than one in which the tails rest on the base line. Watch out for true (i.e. real) descenders when you're buying a system. Most have them these days, but many telephone screens don't. Careful.


A device which corrects a signal (often video) that has been intentionally distorted to prevent unauthorized viewing. Used with satellite TV systems. See DES.

DESI Strip

A slang term for Designation Strip, the small printed piece of paper or card that slides into or attaches onto a telephone and tells you which button answers which line or which button does what in the way of features or intercom.

Design Layout Report

DLR. A record containing the technical information that describes the facilities and terminations provided by a local telephone company to a long distance telephone company. The technical information is needed by the long distance carrier to design the overall service and includes such items as cable makeup (gauge, loading, length, etc.), carrier channel bank type and system mileage, signaling termination compatibility, etc. The DLR is sent to the designated carrier representative via the local telephone company's engineering department.

Designated Entities

See DE.

Designated Router

OSPF router that generates LSAs for a multiaccess network and has other special responsibilities in running OSPF. Each multiaccess OSPF network that has at least two attached routers has a designated router that is elected by the OSPF Hello protocol. The designated router enables a reduction in the number of adjacencies required on a multiaccess network, which in turn reduces the amount of routing protocol traffic and the size of the topological database.

Designation Strip

Also called Desi Strip. A Designation Strip is the small printed piece of paper that slides into or attaches onto a telephone and tells you which button answers which line or which button does what in the way of features or intercom.

Designing Around

Designing around is a legal process which deals with designing a new patent around an existing patent. This process often yields a better product than the patented device or method. Designing around is a perfectly legal operation. It has only been recognized and sanctioned by the courts for about 5 or 6 years . Most engineers and business owners are completely unaware of this option and think it sounds illegal when described to them. Designing around can be used to protect an existing patent or to file for a new one.


An imaging term. Adjusting ” straightening ” an image in software to compensate for a crooked scan.


The computer's working environment. The screen layout, the menu bar, and the program icons associated with the machine's operating environment. Apple's Macintosh (introduced on January 24, 1984) really started the idea that the computer's screen was a desktop. With Windows, PCs now also have desktops.

Desktop Collaboration

Using ISDN lines or analog lines with high speed lines, you can link your desktop computers so teleworkers, suppliers and clients can share documents and work together no matter where they are.

Desktop Connection

AT&T's code name for hardware which includes an AT&T serial port adapter, DSS cable and a 9 to 25 pin connector and some software to make it work. The new name for desktop connection is PassageWay. It attaches to the back of the AT&T phone. The cable connects the adapter to your PC's serial port. In AT&T's words, the AT&T PassageWay integrates telephone functions with a Microsoft Windows 3.1 or greater application, facilitating outdialing using the Hayes Command Set used by modems, linking caller identification to PC business applications, and paving the way to an open interface between the PC software and the telephone. As a development platform, AT&T PassageWay offers an application layer access to features of the telephone including receiving information on visual/audible alerts and telephone displays, activating button presses, turning the speakerphone on or off, adjusting the volume of the telephone and dialing, including some call state progress. In addition, operating with Windows provides a unique way of accessing and sharing information between applications that co-reside on a PC. Windows provides a Graphical User Interface (GUI) that allows software packages to be easily developed. Windows also offers the Dynamic Data Exchange (DDE) interface between co-resident applications that is a standard for sharing information on DOS PCs. AT&T PassageWay also passes information using Microsoft's DDE standard. See also AT&T Applications Partner.

Desktop Management Software

Desktop management software are products that perform software distribution, inventory and asset management, remote control an remote access capabilities. In other words, let's say that you're the IT manager of a big company and your says "By lunchtime tomorrow we need this new corporate software on 1800 desktops, 350 laptops and 890 PDAs. and we want everybody to have the same software." Desktop management software is what you need to give your company a consistent desktop configuration. Your boss wants a standard configuration because it saves a enormous number of tech support calls.

Desktop Management Task Force

A consortium of vendors working toward a set of standards for network management software which will ease the management of desktop systems, their components, and peripherals. Activities address "standard groups" such as software, PC systems, servers, monitors , network interface cards (NICs), printers, mass storage devices, and mobile technologies. The most notable of its accomplishments is the development of the Desktop Management Interface (DMI). See also DMI.

Desktop Metaphor

A desktop metaphor is the conceptual way a workstation screen area is used to emulate a user's physical desktop through graphic icon images. The icon maps directly to its real life function. For example, a trash can icon will allow a user to "throw out" a document. Gives an application a "user friendly" feel. Desktop metaphors are consistent throughout all Windows and windows-like applications, like Sparc's Open Look.

Desktop Nazi

An IT person who overcontrols the company's computing resources ” especially what you're allowed to run and not allowed on your own PC.

Desktop Pattern

A Windows 3.1 term. A design that appears across the desktop. You can use Control Panel to create your own pattern or choose a pattern provided by Windows.

Desktop Replacement

A full featured laptop that is powerful and has a fast microprocessor, a large display, full- sized keyboard, and a large hard drive and is considered to be a replacement for a desktop PC. Desktop replacements are typically heavier and larger than the average laptop. When you measure a desktop's performance next to a laptop's performance, you'll typically find the desktop to be much faster ” even though they may have the same CPUs, same memory, etc.

Desktop Video

Communications that rely either on video phones or personal computers offering a video window.

Desktop Videoconferencing

By combining ISDN technology and individual PCs, people can meet "face-to-face" without leaving their offices. It's a way to reduce costly and time-consuming travel, maybe.


To automatically generate a large amount of garbage to the 'Net, especially from an automated posting program gone wild.


The orientation of a satellite antenna, which keeps it pointed to the earth. Also used to refer to the communications payload section of a Hughes spinning satellite.

Despun Antenna

Of a rotating communications satellite, an antenna, the direction of whose main beam with respect to the satellite is continually adjusted so that it illuminates a given area on the surface of the Earth, i.e., the footprint does not move.


In systems that employ cache memory, destaging is the operation that reads data from magnetic disks and writes it to cache memory. "Destaging" occurs when data being removed from the cache to make room for new data has changed; it refers to the movement of changed data from cache back to disk.

Destination Address

That part of a message which indicates for whom the message is intended. Usually a collection of characters or bits. Just like putting a destination address on an envelope. On a token ring network this is a 48-bit sequence that uniquely defines the physical name of the computer to which a LAN data packet is being sent. The IEEE assures that in the world of LANs no two devices have the same physical address. It does so by assigning certain numbers to vendors of token ring adapters, the devices that connect computers to a token ring network.

Destination Address Filtering

A feature of bridges that allows only those messages intended for the extended LAN to be forwarded.

Destination Code

See Destination Field.

Destination Document

The document into which an object is linked or embedded via OLE. The destination document is sometimes also called the container document.

Destination Field

  1. A telephone company definition. A combination of digits that provides a complete address to reach a destination in the message network. Most destination codes are made up of some of the following components: Access Code, Area (NPA) Code, End Office Code (NNX), Main Station Number, Service Code, Toll Center Code.

  2. A networking term. The field in a message header that contains the network address of the individual for whom the message is meant and who will (with luck and good management) receive the message.

Destination Host

A computer system on the network that is the final destination for a file transfer or for an e-mail message.

Destination Node

Those system nodes which receive messages over the control packet network from the source or transmitting node.

Destination Point Code

DPC. The part of a routing label that identifies where the SS7 signaling message should be sent. See also Point Code.

Destination Service Access Point

DSAP. The logical address of the specific service entity to which data must be delivered when it arrives at its destination. This information may be built into the data field of an IEEE 802.3 transmission frame.


The controlled deletion of stuffing bits from a stuffed digital signal, to recover the original signal.


  1. In a radio receiver, a circuit or device which converts or rectifies high frequency oscillations into a pulsating direct current or which translates radio frequency power into a form suitable for the operation of an indicator. This is most frequently a vacuum tube, less commonly a crystal. Coherers and delicate chemical rectifiers were used in former years.

  2. In an optical communications receiver, a device that converts the received optical signal to another form. Currently, this conversion is from optical to electrical power; however, optical-to-optical techniques are under development.


An opto-electronic transducer that combines the function of an optical detector and emitter in a single device or module. Do not confuse with DTERM, a name for one of NEC's telephones that works on its NEAX 2000 and 2400 PBXs.

Detent Tuner

Click type of TV tuner.


The Cyber Defense Technology Experimental Research Network (DETER) is a model of the Internet built specifically to test its vulnerability to hackers, viruses, worms, trojan horses, denial of service attacks and other threats to its survival.


A verb that is part of the the internationally accepted way of finalizing and agreeing upon standards. For a full explanation, see ADSL Lite.

Deterministic Load Distribution

A technique for distributing traffic between two bridges across a circuit group. Guarantees packet ordering between source- destination pairs and always forwards traffic for a source-destination pair on the same segment in a circuit group for a given circuit-group configuration.


Difficulty in gaining access to the information highway. Often involves a Highway Construction Supervisor solving your access problem.


Getting off a train. An absolutely ghastly word invented by the railroad industry to keep them on a par with new, awful language invented by the airline industry. See also Deplaning, an equally awful word.

Device Contention

  1. Occurs when more than one application is trying to use the same device, such as a modem or printer. Some of the newer operating systems do a better job handling device contention.

  2. The way Windows 95 allocates access to peripheral devices, such as a modem or a printer, when more than one application is trying to use the same device.

Device Control

A multimedia definition. Device control enables you to control different media devices over the network through software. The media devices include VCRs, laser disc players, video cameras , CD players, and so on. Control capabilities are available on the workstation through a graphical user interface. They are similar to the controls on the device itself, such as play, record, reverse, eject, and fast forward. Device control is important because it enables you to control video and audio remotely ” without requiring physical access.

Device Discovery

The mechanism to request and receive the Bluetooth address, clock, class of device, used page scan mode, and names of devices. See Bluetooth.

Device Driver

A device driver acts as a translator between the device and software that is trying to use the device. Think of a printer attached to your PC. You type "A." You want it to print as an A. Your word processing software sends the "A" to software called a device driver, which translates it into bits the printer understands. A more formal explanation: A device driver is a special type of software (which may or may not be embedded in firmware) that controls devices attached to the computer, such as a printer, a scanner, a voice card, a diskette drive, a CD-ROM, a DVD-drive, a hard disk, monitor or mouse. A device driver is software that expands an operating system's ability to work with peripherals. A device driver controls the software routines that make the peripherals work. There are device drivers in virtually everything electronic today ” including all types of Walkmen, automobile windows, etc.

2. A program that enables a specific piece of hardware (device) to communicate with Windows 95. Although a device may be installed on your computer, Windows 95 cannot recognize the device until you have installed and configured the appropriate driver.

Device ID

A Plug and Play term. A code in a device's Plug and Play extension that indicates the type of device it is. The device ID and the vendor ID create a unique identifier for each PnP (Plug N Play) device.

Device Layer

The group of protocols that handles the hardware in a Bluetooth device. The device layer handles components such as the display, keypad, and RF communications.

Device Management Protocol

See DMP.

Device Rendering

Most sites are written for, and tested exclusively on desktop computers with large color monitors. Mobile wireless devices typically have much smaller screens, and until today, it has been a challenge to present Java and Web based enabled pages on these. Device Rendering technology intelligently reformats the today's Web sites and Windows based applications to fit inside the screen width, thereby eliminating the need for horizontal scrolling.


Doped Fiber Amplifier. An amplifier used in fiber optic systems to amplify light pulses. Such amplifiers typically are known as EDFAs (Erbium-Doped Fiber Amplifiers ) as they are doped with erbium, a rare-earth element. DFAs are more effective than regenerative repeaters in many applications, as they simply amplify the light pulses through a chemo- optical process. Regenerative repeaters, on the other hand, require that the light signal be converted to an electrical signal, amplified, and then re-converted to an optical signal. Additionally, DFAs can simultaneously amplify multiple wavelengths of light in a Wavelength Division Multiplex (WDM) fiber system. See also EDFA, SONET and WDM.


Distributed Feedback Laser. A type of laser used in fiber-optic transmission systems, at the distribution level of the local loop. DFBs are point-to-point lasers distributed among nodes in a geographic area such a neighborhood. They transmit and receive optical signals between the distributed nodes and the centralized node, where the signals are multiplexed over a higher-speed fiber link to the head-end (point of signal origin). DFBs can be more effective than the traditional approach of using a single laser which serves multiple nodes through a broadcast approach, as the available bandwidth can be segmented. DFBs have application in a FTTN (Fiber-To-The-Neighborhood) local loop scenario. See also FTTN and SONET.


Digital Facility Interface. An 5ESS switch circuitry in a DTLU responsible for terminating a single digital facility and generating one PIDB (Peripheral Interface Data Bus).


Dynamic Frequency Selection. See 802.11a.


Direct Facility Termination. A telephone company trunk that terminates directly on one or more telephones.


Directorate General (CEC).


Dynamic Gain Equalizer. See Dynamic Gain Equalizer.


Differential Global Positioning Service ” a new venture of the US Coast Guard, which it hopes to have ready by 1996. It will use an existing network of radio beacons throughout the US to create a fixed grid of known reference points in order to improve the accuracy of the Defense Department's GPS signal. The Coast Guard hopes to achieve an accuracy of about 10 meters .


Direccion General de Telecommunicaciones (Spanish General Directorate of Telecommunications).


Dynamic Host Automatic Configuration Protocol. See DHCP.


Dynamic Host Configuration Protocol. DHCP is a TCP/IP protocol that enables PCs and workstations to get temporary or permanent IP addresses (out of a pool) from centrally-administered servers. The host computer runs the DHCP server, and the workstation runs the DHCP client. DHCP allows a server to dynamically assign IP addresses to nodes (workstations) on the fly. Like its predecessor, The Bootstrap Protocol (Bootp), DHCP supports manual, automatic and dynamic address assignment; provides client information including the subnetwork mask, gateway address, and DNS (Domain Address Server) addresses; and is routable. DHCP offers the advantage of automatic configuration, whereas Bootp must be configured manually. A DHCP server, generally in the form of a dedicated server, verifies the device's identity, "leases" it the IP address for a predetermined period of time, and reclaims the address for reassignment at the expiration of that period. DHCP relieves the pressure on the current IPv4 numbering scheme; the emergence of IPv6, with its expanded numbering scheme, may obviate DHCP. See also BOOTP and IPv6.


Benchmark program for testing the speed of a computer. It tests a general mix of instructions. The results in Dhrystones per second are the number of times the program can be executed in one second. The Dhrystone benchmark program is used as a standard indicating aspects of a computer system's performance in areas other than its floating-point performance, for instance, integer processes per second, enumeration, record and pointer manipulation. Since the program does not use any floating-point operations, performs no I/O, and makes no operating system calls, it is most applicable to measuring the performance of systems programming applications. The program was developed in 1984 and was originally written in Ada, although the C and PASCAL versions became more popular by 1989. See Whetstones.


Direct to Home satellite TV.


Abbreviations for Dispatch In (inside technicians), Dispatch Out (outside field technicians).


Document Interchange Architecture/Document Content Architecture. IBM promulgated architectures, part of SNA, for transmission and storage of documents over networks, whether text, data, voice or video. Becoming industry standards by default.

Diablo Wind

As explained in Jim Carlton's excellent book, "Apple, the Inside Story of Intrique, Egomani and Business Blunders:" Infrequently a heat wave bakes the entire San Francisco Bay area including Silicon Valley, when the high pressure system that is usually parked over the Pacific and is responsible for generating those delicious marine breezes shifts over to nearby Nevada and funnels hot, dry air down that same mountain range in a reverse flow. The effect is known locally as a "Diablo wind," because the range these pour down is called the Diablo. "Diablo" is a Spanish word meaning "devil," so these are devil winds and appropriately named because they can spark wicked firestorms that wreak destruction and havoc across the region.

Diagnostic Programs

Programs run by the computer portion of a PBX to detect faults in the system. Such programs may run automatically at regular intervals or continuously. The goal of diagnostic programs is to detect faults before they become serious and to alert someone ” typically the attendant ” to go fix it. Some diagnostic programs stop running when the switch gets too busy. Some don't. You can dial into some diagnostic programs from afar. You can't dial in remotely on some others. Remote diagnostic programs are among the greatest boons to improved reliability of telephone systems.


A term used in the secondary marketplace . Original Equipment's Manufacturer (OEM) prescribed test procedure whose successful completion is normally required for maintenance acceptance of a switch, cabinet, or peripheral piece of equipment. Comment: A new maintenance contract will not go into effect until the maintenance company accepts the results of the diagnostics.


A round face or display upon which some measurement is registered, usually in the form of graduations of values. Examples include sundials; analog watches and clocks; and analog speedometers, pressure gauges, and tachometers. In telecommunications, "dial" generally refers to dial telephones, which generally are considered to be obsolete. Dial telephones, for those of you who are relative youngsters and have never seen one, have a round dial on the face of the telephone set. The dial has finger holes which correspond to numbers on a faceplate. The numbers are 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0. To dial a number, you put your finger in the hole, and turn the dial clockwise until it stops. You then remove your finger, thereby allowing the dial to return to its original position. You do this successively until you have dialed the entire number. As the dial returns to its original position in each case, the telephone set mechanically opens and closes an electrical circuit, thereby pulsing the number to the central office switch. Dial telephone are very different from touchtone telephones, which have keypads, or tonepads. Dial telephones are very slow, and they wear out your finger. The actual "dial" on rotary dial phones is called the finger wheel. It's OK to say dial, even if you make your calls by tapping buttons on a touch- tone pad. Touch-Tone was originally a trademark of AT&T, but they let the trademark lapse. A maker of cheapie phones used Touch-Tone as a brand name in the mid-80s, but they seem to have disappeared. Most phones and phone systems can be switched to produce either touch-tones or dial pulses (clicks), like old rotary dial phones, for use with central offices that don't accept touch-tones. The technical term for touch-tone is DTMF (dualtone/multi-frequency). See also Dial Pulsing and DTMF.


DMS Integrated Access Local Area Network from Northern Telecom.

Dial A Prayer

A sarcastic name for the local 611 number run by the local telephone companies as their centralized number for repair.

Dial Around

A method used by callers to purposely bypass a payphone company's local or long distance carrier services. Such methods include calling cards and alternative carrier's collect services, such as 1-800-COLLECT or 1-800-CALL-ATT. Payphone operators receive little or no revenue from such calls.

Dial Backup

  1. A network scheme using dial-up phone lines as a replacement for failed leased data lines. In one typical case, two dial-up lines can be used. One dial-up link is used to transmit data and the other to receive data, thus giving us full-duplex data transmission.

  2. A security feature that ensures people do not log into modems that they shouldn't have access to. When a connection is requested , the system checks the username presented for validity, then "dials back" the number associated with that username.

Dial By Name

You can dial someone by spelling their name out on the touchtone pad. Typically, the system plays a recorded announcement giving directions for using the Dial by Name feature: the caller then inputs the appropriate digits/letters. When the system recognizes a match, a recorded announcement states the name of the dialed party for confirmation by the caller before automatically completing the call. If the input digits are not uniquely associated with a particular station the system may ask the caller to pick a name from a menu of choices. Dial by Name is getting cheaper. Automated attendants are being programmed to have the feature. And you shouldn't buy an auto attendant unless it has this feature.

Dial Call Pickup

A phone user on a PBX or hybrid can dial a special code and answer calls ringing on any other phone within his own predefined pickup group.

Dial Dictation Access

A service feature available with some switching systems that permits dialing a special number to access centralized dictation equipment.

Dial In Banner

An Internet Access Term. Optional pop-up window for dial-in connections. Allows network managers to display information or warning messages when users dial into remote networks.

Dial In Channel Aggregation

The ability to use more than one communications channel per connection. By aggregating both 64 kbit/s ISDN B channels, users can take advantage of 128 kilobits per second dial-in connections. Fast 128 kbit/s data transfer rates reduce large file transfer times. The same as Bonding.

Dial In Tie Trunk

A Dial In Tie trunk is a trunk that may be accessed by dialing an access code and then seizing a dedicated transmission path to a distant PBX (or another PBX a short distance away). Once the trunk is seized in the distant PBX, the caller may then use the features of that PBX, depending on the class-of-service and restrictions assigned to the trunk.

Dial It 900 Service

A special one-way mass calling service that allows prospects, customers and others to reach you from anywhere across the country. In contrast to 800- service, the caller pays the 900 charge, generally one charge for the first minute, with a lesser charge for each additional minute. DIAL-IT 900 Service is a great way to involve your customers and prospects in a promotion! Premium Billing lets you select a rate above standard DIAL-IT 900 rates. The long distance carriers (through their deals with local phone companies) handle the billing. You, the information provider, split the revenues with the long distance provider. International DIAL-IT 900 service is currently available from a growing number of countries.

Dial It Service

A telecommunications service that permits simultaneous calling by a large number of callers to a single telephone number. There is usually a fee for calls to 900 number or 976 numbers. See also Dial It 900 Service.

Dial Level

The selection of stations or services associated with a PBX, based on the first digit(s) dialed.

Dial Pacing

An element of Predictive Dialing. It is important to draw a distinction between the simple placement of the calls (dialing the numbers) versus the logic that goes into when calls are made and how many to make at the same time. These decisions are made automatically by pacing algorithm software. In effect, the computer telephony equipment is a slave to the pacing algorithm. The switch dutifully makes the calls that are requested under the control of this software. Pacing software is based on huge database records. These records include information on time of day, anticipated odds of the called party answering, the number of live agents that are available to take calls, the work schedule for the call center employees , etc. It is possible for a predictive dialing system to pace calls based on a canned algorithm. For example, the software may instruct the VRU to dial 25 calls a minute no matter what. This may be suitable if the need for operator transfer is not critical, or if the information to be delivered does not require operator intervention. See also Predictive Dialing.

Dial Pick-Up

PBX feature. A phone on a PBX can answer another ringing phone by dialing a few digits. Also called an access code.

Dial Pulse

DP. A type of switched access line address signaling that uses rapid loop open and loop closure signals (pulses) to indicate the digit being dialed. The digits 1 through 9 are represented by a defined number of pulses; the digit zero is represented by ten pulses.

Dial Pulse Signaling

A type of address signaling in which dial pulse is implemented to signal the distant equipment. See Dial Pulsing.

Dial Pulsing

A means of signaling consisting of regular momentary interruptions of a direct or alternating current at the sending end in which the number of interruptions corresponds to the value of the digit or character. In short, the old style of rotary dialing. Dial the number "five" and you'll hear five "clicks." See Dial Speed, Dial Train and DTMF.

Dial Repeating Trunks

PBX tie trunks used with terminating PBX equipment capable of handling telephone signaling without attendant involvement.

Dial Selective Signaling

A multipoint network in which the called party is selected by a prearranged dialing code; typified by the Bell SS-1 Selective Signaling System.

Dial Service Assistance

DSA. A service feature associated with the switching center equipment to provide operator services, such as information, intercepting, random conferencing, and precedence calling assistance.

Dial Speed

The number of pulses a rotary dial can send in a given period of time, typically 10 per second. A Hayes modem with a communications package, like Crosstalk, can send 20 pulses per second.

Dial String

A Dial String is the sequence of characters sent to a device which can dial a phone number. Such a device might be a modem or a voice processing card. Here are some "digits" in a dial string: ! ” flashhook (TAPI standard); & ” flashhook (Dialogic); T ” use tone dialing; , ” pause (typically of half a second to two seconds); W ” wait for dial tone.

Dial String/Command String

A sequence of characters and digits used for dial-in access; ATDT5107861000,,,,,,,,123456, H<CR> for example.

Dial Through

A technique, applicable to access circuits, that permits an outgoing routine call to be dialed by the PBX user after the PBX attendant has established the initial connection.

Dial Tone

The sound you hear when you pick up a telephone. Dial tone in North America is a unbroken signal between 350 Hz and 440 Hz that is generated by (i.e. sent from) your local telephone company. By hearing the dial tone, you know that your phone company is alive and ready to receive the number you dial. If you have a PBX, dial tone will typically be provided by the PBX. Dial tone does not come from God or the telephone instrument on your desk. It comes from the switch to which your phone is connected to. Outside North America, dial tone often sounds very different. And modems PCs, which are set up to "wait for dial tone" often don't recognize these unusual dial tones. The key then is a disable the modem's property that says "wait for dial tone," and have it begin dialing the second it goes off hook.

Dial Tone Delay

  1. The specific time that transpires between a subscriber's going off-hook and the receipt of dial tone from a servicing telephone central office. It's a measure of the time needed to provide dial tone to customers. Many of the local public service commissions in the United States say that 90% of customers should receive dial tone in fewer than three seconds.

  2. A telephone company definition. Percent Dial Tone Delay (% DTD) over three seconds is a measurement of calls that did not receive dial tone within three seconds. The average busy season objective for an entity in the busy season of exhaust is a maximum of 1.5 percent and is the engineering objective ceiling for all types of equipment. In addition the following maximum DTD engineering ceilings for an entity to be included in the equipment design:

    • Highest Annually Recurring Day ” Not over 20%. This maximum ceiling is to be applied to all types of offices.

    • Average 10 High Day ” Not over 8%. This maximum ceiling is to be applied in analog ESS offices.

Dial Tone First Coin Service

A type of pay phone service in which dial tone is received when the caller goes off-hook and coins must be inserted only after the call is connected.

Dial Tone Speed

DTS. A telephone company definition. The length of time required for switching equipment to provide dial tone to a subscriber originating a call. Usually expressed as the percentage of attempts that delayed over three seconds.

Dial Train

The series of pulses or tones sent from the phone that's calling and the switching system it's attached to in order to signify the call's destination.

Dial Up

The use of a dial or push button telephone to create a telephone or data call. Dial-up calls are usually billed by time of day, duration of call and distance traveled. A connection to the Internet, or any network, where a modem and a standard telephone are used to make a connection between computers. See Dial Up Line.

Dial Up Account

You want to access the Internet. You dial your local Internet Service Provider (ISP) via a local phone number. That's called a Dial Up Account. You can also have a dedicated account, which means that physically a piece of wire (and other electronics) connects you (i.e. your computer) to your ISP 24-hours a day, seven days a week. Mostly, dedicated is more expensive than dial up (depending on rates, etc.). But there are big advantages to dedicated ” including, faster access, getting your mail the instant it comes in, etc. See xDSL and Cable Modem.

Dial Up Line

A telephone line which is part of the switched nationwide telephone system. Typically a "dial up line" is a standard analog POTS line. These days, ISDN lines are dial up, also. So this definition is changing also.

Dial Up Modem

A modem that works on the public switched telephone network (PSTN) and connects to a remote computer resource for the duration of an individual call. See Modem.

Dial Up Networking

A Windows 95 and 98 definition. It is a service that provides remote networking for telecommuters, mobile workers, and system administrators who monitor and manage servers at multiple branch offices. Users with Dial-Up Networking on a computer running Windows 95 can dial in for remote access to their networks for services such as file and printer sharing, electronic mail, scheduling, and SQL database access.

Dial Zero Phone

A telephone on a Northern Telecom Norstar phone system which is assigned to ring when someone dials 0 (zero) from another Norstar telephone.


See Dial It Service.

Dialback Security

Dialback security is a telecom security feature. If a person calls in wanting remote access, the system asks for a password. Once it receives a correct password, it hangs up on the caller and dials back a pre-defined remote number, only then giving the caller access. Unless the hacker has you tied up in your living room, it makes things very secure. It can be made even more secure with multiple passwords and features like voice recognition.


To have your shit together; to have all the parts on your equipment working smoothly. As in "Hey, I finally got that bike dialed." Or, for indoorsy types, "Hey, I finally got that phone dialed."

Dialed Number Identification Service

See DNIS and 800 Service.

Dialed Number Recorder

Also called a Pen Register. An instrument that records telephone dial pulses as inked dashes on paper tape. A touchtone decoder performs the same thing for a touchtone telephone.


A standalone device which automatically dials a telephone number. Once upon a time (circa the 1960s), mechanical card dialers were invented to allow the automated dialing of numbers. These peripheral devices connected to a telephone set and made use of little plastic punch cards. You punched out little round holes in the card, with the holes corresponding to the number you dialed frequently, and you wrote the person's name on the card. When you wanted to dial the number, you inserted the card into the dialer, you punched the "start" button, and the dialer automatically dialed the number. Those early dialers saved a lot of wear and tear on your fingers. Dialers today are electronic devices which dial via tones, rather than dial pulses and who store their numbers in random access memory on chips, just like personal computers. Before the days of equal access and intraLATA long distance competition, dialers were used to "dial around" the LEC (Local Exchange Carrier), so that you could place cheaper intraLATA long distance calls. Today, you find dialers in airports. You find a phone with no keypad. You pick up the handset and the phone dials paging. Near to the luggage collection, you'll often find phones with many buttons. Each button may be for a particular hotel in the area. See also Dial.

Dialing Parity

Dialing parity is a technological capability that enables a telephone customer to route a call over the network of the customer's preselected local or long distance phone company without having to dial an access code of extra digits. Here's a more technical definition from the Telecommunications Act of 1996: The term "dialing parity" means that a person that is not an affiliate of a local exchange carrier is able to provide telecommunications services in such a manner that customers have the ability to route automatically, without the use of any access code, their telecommunications to the telecommunications services provider of the customer's designation from among 2 or more telecommunications services providers (including such local exchange carrier). See also Telecommunications Act of 1996.

Dialing Pattern

Dialing pattern refers to the digits you need to dial to place local, long distance, collect calls, or other phone calls. Dialing patterns will vary due to different types of telephone carrier switching equipment, computer software and the host carrier's credit policies (e.g. automatic roaming versus credit card roaming when using a cellular phone).

Dialing Plan

A description of the dialing arrangements for customer use on a network.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133 © 2008-2017.
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