Glossary - Definitions You Can Use

We don't try to drown you in technical talk. We want to make sure every part of your job is exactly the way you want it. Bookmark this helpful glossary to get definitions for terms that may appear in our proposals or our project documentation.

You will also see the definition for these words or phrases display throughout our website wherever the words or phrases are used in context.

# |  A - C |  D - K |  K - R |  S - Z
D Channel The D channel is a packet-switched channel that carries signaling and control for B channels. In Basic Rate ISDN (BRI) applications, it can also support customer packet data traffic at speeds up to 9.6 kilobits per second.
Daisy Chain In telecommunications, a wiring method where each telephone jack in a building is wired in series from the previous jack. Daisy chain is NOT the preferred wiring method, since a break in the wiring would disable all jacks “downstream” from the break. See also Home Run
Data Center A data center is a facility used for housing a large amount of electronic equipment, typically servers, computers, and communications equipment. Data centers are designed to assure that the servers and the data housed on them are protected from environmental hazards and security breaches. Data centers can be private, serving a single company or a public “utility” serving a variety of companies.
Data communication The movement of encoded information by means of electric transmission systems via one or more data links according to a protocol.
Data concentrator A unit that permits a common transmission medium to serve more data sources than there are channels currently available.
Data Communication Equipment (DCE) Devices and connections, such as printers or modems, of a communications network; connect the communication circuit between the data source and destination.
Data Local Exchange Carrier (DLEC) A carrier that primarily transports data with no voice grade services.
Data Service Unit or Digital Service Unit (DSU) Device that connects data terminal equipment (such as a personal computer or a LAN) to a digital telephone line to allow fully digital communications; in effect, the digital equivalent of a modem.
Data Terminal Equipment (DTE) Equipment/digital end instruments that convert user information into data signals for transmission, or reconvert the received data signals into user information.
Data transmission The sending of data from one place to another by means of signals over a channel.
Decibel (dB) The logarithmic unit of signal power ratio most commonly used in telephony. It is used to express the relationship between two signal powers, usually between two acoustic, electric, or optical signals.
Dedicated LAN Network segment allocated to a single device. Used in LAN switched network topologies.
Dedicated Line A communications circuit or channel provided for the exclusive use of a particular subscriber. Dedicated lines are used for computers when large amounts of data need to be moved between points. Also known as a private line.
Delay Skew The difference in propagation delay between the fastest and slowest pair in a cable or cabling system.
Demarcation Point The point of interconnection between telephone company terminal equipment and your building wiring. The protective apparatus or wiring at a subscriber’s premises.
DHCP DHCP (Dynamic Host Configuration Protocol) is a protocol that lets network administrators automate and centrally manage the assignment of Internet Protocol (IP) addresses in an organization's network. Using the Internet's set of protocols (TCP/IP), each machine that connects to the Internet needs a unique IP address. When an organization sets up its computer users with a connection to the Internet, an IP address must be assigned to each machine. Without DHCP, the IP address must be entered manually at each computer and, if computers move to another location in another part of the network, a new IP address must be entered.
Dielectric Nonmetallic and, therefore, nonconductive. Glass fibers are considered dielectric. A dielectric cable contains no metallic components.
Differential Mode Transmission A transmission scheme where voltages appear equal in magnitude and opposite in phase across a twisted-pair with respect to ground. May also be referred to as balanced mode.
Digital or Digitized Any type of information that can be output, transmitted and interpreted as individual bits of binary information (the use of the numbers 0 and 1), using electrical or electronmagnetic signals that can be modulated to convey their specific content.
Digital Signal 0 (DS0) A Special Access Service offering a 64 Kbps high-bandwidth dedicated circuit, that delivers quality that typically can't be duplicated with unconditioned analog circuits.
Digital Signal 1 (DS1) A Special Access Service that provides virtually error-free voice, video and data transmission at speeds up to 1.544 Mbps.
Digital Signal 3 (DS3) A Special Access Service comparable to having 672 voice-grade channels capable of handling multiple data streams in high volume at speeds up to 44.736 Mbps (commonly referred to as a 45 Megabit channel).
Digital Subscriber Line (DSL) A generic name for a group of enhanced speed digital services provided by telephone service providers. DSL services run on twisted-pair wires; they carry both voice and data.
Digital Switch A computer that electronically switches digitally encoded messages through the telephone network. Operates faster, more efficiently and more flexibly than an analog switch.
DIGITAL TELEVISION (DTV) A new technology for transmitting and receiving broadcast television signals. DTV provides clearer resolution and improved sound quality.
Digital Transmission A mode of transmission in which all information is transmitted in digital form as a serial stream of pulses. Sound waves and other information are converted into binary computer code (a series of 0s and 1s) and transmitted to the end point. At the end point, binary code is converted back into the original format. Digital transmission provides sharper, clearer, faster transmission than analog transmission.
Digital System Cross-Connect (DSX) Panel or Frame A bay or panel to which high-speed lines such as T-1 lines are attached. Used in small office applications where only a few digital trunks are installed, a DSX permits cross connections.
Dispersion A general term for those phenomena that cause a broadening or spreading of light as it propagates through an optical fiber. The three types are modal, material and waveguide.
Distribution duct A raceway of rectangular cross-section placed within or just below the finished floor and used to extend the wires or cables to a specific work station/area.
Distribution network Part of the local exchange cable network, comprising small cables between subscribers’ distribution points (DPs) and cabinets, remote line units (RLUs) or other flexibility points.
Distribution panel A rack mounted patch panel that terminates horizontal cabling from workstations.
Duct -1 A single enclosed raceway for wires or cables. See also raceway; 2. A single enclosed raceway for wires or cables usually used in soil or concrete; 3. An enclosure in which air is moved. Generally part of the HVAC system of a building.
DNS The domain name system (DNS) is the way that Internet domain names are located and translated into IP (Internet Protocol) addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.
Duplex Allowing communication in opposite directions simultaneously as in duplex telephony. Also a duplex receptacle wallplate, meaning it contains 2 outlets.
Duplex cable A two-fiber cable suitable for duplex transmission.
Duplex transmission Transmission in both directions, either one direction at a time (half duplex) or both directions simultaneously (full duplex).
Electronic Industries Alliance (EIA) A trade organization of manufacturers which set standards for use of its member companies. Many associations fall under the umbrella of EIA, though it has recently been absorbed by the TIA, or Telecommunications Industry Association.
EIA/TIA Electronics Industry Association/Telecommunications Industry Association
Electromagnetic Interference (EMI) The interference in signal transmission or reception caused by the radiation of electrical and magnetic fields.
Electromagnetic Compatibility (EMC) The ability of a system to minimize radiated emissions and maximize immunity from external noise sources.
Electromagnetic Interference (EMI) The interference in signal transmission or reception caused by the radiation of electrical and magnetic fields.
Electronic Commerce A set of services which enable the secure exchange of electronic funds via the internet. Generally, E-Commerce is referred to in relation to websites that promote products and services for immediate sale.
Electronic Data Interchange (EDI) Industry standard method of electronically exchanging data such as orders, invoices, etc. between two different locations or organizations.
Email (or E-Mail) An abbreviation for electronic mail, which is a network service that allows users to send and receive messages via computer. The Internet and common message protocols makes it possible to send and receive email messages worldwide.
EMI segregation Isolation of the telecommunications signal from electromagnetic interference.
Encryption key An alphanumeric (letters and/or numbers) series that enables data to be encrypted and then decrypted so it can be safely shared among members of a network. WEP uses an encryption key that automatically encrypts outgoing wireless data. On the receiving side, the same encryption key enables the computer to automatically decrypt the information so it can be read.
Enterprise Network A geographically dispersed network under the auspices of one organization.
Entrance Facility An entrance to a building for both public and private network service cables (including antennae), including the entrance point at the building wall and continuing to the entrance room or space. Entrance facilities are often used to house electrical protection equipment and connecting hardware for the transition between outdoor and indoor cable.
Entrance point (telecommunications) The point of emergence for telecommunications cabling through an exterior wall, a floor, or from a conduit.
Epoxy Connector A type of fiber optic connector that requires a chemical bond, or epoxy.
Equal Level Far-end Crosstalk (ELFEXT) Crosstalk measured at the opposite end from which the disturbing signal is transmitted, normalized by the attenuation contribution of the cable or cabling.
Equipment Cable A cable or cable assembly used to connect telecommunications equipment to horizontal or backbone cabling.
Equipment Room (ER) An Equipment Room is a centralized space that houses telecommunications equipment. ERs are generally considered to serve an entire building or campus, while TRs serve one floor of a building or a portion of a floor. An ER may contain active equipment, cross-connect facilities and building facilities (e.g. life safety, security, electrical and HVAC).
ESSID The identifying name of an 802.11 wireless network. When you specify your correct ESSID in your client setup you ensure that you connect to your wireless network rather than another network in range. (See SSID.) The ESSID can be called by different terms, such as Network Name, Preferred Network, SSID or Wireless LAN Service Area.
Ethernet Ethernet is the most widely installed local area network technology. Now specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.
Fan-out cable Multi-fiber cable constructed in the tight buffered design. Designed for ease on connectorization and rugged applications for intra-or inter-building requirements.
Far-end Crosstalk (FEXT) Crosstalk measured at the opposite end from which the disturbing signal is transmitted.
Fast Ethernet A 100-Mbps technology based on the 10BASE-T Ethernet CSMA/CDNetwork access method for operating local area networks (LAN).
FC Connector A type of optical fiber connector identifiable by its round, screw-operated locking nut. It is usually metal. Its ruggedness leads it to be widely used in test equipment
Federal Communications Commission (FCC) A federal government agency authorized by the Communications Act of 1934 to regulate interstate and international telecommunications originating in the United States. The FCC plays a role in implementing the Telecommunications Act of 1996.
Ferrule A component of a fiber optic connection that holds a fiber in place and aids in its alignment.
Fiber channel An ANSI standard designed to provide a standardized protocol and system-level interconnect, while being flexible and cost effective. It specifies several data rates up to12.75 Gb/s.
Fiber Distributed Data Interface (FDDI) Operates at 100 megabits per second (Mb/s). Developed by the ANSI X3T9.5 committee. This is a token-passing, dual-ring architecture that provides redundancy using fiber optic cable with transmission up to 2 kilometers.
Fiber Distribution Frame (FDF) Termination point in a central office where fiber optic cable is available to the switch.
Fiber Optics Communications technology that uses thin filaments of glass or other transparent materials. Fiber optic technology offers extremely high transmission speeds, allowing for data-intensive services such as video on demand.
Fiber optic attenuator A component that is installed in a fiber optic transmission system to reduce the power in the optical signal. It is often used to limit the optical power received by the photodetector to within the limits of the optical receiver.
Fiber optic communication system The transfer of modulated optical energy through optical fiber media which terminates in the same or different media.
Fiber optic link A combination of fiber optic spans and repeaters which are concatenated to form a transmission path. Fiber optic data link consists of an optical transmitter, optical fiber and an optical receiver. In addition, any splices or connectors used to join individual optical fiber sections to each other and to the trans¬mitter and the receiver are included.
Fiber Optic Test Procedure (FOTP) Standards developed and published by the Telecommunications Industry Association (TIA) under the TIA/EIA-455 or TIA-455 series of standards.
Fiber Optic Transmission A communications scheme whereby electrical data is converted to light energy and transmitted through optical fibers.
Fiber to the Building (FTTB) Fiber optic access to end user residence for telephone, video and other multimedia services, where several users share the same fiber termination. FTTB access typically terminates in a basement from which access to multiple end users is implemented through an in-building Digital Home Network (DHN).
Fiber to the Curb (FTTC) Fiber optic distribution of telephony, telecommunications, and multimedia and media services such as cable TV to a point outside the customer premise.
Fiber to the Home (FTTH) Fiber optic access to the end user residence for telephony, video and other multimedia services where each home has a direct fiber connection.
Fiber to the Premise (FTTP) Fiber optic distribution of telephony, telecommunications, and multimedia and media services such as cable TV to a point outside the customer premise.
Field In video, this is one vertical sweep of a raster scan. In 1:1, 2:1 and 4:1 interlaced video, one, two, and four fields respectively make up a video frame.
File Transfer Protocol (FTP) FTP (File Transfer Protocol), a standard protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their computer of origin to a publicly accessible computer server for everyone on the Internet. FTP is also commonly used to download programs and other files to your computer from other servers.
Firestop A material, device, or assembly of parts installed in a cable pathway at a fire-rated wall or floor to prevent passage of flame, smoke or gases through the rated barrier (e.g., between cubicles or separated rooms or spaces).
Floor Distributor (FD) The international term for horizontal cross-connect. The distributor used to connect between the horizontal cable and other cabling subsystems or equipment.
Footprint The area in which a specific transmission can be received. Some footprints, such as those of satellite or cell systems, cover as much as one-third of the earth.
Frame-Telecommunications A logical grouping of information sent as a link-layer unit over a transmission medium. The terms, packet, datagram, segment and message are also used to describe logical information groupings at various layers of the OSI Reference Model, and in various technology circles.
Frame-Video Applications A frame is a complete video picture. In the 2:1 interlaced scanning format of the RS-170 and CCIR formats, a frame is made up of two separate fields of 262.5 or 312.5 lines interlaced at 60 or 50 Hz to form a complete frame which appears at 30 or 25 Hz. In video cameras with a progressive scan, each frame is scanned line-by-line and not interlaced; most are also presented at 30 and 25 Hz.
Frame Relay High-performance interface or packet-switched networks. Considered more efficient than X.25 (which it is expected to replace). Frame relay technology can handle "bursty" communications that have rapidly changing bandwidth requirements.
FTP (Foiled Twisted Pair) is balanced twisted pair cable with an overall foil shield and drain wire. Also called screened twisted pair (ScTP) cable.
F/UTP (Overall foiled screened with unshielded twisted pairs). See FTP. Gigabit When used to describe data transfer rates, it refers to 10 to the 9th power (1,000,000,000) bits. Gigabit Ethernet, abbreviated GbE, supports data transfer rates of 1 Gigabit (1,000 megabits) per second. The first Gigabit Ethernet standard (802.3z) was ratified by the IEEE 802.3 Committee in 1998.
Fusion splicing A permanent joint accomplished through the application of localized heat sufficient to fuse the ends of the optical fiber, forming a continuous single fiber.
Gateway The entrance and exit to a communications network or system; a device or set of functions that facilitate electronic access by users to remote services or systems and vice versa. In data networks, gateways are typically a network node that connects otherwise incompatible networks. Gateways are commonly used to connect computers on one network, say a token-ring network, with those on a long-distance network. A gateway may be used to interface between two incompatible electronic mail systems or for transferring files from one system to another.
Graphical Interchange Format (GIF) A GIF is one of the two most common file formats for graphic images on the World Wide Web. On the Web and elsewhere on the Internet (for example, bulletin board services), GIF has become a de facto standard image format. Technically, a GIF uses the 2D raster data type, is encoded in binary, and uses LZW compression. There are two versions of the format, 87a and 89a. Version 89a (July, 1989) allows for the possibility of an animated GIF, which is a short sequence of images within a single GIF file. A GIF89a can also be specified for interlaced presentation.
Gigabit When used to describe data transfer rates, it refers to 10 to the 9th power (1,000,000,000) bits. Gigabit Ethernet, abbreviated GbE,supports data transfer rates of 1 Gigabit (1,000 megabits) per second. The first Gigabit Ethernet standard (802.3z) was ratified by the IEEE 802.3 Committee in 1998.
Graded-index fiber An optical fiber whose core has a non-uniform index of refraction. The core is composed on concentric rings of glass whose refractive indices decrease from the center axis. The purpose is to reduce modal dispersion and thereby increase fiber bandwidth.
Graphical User Interface (GUI) Computer interface that lets users access programs and enter data by using a mouse; considered to be user-friendly.
Ground A conducting connection, whether intentional or accidental, between an electrical circuit (telecommunications) or equipment and earth, or to some conducting body that serves in place of the earth.
Header duct (trenchduct, feeder duct) A raceway of rectangular cross-section placed within the floor to tie distribution duct(s) or cell(s) to the telecommunications room.
Headroom (also called Overhead or Margin) The number of decibels by which a system exceeds the minimum defined requirements. The benefit of headroom is that it reduces the bit error rate (BER), and provides a performance ‘safety net’ to help ensure that current and future high speed applications will run at peak accuracy, efficiency and throughput.
Hertz (Hz) A measure of frequency as defined in units of cycles per second.
High-Bit Rate Digital Subscriber Line (HDSL) A transmission technology that transmits over two twisted cable pairs up to a DS1-level signal, using any one of the following line codes: Binary / 1 Quaternary (2B1Q) Carrierless AM/PM, Discrete Multitone ("DMT"), or Binary / 1 Octel ("3BO").
HIGH DEFINITION TELEVISION (HDTV) An improved television system which provides approximately twice the vertical and horizontal resolution of existing television standards. It also provides audio quality approaching that of compact discs.
Home Run Telephone system wiring where the individual cables run from each telephone directly back to the central switching equipment. Home run cabling can be thought of as “star” cabling. Every cable radiates out from the central equipment. See also Star Wiring, Daisy Chain.
Horizontal Cabling The cabling between and including the telecommunications outlet and the horizontal cross-connect.
Horizontal Cross-Connect (HC) The HC is a location for the cross-connect of horizontal cabling to other cabling and equipment.
HTML (Hypertext Markup Language) the set of "markup" symbols or codes inserted in a file intended for display on a World Wide Web browser. The markup tells the Web browser how to display a Web page's words and images for the user.
HTTP (Hypertext Transfer Protocol) The Hypertext Transfer Protocol (HTTP) is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. HTTP is an application protocol relative to the TCP/IP suite of protocols, which are the basis for information exchange on the Internet.
Hub In data communications, a hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions. Hubs aren't switches as they have very little intelligence, if any, and don't set up transmission paths.
Hybrid cable An assembly of two or more cables, of the same or different types or categories, covered by one overall sheath.
Hybrid Connector A connector containing both optical fiber and electrical conductors.
Insertion loss (1) The loss resulting from the insertion of a device in a transmission line, expressed as the reciprocal of the ratio of the signal power delivered to that part of the line following the device to the signal power delivered to that same part before insertion.
Insertion loss (2) In an optical fiber system, the loss of optical power caused by inserting a component, such as a connector, coupler or splice, into a previously continuous optical path.
Insulation Displacement Connection (IDC) A wire connection device that penetrates the insulation of a copper wire when it is being inserted (punched-down) into a metal contact, allowing the electrical connection to be made.
Intelligent Hub Telecommunications cable(s) that are part of the campus subsystem that connect one building to another.
Interbuilding Backbone Telecommunications cable(s) that are part of the campus subsystem that connect one building to another.
Interconnection A connection scheme that provides direct access to the cabling infrastructure and the ability to make cabling system changes using equipment cords.
Intermediate Cross-Connect (IC) The connection point between a backbone cable that extends from the main cross-connect (first-level backbone) and the backbone cable from the horizontal cross-connect (second-level backbone).
Intermediate Distribution Frame (IDF) In a central office or customer premises, a frame that (a) cross connects the user cable media to individual user line circuits and (b) may serve as a distribution point for multipair cables from the main distribution frame (MDF) to individual cables connected to equipment in areas remote from these frames.
Intrabuilding Backbone Telecommunications cable(s) that are part of the building subsystem that connect one equipment room to another.
Jumper Wire An assembly of twisted-pairs without connectors on either end used to join telecommunications links at a cross-connect.
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