backboard - A panel (e.g., wood, metal) used for mounting connecting hardware and equipment.

backbone - 1. A facility (e.g., pathway, cable, conductors) between any of the following spaces: telecommunications rooms, telecommunications enclosures, common telecommunications rooms, floor-serving terminals, entrance facilities, equipment rooms, and common equipment rooms. (TIA) 2. In a data center, a facility (e.g., pathway, cable, conductors) between any of the following spaces: entrance rooms or spaces, main distribution areas, horizontal distribution areas, and telecommunications rooms.

backbone bonding conductor - A copper conductor extending from the telecommunications main grounding busbar to the farthest floor telecommunications grounding busbar. (TIA) See also telecommunications bonding backbone interconnecting bonding conductor (TBBIBC).

backbone cable - See backbone and backbone cabling.

backbone cabling - Cable and connecting hardware that provide interconnections between telecommunications rooms, equipment rooms, and entrance facilities. See also backbone.

backbone loop diversity - SA type of loop diversity that assigns circuits among different intrabuilding backbone cables.

backbone network An intermediate data network connecting two or more LANs. See also internetwork.

backbone pathway - The portion of the pathway system that permits the placing of main and high-volume cables between the entrance location and all cross-connect points within a building and between buildings.

backbone raceway - See backbone pathway.

back end equipment - The equipment component of a distributed antenna system that is located in an area of coverage and receives and transmits signals to the headend.

backfill - Earth placed outside foundation walls, or in cable trenches, for filling and grading back to a finished state.

backplane - See switch matrix.

backpressure - A flow control mechanism used to pause data transmission.

backscatter coefficient The ratio of backscattered light to transmitted light. The backscatter is a fixed percentage of the transmitted light.

backup - A copy of the data stored on a device.

backup path - A secondary or alternate channel for signal flow. It is typically used when there has been a failure of the main (primary) path.

backup storage - The ability to provide the means to recover from primary storage failure and the corresponding loss of data, a process typically referred to as disaster recovery. See also disaster recovery.

BACnet - See building automation and control network (BACnet®).

BACnet broadcast management device (BBMD) - A BBMD is one of the BACnet/IP broadcast management methods outlined in ISO 16484-5. This standard incorporates all amendments to ANSI/ASHRAE Standard 135 since 1995.

BACnet® interoperability building block (BIBB) - The purpose of a BIBB is to simplify interoperability into common functions that are intuitive to specifiers and owners and then define a name and set of simple BACnet requirements for each.

BACnet® Testing Laboratories (BTL) - The BACnet Manufacturer's Association offers a product testing and listing program for building automation products that have BACnet capability. Laboratories that conduct such testing and listing services are known as the BACnet Testing Laboratories.

BACnet® virtual link layer (BVLL) A BACnetllntemet protocol communication is implemented by defining a new protocol layer called the BACnet virtual link layer. The BVLL provides the interface between the BACnet Network layer and the underlying capabilities of a particular communications subsystem.

badge reader - See card reader.

badging software - Security software that is capable of creating a photo identification badge.

balanced cable Two or more insulated pairs of wires-identical in composition, size, and length-uniformly twisted together.

balanced copper cable - A cable consisting of one or more copper symmetrical cable elements (twisted-pairs or quads). See also balanced cable.

balanced line A transmission line that consists of a balanced cable pair whose transmit and receive voltages, at any point on the line, are equal in magnitude but opposite in phase with respect to ground.

balanced twisted-pair cable - See balanced cable.

balloon float - A helium filled balloon device used to assist in the verification of line of sight in point-to-point radio communications

balun - A balanced-to-unbalanced circuit coupling device, used to convert from unbalanced to balanced transmission, and provides impedance matching for connecting twisted-pair to coaxial cable.

bandwidth 1. A range of frequencies available for signaling expressed in hertz. 2. The information handling capability of a medium, expressed in units of frequency (hertz).

bar code card An access control card with identification information encoded in the bar code format.

barrel connector A female-to-female adaptor used to join two connectorized segments of coaxial cable together.

base Describes the number of signals traveling over media at the same time. Base is a shortened form of baseband, which has only one carrier channel and no multiplexing.

baseband An unmodulated, nonmultiplexed digital signal that by definition occupies the entire media bandwidth during each transmission. Baseband transmissions using multiplexing techniques are generally referred to as digital broadband. See also broadband.

baseboard pathway A distribution method in which channels containing cables run along or within the baseboards of a building or modular furniture.

basefining 1. The process of defining and documenting existing network characteristics. 2. A term used to describe the top view of surveyed terrain with elevations, benchmarks, natural features, and existing structures.

base station (BS) The fixed part of a mobile radio frequency network through which mobile and portable terminals (or stations) communicate. In the cellular industry, this may be called a base transceiver station.

basic link test configuration Obsolete term. Refer to permanent link.

basic rate interface (BRI) An integrated services digital network interface standard that consists of two B-channels and one 16 kb/s D-channel.

basic service set (BSS) - A single wireless LAN access point and its associated clients, loosely equivalent to a wireless collision domain.

battery backup A secondary energy source used to power devices in the event the primary energy source fails.

baud The measure of how often a signal can be changed from one electrical state to another in one second. Used to describe low-speed transmissions and is not common in modern baseband or broadband systems.

bay - 1. A regular repeated spatial architectural element defined by beams, columns, or ribs and their support. 2. Floor-standing racks, frames, or cabinets to house telecommunications or equipment.

Bayonet Neill-Concelman (BNC) See BNC connector.

beacon 1. A device used to mark tower for aircraft avoidance. 2. A frame transmitted by wireless LAN access points at regular intervals to let its presence be known to clients within its transmit range.

beacon frame A special token ring frame that is transmitted by a network device when it detects a ring failure. The device sending the frame is said to be beaconing.

beam clamp A device attached to a building structure to hold cable supports or equipment.

beam width On an antenna radiation pattern for a particular plane, the angle between the half-power (3 dB) points of the main lobe, when referenced to the peak effective radiated power of the main lobe. Beam width is usually expressed in degrees.

bearing plate A steel plate placed under one end of a beam, column, or truss at a support point for load distribution.

bearing wall A wall supporting a load other than its own weight. (TIA)

be A logarithmic ratio of analog signal strengths; named in honor of telephone pioneer Alexander Graham Bell. bend loss A form of increased attenuation caused by (a) having an optical fiber curved around a restrictive radius of curvature or (b) microbends caused by minute distortions in the fiber imposed by externally induced perturbations.

bend radius The radius of curvature that a media can bend without signal degradation.

berm The stabilized or paved area of the shoulder.

bias tee A type of connection used to inject dc power to combine the ac radio frequency signal on one end of a coaxial cable, and tap it off at the other end, thereby allowing remote powered devices to operate without a separate local power source.

biased door contacts A high-security door contact that uses a "biasing" magnet mounted inside the read switch part of the door contact package.

biconic A type of optical fiber connector developed by AT&T; exists in multimode and singlemode versions.

bid form bid form A prepared document that the bidder will submit to the tracking agent, owner, or contracting agent

bidders' conference A meeting conducted by the issuer of a request for quote or request for proposal to review and address any questions from respondents (bidders) with regard to the bid documents.

bidding documents All construction documents issued to bidders before the signing of an owner-contractor agreement.

bidirectional signaling Signals that pass in opposite directions between two transmitters. In a twisted-pair cable, this may be on the same or different pairs. Wireless and optical fiber systems also may operate in a bidirectional manner. Contrast with unidirectional signaling.

bill of material (BOM) A list of the quantity and specific types of materials to be utilized on a project. This list also should consider exempt materials (e.g., screws, bolts).

binary A numbering system using a base number of 2. Digital signals may be described as binary signals. When only two states or conditions are present, they are typically represented as on/off, open/ closed, ground/open, high/low, yes/no, or positive/negative. When printed out, they are typically expressed as one (1) and zero (0).

binary digit (bit) 1. The smallest unit of information in digital systems. 2. Zeros and ones used to represent data processed by digital devices.

binary digital system A system in which the data rate is determined by the baud rate and the number of bits encoded per baud interval.

binary phase shift keying (BPSK) A modulation scheme using phase-shift keying between two phase states, normally 180 degrees apart.

binder A tape or thread used for holding assembled cable components in place.

binder group One of two or more bound copper pairs or optical fiber strands within a cable.

biometrics An automated method of recognizing a person based on physiological or behavioral characteristics.

bipolar signal A signal that assumes both positive and negative voltage values. Many bipolar coding schemes attempt to minimize radiated emissions by alternating polarities (causing the signal to sum to zero over time).

bipolar violation Two pulses of the same polarity in a bipolar coding scheme that normally requires alternate signal pulse polarities. A bipolar violation may be an error condition or may indicate a special state in the coding scheme.

-bis A suffix applied to a protocol that identifies the second version of the protocol (e.g., V.32bis).

bit 1. The basic unit of digital information, used to indicate the existence of one of two binary states or conditions (e.g., current flow or no current flow, on or off). 2. A digital pulse representing a one (1) or a zero (0); contracted from the phrase "binary digit." 3. A binary digit; the smallest element of information in binary systems. It is either a logical one (1) or zero (0), also called "an on or an off bit" of binary data.

bit error rate (BER) 1. The ratio of incorrectly transmitted bits to total transmitted bits. A primary specification for all transmission systems, it is usually expressed as a power of 10. The number of errors made in a digital transmission as compared to complete accuracy. 2. The fraction of bits transmitted incorrectly. See also attenuation-to-crosstalk ratio and signalto-noise ratio.

bit per second (bls) A unit of measure used to express the binary data transfer rate of a device, system, or communications channel. Also called bit rate.

bit rate Transmission of a binary signal measured in bits per second.

bit stream A series of binary digits and ones} representing the message being transferred between devices.

bit time The inverse of the data transfer rate. See also data transfer rate.

bit-8 zero substitution (B8ZS) A bipolar coding scheme in which successive "1s" are sent as voltage pulses with alternating polarity. Additionally, a bipolar violation is intentionally sent for an eighth consecutive "0," in order to meet a minimum number of pulses required to maintain network synchronization. B8ZS line coding is most commonly found with T1 and integrated services digital network basic rate lines.

blank cell The hollow space of a cellular metal or cellular concrete floor unit without factory installed fittings. (TIA)

blended floor system A combination of cellular floor units with raceway capability and other floor units with raceway capability, systematically arranged in a modular pattern. (TIA)

block (connecting) See connecting hardware.

blueprint A reproduction of an architectural plan and/or technical drawing that provides details of a construction project or an existing structure.

Bluetooth© A low-power radio frequency personal area network technology that enables cordless data transfer between Bluetooth equipped devices at short range.

BNC connector A coaxial connector with twist-on bayonet locking coupling.

bolt position switch A miniature switch used on or in a locking device to monitor whether the locking bolt is in the locked (projected) or unlocked (retracted) position

bond 1. An electrical connection using a low-resistance path. 2. A written obligation under seal to guarantee that specific documents are accurate or that the bonded party will meet specific requirements, in a specific way, within a specific time period.

bonded pair Design that affixes two insulated conductors together.

bonding The permanent joining of metallic parts to form an electrically conductive path that will ensure electrical continuity and the capacity to conduct safely any current likely to be imposed. (TIA)

bonding conductor (BC) A conductor used specifically for the purpose of bonding.

bonding conductor for telecommunications (BCT) A conductor that interconnects the building's service equipment (power) ground to the telecommunications grounding system.

booster An amplifier inserted into a cable to increase the signal amplitude in order to compensate for signal loss due to attenuation.

boring A method to displace earth under the ground without breaking the ground surface (trenching) or cutting ground surfaces (e.g., sidewalks, driveways, parking lots, road surfaces). Normally, as dirt is displaced or removed, conduit is inserted.

borings Sample cylinders of subsurface material, taken at varying depths, to determine the character of the bearing material.

bottom-up design See physical design process.

bounded medium A term used to describe cabling or waveguide. Contrast with unbounded medium.

braid A group of non-insulated conductors interwoven to surround one or more insulated conductors. (TIA)

branch A cable run in a coverage area that connects one or more building automation system devices.

branch access A form of resource access where connection to a LAN is made from a LAN-connected station at another organizational site using a telecommunications link.

branch splice A splice in which one cable is spliced to multiple cables.

breakout An optical fiber cable that has an individual jacket for each tight-buffered fiber.

bridge A Layer 2 networking device used to connect separate LAN collision domains (or network segments) to extend network reach or selectively isolate network traffic.

bridged jack A dual-position modular female jack where all pins of one jack are permanently bridged to the other jack in the same order. (TIA)

bridged tap A connection that enables multiple appearances of the same cable pair at several distribution points. (TIA)

bridging A method to connect multiple devices or cables to a single appearance of a connection.

bridging (architectural) A system of bracing between floor beams to prevent lateral instability.

bridging clip An encased or bare metal clip utilized to couple cable conductors on a connecting block and provide a point of physical disconnection.

bridle ring A ring that is circular in shape but is open rather than closed. It has a pointed shaft at its apex that is threaded for installation into wood or prethreaded devices.

broadband 1. An analog design simultaneously using multiple communication channels separated by guard bands. 2. Sometimes used to describe a highspeed digital signal associated with backbone or multiplexed transmissions.

broadcast A technique for sending data simultaneously to all devices attached to a network with a single transmission. See also multicast and unicast.

broadcast domain The span of a LAN as represented by the devices capable of receiving a Network layer datagram addressed to all.

broadcast storm A series of retransmitted broadcasts caused by uncontrolled duplication of the original message.

browser Applications software used to access Web-based content.

browser mode A form of remote access where the remote station accesses LAN resources through a Web server on the LAN and obtains access to resources designed to operate in a Web browser environment. Contrast with control mode, terminal mode, and transparent mode.

bucket lift Personnel lift composed of a large bucket mounted on the end of an extendable arm in which the user stands.

buffer A temporary storage area in a networking device used to hold incoming data until it can be processed.

buffer coating A protective thermoplastic material that is applied to the acrylate layer of the optical fiber to protect against environmental hazards. May be more than one layer. See also coating.

buffer tube A supplemental loose-fitting cover, which is applied over the primary coated optical fibers at the time of installation.

buffering The process of providing a supplemental air supply to pressurized cables during splicing operations.

building automation and control network (BACnet®) An industry standard protocol for building automation and control networks developed under the auspices of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE), published as ANSI ASHRAE standard 135-2004. BACnet defines a four-layer architecture that includes the Physical, Data Link, Network, and Application layers of the Open Systems Interconnection Reference Model (ISO 7498).

building automation system (BAS) Equipment and telecommunications infrastructure that supports monitoring, control, operation, and management of building services. (TIA)

building automation system outlet A connecting device between a horizontal cable and a coverage area device. (TIA) building code Construction requirements that are adjudicated into law by the authority having jurisdiction.

building core A three-dimensional space, permeating one or more floors of the building and used for the extension and distribution of utility services (e.g., elevators, washrooms, stairwells, mechanical and electrical systems, telecommunications) throughout the building. (TIA)

building distributor (BD) A distributor in which the building backbone cable(s) terminate(s) and at which connections to the campus backbone cable(s) may be made. International equivalent term for intermediate cross-connect.

building entrance The point where services media enter or leave the building. See also entrance room or space (telecommunications) and entrance facility (EF [telecommunications]).

building entrance facility (BEF) See entrance facility (EF [telecommunications]).

building entrance protector A device or devices used to terminate cables entering or leaving buildings. It provides a housing for the voltage and currentlimiting modules to protect the cable pairs from lightning and foreign voltage and/or current.

building entrance terminal Cable termination equipment 'used to terminate outside plant cables at or near the point of building entry.

building grounding electrode system A network of grounded building components (e.g., metal underground water piping, metal building frame, concrete-encased electrode, a ground ring and rod, pipe electrodes) that is used or can be used for grounding/earthing purposes.

building module The standard selected as the dimensional coordination for the design of the building. The international standards have established a 100 mm (4 in) basic module. This produces modular coordination to all building materials, products, and utilization of the floor space.

building plan The representation of a building project.

building signaling system See building automation system.

building specification The detailed written description of a building project. Bull-Line TM See pull rope.

bullwheel A large wheel used to maintain an arc when feeding large cables into a backbone pathway.

bundle 1. Many individual optical fibers contained within a single jacket or buffer tube. Also, a group of buffered optical fibers distinguished in some fashion from another group in the same cable core. 2. Also used to indicate time and common handling of multiple cables routed together.

bundled cable An assembly of two or more cables continuously bound together to form a single unit. (TIA) Contrast with hybrid cable.

bundled fiber Group of buffered optical fibers distinguished in some fashion from other groups.

buried cable A cable installed under the surface of the ground in such a manner that it cannot be removed without disturbing the soil. (TIA) See also direct-buried cable and underground cable.

buried entrance An entrance facility in which cables enter or leave the building below grade rather than running in conduit.

burn-in Running devices prior to their use in service.

bursty A characteristic of digital transmission where the transmission rates have large variations during short periods of time.

bus topology (physical) 1. Networking topology, in which each communications device or network has a single connection to a shared medium that serves as the communications channel. Also called a point-to-multipoint topology. 2. A linear configuration where all network devices are connected using a single length of cable. It requires one backbone cable to which all network devices are connected.

butt configuration A configuration where one or more cables enter the splice case (end cap) from the same direction.

butt set See telephone test set.

butt splice A splice in which one or more conductors enter the module or connector from the same direction.

butterfly detail A maintenance hole diagram showing all four walls and detailing route and splicing locations of cable passing through the maintenance hole.

byte A data unit made up of eight bits. Also called an octet.