B

B 911 - This is also known as Basic 911 emergency service. It is the older version of the 911 system and it is what public service commissions want phone companies to phase out. B 911 does not provide automatic location information. In many cases (depending on the CO switch/911 software serving the customer that makes the 911 call), it does not provide automatic number identification.

B Channel - The "bearer" channel of an ISDN circuit. It carries 64Kbp/s of end-user data. The other ISDN channel is referred to as the D or data channel, which is 16Kbp/s and carries phone company signaling along with the other stuff that makes the ISDN circuit work. The two categories of ISDN are the BRI (Basic Rate Interface 2B channels and 1D channel) and the PRI (Primary Rate Interface 23B channels and 1D channel). For a relational diagram of the two types of ISDN lines, see Integrated Services Digital Network.

B Connector - A wire-splicing connector for splicing twisted pair wire, also called beans. Beans are shaped like a plastic tube that is about as big around as a drinking straw, but only an inch long. They have metal teeth inside them so that when two wires are crimped inside, they make a good connection and don't slide out. Beans can also have a water-retardant jelly inside them as well.

B-ICI (Broadband InterCarrier Interface) - This ATM backbone solution uses ATM to multiplex multiple services, such as cell relay, voice DS1, frame relay (PVC) over one ATM link (i.e., DS3 44.736 Mbps, STS- 3c 155.52 Mbps, STS-and 12c 622.08 Mbps).

B Washer, Curved - The washer used between a telephone pole and a strand clamp when installing pole attachments .

B3ZS (Bipolar 3-Zero Substitution) - A line-coding/data-transmission format. Transmission formats are used to prevent too many consecutive zeros from being transmitted. If too many zeros go down the line in a row, the transmission line effectively becomes a flat line, with no timing.

B8ZS (Binary 8-zero substitution) - A line-coding/data-transmission format. Transmission formats are used to prevent too many consecutive zeros from being transmitted. If too many zeros go down the line in a row, the transmission line effectively becomes a flat line, with no timing. If a sequence of eight bits are detected prior to being transmitted, they are replaced with a different pre-determined byte that is not all zeros.

Back Bone - The part of a communications network that connects main nodes, central offices, or LANs. The backbone usually has its own high-speed protocol, such as switched token ring or FDDI for LAN interconnections, and SONET for central-office and main-node interconnections.

Back-Feed Pull - When it is difficult to get large cable pulling equipment into end locations of a cable installation, outside plant construction personnel use a technique called a back-feed pull. If there is a vault or hand hole that the cable passes through between the end points, the cable will be fed in two parts. The first section of cable will be fed one direction from the mid-point. After the first half is fed, the remaining cable is unreeled and fed through the opposite direction to other end point .

Back Haul - A long-distance service term. Sometimes you can save money by creatively routing long-distance calls. Back haul is a routing term that means routing a call past its destination and then back. Many new long-distance companies are providing less-expensive longdistance services to specific cities and conglomerate long-distance companies take advantage of this by back hauling phone calls. Airline passengers are often back hauled because it is less expensive to have a lay-over in another nearby larger city—even though it is beyond your destination.

Back Hoe Fade (slang) - The cutting of a buried fiber optic that connects two communications nodes. It is called a fade because in some equipment architectures, not all communications are cut off—they are either divided or rerouted. To some, this is a "fade" in communications service, not a complete outage.

Back Plane - The main electronic PC board in a communications equipment cabinet that has slots or connectors for circuit cards to be plugged into. The back plane in almost all key service units and PBX card cages is where the power bus, CPU bus, and the control bus are located .

Backward Channel - The channel that flows upstream in an asymmetrical transmission. An asymmetrical communications transmission that is characterized by one direction being very fast compared to the other. Cable TV is an example of asymmetrical communication. The cable TV head end sends massive amounts of video and audio information down a coax one way and the cable TV set-top decoder boxes send small amounts of ID and status information the other way back to the head end over the same coaxial connection. Sometimes asymmetrical channels are referred to as "upstream" for the slow channel and "downstream" for the fast channel, or "forward" for the fast channel and "backward" for the slow channel.

Backward Explicit Congestion Notification (BECN) - A bit in the overhead of a data packet travelling in a frame-relay network. This bit is set to 1 if the packet travels through an area of network congestion that is opposite (or backward) of its flow. This bit is a signal from the frame- relay network to higher-level protocols within DTE and DCE to take flow-control action, as appropriate. An example of flow-control action would be to not attempt to exceed the Committed Information Rate (CIR) for the connection. This would prevent the unnecessary transmission of low-priority frames that would surely be discarded.

Baffle - An enclosure for the back of a loudspeaker that improves its sound quality by improving its acoustic profile. Baffles are made of thin, flexible rubber foam and are frequently used on ceiling intercom speakers and automobile speakers. They usually cost about $6.00 to $10.00 each, depending on the size of the speaker.

Balance, Circuit - An electronic circuit that can be active (using external power) or passive (using only capacitors, resistors, and inductors) that is attached to a twisted copper pair to even out the electronic characteristics of both wires. Balance is very important in a transmission line. If the two wires or pair is not balanced, noise is created on the line, which interferes with the transmission signal.

Balun (Balanced/Unbalanced) - A device used for matching impedances or transmission characteristics between different media so that electronic signals can pass from one to the other without being severely attenuated. Baluns that match twisted pair and coaxial cable are very common in local-area network environments.

Band, Citizens - A low-power two-way transmission radio band in the United States. There are actually two types or bands of CB radio. They are 26.965 MHz to 27.225 MHz and 462.55 MHz and 469.95 MHz

Band-Elimination Filter - A band-elimination filter is a circuit used to pass a certain range of frequencies away from specific equipment or devices to ground, or somewhere they are wanted. Radio-frequency interference is easily eliminated with the correct band-elimination filter. Band-elimination filters are also called RFI (Radio Frequency Interference) filters, RFI suppressors and EMI (Electromagnetic Interference) suppressors. They work by providing an easier path for noise to go through, rather than your electronic device (such as your telephone or modem). Many RFI filters are on the market, and some are adjustable to different frequencies. Some are modular instead of hard wired into the NI or jack so that you can plug them right into your phone line. These filters are not XDSL compatible because XDSL has its own built-in line conditioning. Further, filters are not recommended for any digital service line.

Band, Frequency - The following are the defined boundaries of radio frequency bands:

ELF Extremely Low Frequency below 300 Hz

ILF Infra Low Frequency 300 to 3000 Hz

VLF Very Low frequency 3 kHz to 30 kHz

LF Low Frequency 30 kHz to 300 kHz

MF Medium Frequency 300 kHz to 3000 kHz

HF High Frequency 3 MHz to 30 MHz

VHF Very High Frequency 30 MHz to 300 MHz

UHF Ultra High Frequency 300 MHz to 3000 MHz

SHF Super High Frequency 3 GHz to 30 GHz

EHF Extremely High Frequency 30 GHz to 300 GHz

THF Tremendously High Frequency 300 GHz to 3000 GHz

Band, Marking - A label placed around an insulated wire or fiber optic for identification. Some are printed on during manufacture and some are attached during installation.

Band-Pass Filter - A band-pass filter is used in frequency-division multiplexing, as well as the equalizer in your stereo. It is usually a capacitor/ resistor/inductor network that has a resonant frequency and a rating of how well it passes a band of frequencies and blocks out others, called the Q (quality) of the circuit. The resonant frequency of the circuit is the frequency that the circuit will pass. Band-pass filters are used in ADSL applications. See DSL Inline Filter.

Bandwidth - The difference in frequency between the top end of a channel and the bottom end. A good example of a bandwidth is sound. If you are listening to a sound, such as music, you notice the different pitches. All of these pitches or tones of sound are audio information that your ear can process. The sounds are actually vibrations. Bass tones vibrate at a slow rate, about 20 to 700 vibrations per second. Treble tones vibrate faster, from 3000 vibrations per second to 17,000 vibrations per second. The total bandwidth (vibration range) that you are listening to is about 17,000 — 20 = 16,980 vibrations per second. This is the range or bandwidth of human hearing.

Bandwidth Allocation - The process of dynamically assigning communications resources to users and software programs within a network. The process incorporates predetermined priority levels for data based on its time sensitivity. Generally, when a network becomes congested, lower-priority traffic is dropped. The dropped traffic is retransmitted at a later time. For an example of a priority level parameter, see ABR and MCR.

Bandwidth Control - The process of allowing customer traffic to run through a frame-relay network at a rate faster than the CIR (Committed Information Rate) setting for the particular DLC (Data Link Channel) when traffic is low. This is also referred to as throttling or rate adaptation.

Bandwidth-Control Elements (BCE) - The parameters of a frame-relay Data Link Connection (DLC) that determine the amount of data that will be accepted into the network over a period of time, and what delivery priority they have. Bandwidth-control elements are:

CIR Committed Information Rate

AIR Allowed Information Rate

EIR Excess Information Rate

Be Excess Burst

Bc Committed Burst

Tc Time in seconds

Their relationships are as follows: CIR = Bc/TcAIR + CIR + EIR

Bandwidth Reservation - Another term synonymous with bandwidth allocation. See Bandwidth Allocation.

Banjo - This is also called a beaver tail or break-out block. It is used by technicians to connect other devices to modular jack wiring for testing purposes. Banjo is a trademark of Harris Dracon Division.

Bantam Connector/Plug - A standard plug and jack that is used to interface test equipment with digital circuits (DS1, DS3, STS-1) that are wired to DSX patch panels .

Barge In - When an attendant or operator adds themselves on to a line that is already in use. See also Busy Override.

Barrel Connector - A gender-changing device that connects two male coaxial F connectors together.

Base Station - A device that connects wireless communications to the land-line phone network. Base stations can be integrated into a BTS. See also Cellular.

Baseband - The opposite of broadband. Baseband is the transmission of one signal over a media or carrier. Telephone conversations in themselves are baseband. Applying 24 telephone conversations to a T1 carrier is a broadband application. Because T1 has more than one channel within one transmission, it is broadband. See also Broadband.

Baseband Modem - A modem that modulates and demodulates a single digital data transmission to and from another modem. Baseband modems can be used over plain twisted-pair wire with no telephone service. In this application, they are better known as short-haul modems, which extend peripheral devices (such as printers) 50 to 1000 feet from their host.

BASIC (Beginners All-Purpose Symbolic Instruction Code) - A type of programming language that has many variations, depending on the developer. Microsoft Visual Basic is a newer version of this style of programming.

Basic Rate Interface - The small size ISDN line (the other size is a primary rate interface). It consists of two bearer or "B" channels and one data or "D" channel. The B channels are 64Kbp/s each. With the appropriate service package from the phone company and correct terminal adapter, you can talk on one B channel while using your computer modem on the other B channel. When your phone conversation ends and you hang up, the terminal adapter will send a message back to the phone company through the D channel that connects both B channels together for a total transmission bandwidth of 128Kbp/s for your computer automatically.

Battery - A device that converts chemical energy to electrical energy. Batteries of over 1.5 V (nominally) are composed of cells, each cell being a smaller battery that is equal to 1.5 V in electrical potential. A 12-V lead- acid automotive-type battery is comprised of eight 1.5-V cells in series that add up to 12 V. Some batteries are re-chargeable, depending on the two chemically interacting materials that the battery is made of.

Battery Back Up - There are two different types of battery back-up systems. There are rectified power sources, which continuously charge batteries that power a system. This system is used by telephone companies for their central offices. When the power goes out, the charging on the batteries stops, but the system still runs because it's running on the batteries. The other type of battery back up is a UPS (uninterruptable power supply), which is always on standby. When the power goes out, the UPS converts the DC battery power to AC power to run the system. Which system you use depends on the type of power that your phone system requires. If you have the option of running on DC, the rectified battery back-up is far superior in reliability, and they are available in many different sizes. Reltec is a well-known manufacturer of these systems.

Baud Rate - The actual bit rate on a communications line. Not to be confused with bit rate, which includes data compression.

Baum - An impedance-matching transformer used in RF applications. Fifty to 75 ohms is typical.

Bay - A place in a computer cabinet where a peripheral device, such as a disk drive, can be installed.

BBN (Bolt, Baranek and Newman, Inc.) - The company that developed and maintained the ARPANET (Later the Internet) core gateway system.

BBS (Bulletin Board System) - A Website that can be accessed by users that acts as a central source of information. BBS Websites are usually set up by particular interest category.

Bc (Committed Burst) - An amount of data that is permitted onto and over a frame-relay network DLC (Data Link Connection) over a specific amount of time. See also Bandwidth-Control Element.

BCD (Binary Coded Decimal) - A four-bit code that represents the numbers zero through nine in binary. It is basically implemented as a short cut for entering many binary numbers into a machine-language program. Logic circuitry decodes the BCD to binary for the microprocessor.

BCM (Bit-Compression Multiplexer) - A multiplexer that increases bandwidth by encoding data bits into a special format.

BDFB (Breaker Distribution Fuse Bay) - The point in a central-office power system where each DC feed to all rows of equipment are equipped with a fuse or a breaker. The BDFB is a central location for power distribution. Generally, each rack of electronic equipment is also equipped with its own FAP (Fuse Alarm Panel).

Be (Excess Burst) - One of the frame-relay bandwidth-control elements. It is sometimes a negotiated service between customers and service providers. An excess burst is an amount of data in bytes (not a bandwidth, like Bc is). Excess burst data over a frame-relay network is marked Discard Eligible (De) by the network. If the network is not congested, there is a very good probability that the data marked De will be delivered. If the frame relay network is congested, it will discard data marked De. It is the amount of data that exceeds the Committed Burst (Bc) setting of a frame-relay DLC (Data Link Connection). See also Bandwidth-Control Elements.

Beacon - A frame from a token-ring or FDDI device that indicates a serious problem within the ring's network, such as a broken fiber optic. The beacon frame contains the address of the station assumed to be down.

Bean - A wire-splicing connector for splicing twisted-pair wire. Beans look like a plastic tube that is about as big around as a drinking straw, but only an inch long. They have metal teeth inside them so that when two wires are crimped inside, they make a good connection and don't slide out. Beans can also have a water-retardant jelly inside them as well. For a photo, see Plain B Wire Connectors.

Beaver Tail - Another name for a Harris Dracon Division Banjo or a similar break-out device. The Banjo is a device for connecting test equipment to the wiring in modular jacks. For a photo, see Banjo.

BECN (Backward Explicit Congestion Notification) - A bit in the overhead of a data packet travelling in a frame-relay network. This bit is set to 1 if the packet travels through an area of network congestion that is opposite (or backward) of its flow. This bit is a signal from the frame- relay network to higher-level protocols within DTE and DCE to take flow-control action, as appropriate. An example of flow-control action would be to not attempt to exceed the Committed Information Rate (CIR) for the connection. This would prevent the unnecessary transmission of low-priority frames that would surely be discarded.

Bed-of-Nails Clip - A test clip similar to an alligator clip, except that it has a section of very sharp needle-like objects bunched together that poke through a wire's insulation when the clip is applied. These clips achieve a good connection for testing without stripping the insulation off the wire .

BEL This is an ASCII control-code abbreviation for bell. The Binary code is 0111000 Hex is 70.

Bell Operating Company (BOC) or Regional Holding Company At the time of the 1984 divestiture, there were 22 BOCs, grouped into seven Regional Bell Operating Companies (RBOCs) in the United States.

"BOCs:

Bell Telephone Company of Nevada

Illinois Bell Telephone Company

Indiana Bell Telephone Company

Michigan Bell Telephone Company

New England Telephone and Telegraph Company

US West Communications Company

South Central Bell Telephone Company

Southern Bell Telephone and Telegraph Company

Cincinnati Bell Company

Mountain Bell Telephone Company

Mountain States Telephone and Telegraph Company

Southwestern Bell Telephone Company

The Chesapeake and Potomac Telephone Company of Maryland

The Bell Telephone Company of Pennsylvania

The Chesapeake and Potomac Telephone Company of Virginia

The Chesapeake and Potomac Telephone Company of West Virginia

The Diamond State Telephone Company

The Ohio Bell Telephone Company

The Pacific Telephone and Telegraph Company

New Jersey Bell Telephone Company

Wisconsin Telephone Company

"RBOCs:

Ameritech Bell Atlantic Bell South NYNEX Pacific Telesis Southwestern Bell US West

Bell System Practices (BSPs) - A volume of standards that explain how to do everything from terminate an RJ11 jack to install a central office. They even had a standard on how to collect a past-due phone bill. The BSPs were a pre-1984 (divestiture) tool for operating phone companies. They are no longer widely embraced by the RBOCS or AT&T. New equipment manufacturers have their own instructions for operating and installing their products, and each RBOC has its own way of operating a communications company.

Bend Loss - The loss of transmission in a fiber-optic or twisted-pair cable because of a bend. Bending fiber-optic cable causes the light traversing through it to reflect outward, instead of down the core of the fiber. A bend in a twisted-pair wire causes the dielectric or insulation to change its electrical properties, which results in a loss of signal.

Bending Radius - The smallest or tightest bend that a Cat5, Cat7 or fiber can withstand under a tensile-pulling force without damaging its transmission characteristics.

BER (Bit Error Rate) - A way to measure data-transmission integrity. The bit error rate is a ratio of bad bits to good bits.

BERT (Bit Error Rate Test) - A way to measure data transmission integrity. The test gives a result as a ratio of bad bits to good bits.

Beta - A way of referring to a test site or test product. If a new revision is released by a manufacturer, the first sites that it is installed at is referred to a beta site.

BGP (Border Gateway Protocol) - An interdomain routing protocol that has been used in Internet core router applications to exchange reachability information with other "same system type" routers.

BGP4 (Border Gateway Protocol version 4) - The predominant inter- domain routing protocol used on the Internet. It is capable of aggregating routes listed within a router's memory, which reduces the size of routing tables.

BICSI (Building Industry Consulting Service International) - The provider of the RCDD (Registered Communications Distribution Designer) certification. The RCDD certification is often referred to as a BICSI (pronounced "bik-see") certification. The RCDD certification is designed to educate professionals in the area of physical network distribution, including twisted pair and optical media. More information can be found regarding BICSI certifications at http://www.bicsi.org.

Bidirectional Bus - A bus that connects devices that clock bits in as well as out of their shift registers. The devices that a bus is connected to make it unidirectional or bidirectional, not the bus itself. All buses are merely a group of parallel conductors that connect the shift registers of components, as well as the power for the devices.

Big Endian - A method of storing or transmitting data in which the most- significant bit or byte is presented first. The opposite is referred to as little-endian, which presents the least-significant bit first.

Billed Telephone Number - The number that is the regarded as the billing account number on a phone bill. Sometimes when a customer calls a phone company for service, the customer-service representative will ask the customer for the billed telephone number because that is the number that all the other customer's phone numbers and charges are referenced to. This method is used so that a customer doesn't get a phone bill for every individual phone line they have.

Binary - A number system that counts with only two digits, 0 and 1. We are all more familiar with the arabic base ten, which counts with ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. The following is a list of numbers and their binary equivalent. For a larger table of binary numbers, see Appendix E.

Binary Coded Decimal (BCD) - A four-bit code for representing the numbers zero through nine in binary. It is basically implemented as a short cut for entering many binary numbers into a machine-language program. Logic circuitry decodes the BCD to binary for the microprocessor.

Binary-to-Decimal Conversion - For a conversion table of Binary to Decimal and Hexadecimal, see Appendix E.

Binary-to-Hexadecimal Conversion - For a conversion table for binary to decimal and hexadecimal, see Appendix E.

Binder - A method of separating groups of 25 pairs in a twisted-pair cable with counts of more than 25 . Colored plastic ribbon binds, designates and separates each group of 25 pairs. The first binder group is white/blue pairs 1 to 25, the second is white/orange pairs 26 to 50, the third is white/green pairs 51 to 75, the fourth is white/brown pairs 76 to 100, etc. If you would like to see the entire list of binder groups and their associated pairs, see Color Code, Twisted Pair.

Binder Group - A method of separating groups of 25 pairs in a twistedpair cable with counts of more than 25. See Binder.

Binding Post - A reference used to identify where twisted copper pairs are terminated in access points, cross boxes, and terminals. Physically a binding post is a pair of teeth on a 66M150 block or a pair of %" lugs. Each binding post has a number. When a technician looks for a specific pair in a cable (called a cable pair), they refer to documents that list the pairs and which binding posts they are spliced to.

BIOS - Basic Input Output System residing in a PC. It contains the shift registers (dynamic RAM) used as buffers for sending bits to the specific hardware that they are intended for.

Biphase Coding - A bipolar (positive negative alternating) coding scheme originally developed for use in Ethernet. The clocking/timing signal is embedded into the data stream as the positive and negative switching cycle itself. This encoding scheme eliminated the need for separate clocking leads.

Bipolar - 1 A copper twisted-pair transmission method (or line format), where bits that are transmitted are alternated positive and negative. This transmission technique increases the distance a transmission can travel on a twisted pair. 2. A transistor.

Bis - French for encore.

BISDN (Broadband Integrated Services Digital Network) - A conceptual telecommunications service. When the idea of BISDN was conceived, it would have the ability to provide "on-demand" bandwidth to customers for various services, such as video, data transfer, etc. BISDN types of services have evolved through ATM and the Internet. Newer data-compression techniques and high-speed local telephone lines have made bandwidth on demand available through services other than ISDN. Frame-relay and ATM services provide excess information rates across networks and are available to customers at a relatively low cost. The standardization and wide spread use of Internet protocols, ATM feature flexibility, and the implementation of xDSL in local networks are the en- ablers of BISDN.

Bisync - A nickname for a tradition-breaking data-communications protocol developed by IBM. It was one of the first and perhaps "the original" of the non character-code oriented protocols. Hence, the name came from bit-synchronous. The advantage of a noncharacter-oriented or bit synchronous protocol is that they are flexible in the types and sizes of data characters they can send (e.g., 7-bit or 8-bit, ASCII or EBCDIC). The official name for Bisync is SDLC (Synchronous Data Link Control) and eventually evolved to HDLC (High-Level Data-Link Control). HDLC was the basis for the LAP (Link-Access Procedure) developed by the ITU (then the CCITT), which ultimately became the basis for the X.25 standard in 1976.

Bit (Binary Digit) - A unit of data that is represented as a one or a zero. Inside most data devices, a bit is physically a positive 5 volts or 0 volts.

Bit Error Rate (BER) - A way to measure data transmission integrity. The bit error rate is a ratio of bad bits to good bits.

Bit Interleaving - A simple way to time-division multiplex by interleaving individual bits, instead of bytes or packets. Timing of the two ends is not as complex with this method. Used in X.25 and HDLC, not in T1 or T3.

Bit Oriented - Communications protocols that use bits to represent control information in contrast to bytes. A byte can mean different things in the different varieties of character sets that are transmitted. Bit-oriented protocols are not character code sensitive.

Bit Parity - A way to check that transmitted data is not corrupted or distorted during the transmission. The way parity works is as follows. Take a bit stream that will be transmitted, add all the bits as binary numbers mathematically, and the resulting number is odd or even. Add a 1 at the end of the stream if the number is even and a 0 if the number is odd. When the bits are received at the other end, they are added up and compared to the last bit. If they add up to be an even number, then the last bit should be a 1. If they add up to an odd number, then the last bit should be a 0. If the case for either does not hold true, then the receiving end sends a request to retransmit the stream of bits. They are retransmitted, with the parity bit attached all over again. For example, a computer sends a bit stream of 10101011. Simply adding the bits gives a sum of 1 + 0 + 1 + 0 + 1 + 0 + 1 + 1 = 5. This is an odd number, so add a 0 to the end of the stream to make it 101010110. The bits are received at the other end, added together, and compared to the parity bit the same way. There are new and more sophisticated ways of checking for errors in data transmission, such as cyclic redundancy checking.

Bit Rate - The average net number of bits being transmitted over a communications line in a second, including compression and encoding techniques, as well as retransmission of corrupted data.

Bit Robbing - Bit robbing is often known as in-band signaling. The practice of taking a bit here and there in the beginning and end of a digital transmission for use in the overhead of the transmission equipment. Bit robbing is bad when the signals being multiplexed into the transmission are data. Robbing a bit from a data stream severely corrupts data. Bit robbing is a technique reserved for multiplexing multiple voice circuits onto a T1. Circuits intended to transmit data use out of band signaling or clear-channel signaling.

Bit Stream - A series of voltage pulses that represent a binary code. A serial data transport. A bit stream can exist on a transmission line or within the electronics of a data device.

Bit Stuffing - The temporary modification of user data during transmission so that it does not interfere with lower-layer signaling functions. For instance, in X.25, a flag byte is put before and after the frame. This byte is a 01111110. If the data being sent contains a 01111110, such as a lower case "w" (0111111), followed by a lower case "s" or lower case "a" (which both start with a 0), the data would be mistaken for a flag. This would cause random characters and bits to be lost, which would ultimately make transmission impossible beyond the error-correction stage. To fix the scenario, a "0" is inserted (or "stuffed") any time that five consecutive ones appear. The data is framed, transmitted, deframed, and then after every five ones, a zero is deleted (or "unstuffed"). The data is then handed to the packet layer.

Bits Clock - A device that provides a timing pulse in the form of a 1-0-1-01-0-1-0 bit stream. Bits clocks are used extensively in SONET networks. A bits clock provides the timing pulse that nodes in a network synchronize .

Bits Per Second - The average net number of bits being transmitted over a communications line in a second, including compression and encoding techniques, as well as retransmission of corrupted data.

Black Box - Usually a device that converts or routes one type of data or signal applied to the input to a desired useful output for a specific application. One company called "Black Box Corporation" specializes in the manufacture of these specialized devices.

Black Hole - A name for an area (or router) of an Internetwork where packets enter, but do not emerge. Thus, data is lost. Black holes can be caused by any of the following: system (router table) configuration, bad hardware, or an adverse operating environment (noncompatible equipment).

Blended Agent - An agent in a call center that receives calls from outside customers. When the incoming call rate slows down, it makes outgoing calls.

Blended Call Center A call center that receives calls from customers and also calls customers. Sometimes agents are dedicated to either inbound or outbound calls.

BLF (Busy Lamp Field) - A part of or an add-on module to a phone or console that allows the user to see multiple extensions and if that extension is in use (or busy).

Blocked Call - A call that cannot be completed because the Central Office or PBX switching capacity is full at the time the call was attempted. Blocking can occur at any point in a network where a call is switched (from CO to CO or from local to long distance). The caller with a blocked call either hears a fast busy or an intercept message that says "I'm sorry, all circuits are busy now. Please try your call again later."

Blocking - When a central office or PBX has fully utilized its capacity to connect calls, it blocks them. Callers trying to call in or out of a switch that is blocking calls will get a fast busy signal.

BNC (British Naval Connector) - A type of connector used on all different types of coax. It is keyed so that it locks into place and it has better transmission characteristics than an "F" connector .

BOC (Bell Operating Company or Regional Holding Company) - At the time of divestiture, there were 22 BOCs, grouped into seven Regional Bell Operating Companies (RBOCs). For a listing of the BOCs and RBOCs, see Bell Operating Company.

Body Belt - Used by communications/power/construction personnel to harness themselves to telephone/power poles or tower structures. This is also called a safety belt or a climbing belt. For a photo, see safety belt.

Bolt, Baranek and Newman, Inc. (BBN) - The company that developed and maintained the ARPANET (later, called the Internet) core gateway system.

Bond - 1. What telephone company construction personnel call the connection between the sheath of a telephone cable and an electrical ground. 2. An electrical connection.

Bonding - In ISDN the joining of two 64Kbp/s B channels together for one 128 Kbp/s channel.

Boot - To restart a computer or CPU-based system by physically turning it off, then back on, which resets the CPU. This is also called bootstrap.

Boot PROM (Boot-Programmable Read-Only Memory) - A memory chip with permanent programmed instructions burned into it. It is used to provide executable instructions to a computer device when it is initially turned on or restarted.

BootP - A protocol or subroutine used by a network node to determine the IP address of its Ethernet interfaces. This is necessary to restart or maintain a network transmission.

Border Gateway Protocol (BGP) - An interdomain routing protocol that has been used in Internet core router applications to exchange reachability information with other "same system type" routers.

Bounce - A common term used by technicians in place of reset, with regard to digital communication channels, such as T1s.

BPAD (Bisynchronous Packet Assembler Dissasembler) - A hardware- based device that inserts bytes into packet frames and vise-versa in packet multiplexing/transmission equipment.

BPS (Bits Per Second) - The average net number of bits being transmitted over a communications line in a second including compression and encoding techniques, as well as retransmission of corrupted data.

BPSK (Binary Phase-Shift Keying) - A method of transmitting binary bits in a form of frequency shift, or FM that is the same concept as frequency-shift keying. The difference is that with BPSK, you change the phase of the frequency, instead of the frequency itself. The two are shown in the diagram. If you look closely, you can see the changes in the waveforms that represent the switch from a one to a zero value.

Breakdown Voltage - The voltage at which insulation in a cable or an electronic device fails.

Break-Out Box - A test device that plugs into a data cable (i.e., RS232) and provides easy test access for each wire in the cable.

Breaker Distribution Fuse Bay (BDFB) - The point in a central-office power system, where each DC feed to all rows of equipment are equipped with a fuse or a breaker. The BDFB is a central location for power distribution. Generally, each rack of electronic equipment is also equipped with its own FAP (Fuse Alarm Panel).

BRI (Basic Rate Interface) - The small-size ISDN (Integrated Services Digital Network) line (the other size is a Primary Rate Interface). It is made up of two bearer or "B" channels and one data or "D" channel. The B channels are 64 Kbp/s each. With the appropriate service package from the phone company and correct terminal adapter, you can talk on one B channel while using your computer modem on the other B channel. When your phone conversation ends and you hang up, the terminal adapter will send a message back to the phone company through the D channel that connects both B channels together for a total transmission bandwidth of 128 Kbp/s for your computer automatically. For a diagram, see ISDN.

Bridge - A bridge is a device that connects two networks at the data-link level. The data-link level is the simplest protocol layer in the OSI to make a connection between two networks because no data interpretation is needed at this level. As a result, data can be transmitted with virtually no delay. In other words, a bridge simply decides whether the datagram/ packet should pass or not pass. They operate over segments that use the same protocol, such as Ethernet or token ring. Bridges can be used to extend a network over similar or dissimilar media, such as twisted pair to fiber optic. See also Source Routing Bridge and Transparent Bridge.

Bridge Clip - A metal clip (sometimes plastic insulated) used to electronically connect or bridge across the left side of a 66M150 block with the right side .

Bridge/Source Routing - A type of network bridge that relies on routing information provided by an external sending system.

Bridge Tap - A Y splice in a copper twisted-pair communications cable. It gets its name because the first splice is a straight through splice, and the second splice connects the wires by cutting or "tapping" them into the first splice. A bridge tap adds flexibility to telephone plant. A telephone company never knows which customer is going to use lots of pairs for their service and who will use only a few. To remedy the situation without installing 100 pairs of copper to each individual building, the telephone company installs the same 100 pairs into three or four buildings. This is done by bridge tapping the cable splices. The bad thing about bridge tapping is that it lengthens the pair. Length is bad for digital services (additional loss, and reactance), such as T1 and ISDN, so the bridge taps must be disconnected before these services are installed. On a cable drawing, bridge taps are shown as arrows and telephone cable is shown as a line .

Bridge/Transparent - A type of network bridge that learns which systems are on each network by listening to traffic and building its own reference tables.

Broadband - Incorporating more than one channel into a communications transmission. T1 is a broadband communications protocol because it carries 24 conversations over four wires. Cable TV is also broadband because it carries many TV channels over one coax.

Broadband Integrated Services Digital Network (BISDN) - A conceptual telecommunications service. When the idea of BISDN was conceived, it would have the ability to provide "on-demand" bandwidth to customers for various services, such as video, data transfer, etc. BISDN types of services have evolved through ATM and the Internet. Newer data- compression techniques and high-speed local telephone lines have made bandwidth on demand available through services other than ISDN. Frame relay and ATM services provide excess information rates across networks and are available to customers at a relatively low cost. The standardization and wide spread use of Internet protocols, ATM feature flexibility, and the implementation of xDSL in local networks are the enablers of BISDN.

Broadband Inter-Carrier Interface (B-ICI) - A reference to an ATM backbone solution. It uses ATM to multiplex multiple services, such as cell relay, voice DS1, frame relay (PVC) over one ATM link (i.e., DS3 44.736 Mbps, STS-3c 155.52 Mbps, and STS-12c 622.08 Mbps).

Broadcast - To send information in any form to more than one place.

Broadcast Address - A special address reserved for sending a message to all stations. A broadcast address is a destination address of all ones (in decimal, 255.255.255.255). See also IP Broadcast and Multicast.

Brouter - A device in a LAN, MAN, or WAN that performs the functions of a bridge and a router at the same time. A bridge converts a signal from one transmission media to another or one protocol to another. An example would be a device that converts an electrical signal to an optical signal so that a data transmission can be taken from an Ethernet LAN to a distant PC. A router is a device that routes data intended to be sent to certain devices to those devices. A common application for a router is to send Internet traffic only to the Internet and keep local traffic local. This increases the efficiency of the Internet connection because it is only receiving and transmitting traffic intended for it instead of all the traffic on the network. The following drawing depicts where routers, brouters, bridges, and a hub would be implemented in a small Ethernet LAN to MAN network.

Browser - A computer program that allows users to download World Wide Web pages for viewing on their computers. Two popular browser programs are Netscape Navigator and Microsoft Internet Explorer. The first browser program was called Mosaic, which was a text browser, as opposed to the newer graphical browsers.

BS - An ASCII control code abbreviation for backspace. The binary code is 1000000 and the hex is 80.

BSP (Bell System Practice) - A volume of standards that explain how to do everything from terminate an RJ11 jack to install a central office. They even had a standard on how to collect a past-due phone bill. The BSPs were a pre-1984 (divestiture) tool for operating phone companies. They are no longer widely embraced by the RBOCS or AT&T. New equipment manufacturers have their own instructions for operating and installing their products, and each RBOC has its own way of operating a communications company.

BSS (Base Station System) - A wireless communications device that manages radio traffic and bandwidth between a group of base transceiver stations.

BTA (Basic Trading Area) - Geographical boundaries defined within a cellular radio license.

BTN (Billed Telephone Number) - The number that is regarded as the billing account number on a phone bill. Sometimes when a customer calls a phone company for service, the customer-service representative will ask the customer for the billed telephone number because that is the number that all the other customer's phone numbers and charges are referenced to. This method is used so that a customer doesn't get a phone bill for every individual phone line they have.

BTS (Base Transceiver Station) - A station that transmits mobile radio signals.

Buffer - A temporary storage (memory) device for data. A buffer is basically a box with RAM inside it. A common application for buffers is to collect a stream of data and temporarily store it until another device, such as a PC or server asks the buffer to download it. This is useful when the PC, server or LAN could be out of service for a period of time. When the server or PC is returned to service it just asks for the data from the buffer and it is downloaded. The buffer is then empty and ready to receive more data.

Building Entrance Agreement A building entrance agreement gives a telephone company or other utility the privilege to construct communications facilities into a building and to occupy their own space for equipment, power for the equipment, and access to said equipment. Even though having a CLEC present in a building is a great advantage for tenants, smart building management companies use their position to an advantage. They only allow the CLEC to construct the facilities into the building the way they want, when they want. The facilities (fiber, cable, conduit, not electronics) when completed belong to the building. In some cases, the building management then charges rent back to the CLEC for the use of the facilities that they paid to have designed and constructed. The CLECs must agree to all of the building management's terms because without building entrance agreements the CLECs can only exist by using another phone companies facilities (usually an RBOCs) to provide service.

Building Industry Consulting Service International (BICSI) - The provider of the RCDD (Registered Communications Distribution Designer) certification. The RCDD certification is often referred to as a BICSI (pronounced "bik-see") certification. The RCDD certification is designed to educate professionals in the area of physical network distribution, including twisted pair and optical media. More information can be found regarding BICSI certifications at http:// www.bicsi.org.

Bulletin Board System (BBS) - A Website accessed by users that acts as a central source of information. BBS Websites are usually set up by particular interest category.

Buried Cable Terminal - Where buried service wires are fed from between the feeder cable and the standard network interface. For a photo of a Buried Terminal, see Pedestal. Buried Service Wire Splice - A special watertight splice that is filled with an encapsulant. Common types of these splices are made by Keptel and Communications Technology Corporation .

Bus Topology - A LAN physical topology, which means the way that the individual devices within the LAN are physically connected .The method at which the devices connected to the LAN access the media (coax is common for this topology) is called the logical topology. The bus topology is a wire (UTP) that behaves as a street that connects a number of PCs. When a PC wants to access the network or wire to a server or another PC, it looks at the street to see if there is no traffic. If there is no traffic, then the PC (or server) sends data down the wire (or street). The data has an address attached to it and all the other devices connected to the network see the address. If the address belongs to a certain device, that device reads the data attached to the address. This scheme of sending data is called Ethernet. One of the inefficiencies of Ethernet is something called a collision. A collision happens when two or more devices look at the network (the wire) and see that it is clear at the same time, then attempt to send data at the same time. The data that is transmitted by the multiple devices collides and becomes corrupted. The devices on the network sense the collision and try to send their data again when the network is clear. This method of control is classified as a contention-based protocol because all the devices on the network contend for its use. All of the Ethernet protocols are contention based. See also CSMA/CD, CSMA/CA, and Ring Topology.

Busy Hour - The hour in the day or month when a central office or PBX connects the most calls. The busy hour is an important factor in designing a switch for blocking.

Busy Lamp Field - The lights on an attendant console that indicate who is on their line (what lines are busy) and who is not. Some busy lamp fields are an add-on module that can be attached to a phone.

Busy Out - A temporary fix or condition of a phone service. To "busy a line out of a hunt sequence." If a business phone line becomes defective and it is in a hunt or roll over sequence, calls will not hunt or roll past this line. Say that you have four lines coming into your business. The first line is the main number and if that first line is busy, then calls come in on the second line, etc. If line one goes bad then it can't be called, so it can't be busy. Because it is not busy, then calls will not hunt or rotate to the next three lines. When you call the phone company repair service they busy out the bad line, which makes it look busy to the network. Your calls then start coming in on the other three lines. When a repair technician finishes with repairing the problem on the bad line, he has it unbusied.

Busy Override - When an attendant or operator adds themselves on to a line that is already in use. This is also called a "barge in." If a local phone company operator barges in on a phone conversation the people on the line will hear a beep tone, then subsequent short beep tones as long as the operator is connected. The operator can converse with the two parties on the line after barging in and pass on urgent information. This is a common feature of PBX systems. A PBX system can be programmed to not warn the people in the middle of their call that another person is listening. This feature is often used to monitor the quality of customer service in call centers.

Busy Signal - There are two types of busy signals. The most common type is a slow busy, which means that the number you are trying to call is being used. The other type of busy signal is a fast busy, which means the phone company central office could not understand the digits that you dialed or the actual phone network is too busy to take your call. Many fast busy signals are being replaced with "intercept messages," which tell the dialer what the problem is. Examples of intercept messages are: "I'm sorry, all circuits are busy now. Please try your call again later." And "The number dialed is out of service. Please check the number and try your call again".

Busy Verification - The local telephone company test to see if a particular phone number (or circuit, or loop as they call them) is busy. The test is run by a DATU (Direct Access Test Unit) in the central office. When the test comes back, it says the line is "in use busy speech" or "ROH (Ringer Off Hook)," which means that the handset has been taken off the hook and left there.

Butt Set (slang) - A test telephone set used by telephone installation and repair personnel. Instead of a plug on the end of the cord, it has a pair of alligator/bed-of-nails clips. For a photo, see Craft Test Set.

Bypass Trunk Group - A method of connecting one central office to another without going through a tandem. This method reduces tandem traffic and reduces blockage between the two offices that have bypass trunk groups installed.

Byte - Eight bits, also known as an octet.

Byte-Oriented Protocol - An older class and "era" of data-link communications transmission rules that use a specific character from a character set code (ASCII or EBCDIC) to delimit or separate transmitted frames. These protocols have been almost completely replaced by bit-oriented protocols. Byte-oriented methods are avoided when possible. Even less technologically advanced parts of the world have migrated to bit- oriented protocols, such as X.25.

Byte Reversal An electronic logic process used in Intel microprocessors. It stores least-significant integer and address bits first. See also LSB

Byte Stuffing Byte stuffing is what some communications protocols do to make data more suitable for transmission. If a customer wants to send 30 bytes, but one transmission frame carries 48 bytes, then the transmission equipment adds 18 bytes so that the frame is full. Think of byte stuffing as the styrofoam peanuts or wadded-up paper you put in a box when you ship something through the mail.