B8ZS (Bipolar 8 Zero Substitution) - a technique used to satisfy the ones density requirements of digital T-carrier facilities in the public network while allowing 64 Kbps clear channel data. Strings of eight consecutive zeroes are replaced by an eight-bit code representing two intentional bipolar pulse code violations (000V10V1).

Backbone - The main connectivity device of a distributed system. All systems that have connectivity to the backbone connect to each other. This does not stop systems from setting up private arrangements with each other to bypass the backbone for cost, performance, or security.

Background Noise - The total system noise in the absence of information transmission, independent of the presence or absence of a signal.

Backplane - High-speed communications line to which individual components are connected. In multi-plane fabric switches, the backplane allows for inter-fabric connections and timing distribution without the need for physical cables.

Baffle - A mounting board or screen which separates acoustic power at the back of a loudspeaker cone from the power directly emitted from the front of the loudspeaker. Baffles improve bass response by increasing the length of the path difference between the two sources of sound. Also, a heat displacing device mounted between equipment in a rack or enclosure to direct heat from a unit away from equipment mounted above it.

Bandwidth - Usually identifies the capacity or amount of data that can be sent through a given circuit; may be user-specified in a PVC.

Bar Code - Lines of varying width printed on the label of a product. The bar code is designed to be read optically by a data capturing device.

Bare Wire - Uninsulated wire.

Battery or Batteries - A DC voltage source made up of one or more cells that convert chemical energy into electrical power. The combination of several cells is more correctly referred to as the battery (singular). The cells themselves are sometimes erroneously referred to as batteries.

Battery Acid - Dilute sulfuric acid used as electrolyte in a lead/acid storage battery/accumulator.

Battery Alarm - Alarm indicating that there is a fault in a main battery circuit.

Battery Backup - A battery which provides power to equipment during the absence of commercial AC.

Battery Capacitance - The capacitance of a battery plant which acts as a filter.

Battery Eliminator - A device which has a rectifier and a filter. This device will convert AC power into the correct DC voltages necessary to drive a telephone system. Such a battery eliminator or power supply should deliver “clean” power, i.e. with little “noise” and of low impedance.

Battery Noise - Noise which is sometimes fed into telephone circuits on the DC power supply leads, e.g. a low hum from the rectifier or impulse noise from relay contact circuits.

Battery Pair - A pair of wires used to carry DC power which is tapped from the central office storage battery.

Battery Reserve - The length of time for which a storage battery can provide DC power within the circuit voltage limits of the load equipment.

Battery Separator - Sheets of nonconducting porous material between positive and negative plates in a storage battery. They prevent short circuits caused by plates bending and touching.

Battery Stand or Rack - A rigid structure used to accommodate a group of cells. Available for different seismic zones.

Battery String or Battery Plant - A DC voltage source made up of one or more cells that convert chemical energy into electrical power.

Baud - Unit of signaling speed. The speed in baud is the number of discrete conditions or signal events per second. If each signal event represents only one bit, the baud rate is the same as bps; if each signal event represents more than one bit (such as a digit), the baud rate is smaller than bps.

BBC (Broadband Bearer Capability) - Indicates request for connection-oriented service that will provide interworking (i.e. DS1 emulation) ATM only, or VP service (for switched VPs).

“B” Carrier - See Wireline Cellular Company.

BCOB (Broadband Connection Oriented Bearer) - Information in the SETUP message that indicates the type of service requested by the calling user.

BCOB-A (Bearer Class A) - Indicated by ATM end user in SETUP message for connection-oriented, constant bit rate service. The network may perform internetworking based on AAL information element (IE).

BCOB-C (Bearer Class C) - Indicated by ATM end user in SETUP message for connection-oriented, variable bit rate service. The network may perform internetworking based on AAL information element (IE).

BCOB-X (Bearer Class X) - Indicated by ATM end user in SETUP message for ATM transport service where AAL, traffic type and timing requirements are transparent to the network.

BD or BOD (Battery On Discharge) - A discrete lead designation used to report a low battery voltage condition. Initiation of the alarm is usually taken from the LV1 Lorain Products plant setting. The low float setting on WECO coded plants that have this feature can also be used for this alarm. The 326 and 111A coded plants, designed to serve the ESS switching system, are arranged with a standard option to provide this feature. The signal is taken from the higher level of a low voltage battery condition and is used to forward an early warning that the batteries are low, which implies that the batteries are being used to provide a part or all of the plant demand.

BDCBB (Battery Distribution Circuit Breaker Board - A bay containing panels equipped with circuit breaker arrangements that distribute 24 volt or 48 volt battery.

BDFB (Battery Distribution Fuse Board - A frame that accepts feeders from 24, 48, or 130 volt battery plants and distributes the power through branch fuses to the load. It is usually located near the equipment it serves.

BECN (Backward Explicit Congestion Notification) - A Resource Management (RM) cell type generated by the network or the destination, indicating congestion or approaching congestion for traffic flowing in the direction opposite that of the BECN cell.

Benchmark - A standardized task to test the capabilities of various devices or organizations against each other for performance.

Bending Radius - The minimum allowable curvature of a cable before it is damaged. Very critical in all aspects of cable laying, especially with under-carpet cabling and fiber optic cable.

BER (Bit Error Rate) - A measure of transmission quality. It is generally shown as a negative exponent, (e.g., 10-7 which means 1 out of 107 bits are in error or 1 out of 10,000,000 bits are in error).

BES (Bursty Errored Seconds) - a BES contains more than 1 and fewer than 320 path coding violation error events, and no severely errored frame or AIS defects. Controlled slips are not included in determining BESs.

Beta Test - Typically the last step in the testing of a product before it is officially released. A beta test is often conducted with customers in their offices.

BGP (Border Gateway Protocol) - Used by gateways in an internet connecting autonomous (router) networks. It is defined in RFC 1771.

B-ICI (B-ISDN Inter-Carrier Interface) - An ITU-T defined specification for broadband switched virtual connection between public networks.

Binary - A number system where only two values or states are possible for a particular condition, such as “ON” and “OFF” or “One” and “Zero.”

BIP (Bit Interleaved Parity) - An error-detection technique in which character bit patterns are forced into parity, so that the total number of one bits is always odd or always even. This is accomplished by the addition of a one or zero bit to each byte, as the byte is transmitted; at the other end of the transmission, the receiving device verifies the parity (odd or even) and the accuracy of the transmission.

B-ISDN (Broadband Integrated Services Digital Network) - A common digital network suitable for voice, video, and high-speed data services running at rates beginning at 155 Mbps.

B-ISUP (Broadband ISDN User’s Part) - A protocol used to establish, maintain and release broadband switched network connections across a SS7/ATM network.

Bit - Abbreviation for binary digit. A single binary digit of information represented as a 0 (zero) or 1 (one).

Bit Robbing - The use of the least significant bit per channel in every sixth frame for signaling.

BITS (Building Integrated Timing Supply) - The BITS is the master timing supply for an entire building, which is a master clock and its ancillary equipment. The BITS supplies DS1 and/or composite clock timing references for synchronization to all other clocks and timing sources in that building.

Bit Stuffing - A process in bit-oriented protocols where a zero is inserted into a string of ones by the sender to prevent the receiver from interpreting valid user data (the string of ones) as control characters (a Flag character for instance).

Blackout - A close down of radio communications for security purposes. Also, a fade-out of radio communications caused by ionospheric activity. Also, a complete loss of electrical power.

Block Diagram - A graphic way to show different elements of a program or process by the use of squares, rectangles, diamonds, and various shapes connected by lines to show what must be done, when it must be done, and what happens if it’s done this way or that.

BN - A bit used to identify whether an RM cell is Backward Explicit Congestion Notification cell or not.

BNC (Bayonet-Neill-Concelman) - A bayonet-locking connector used to terminate coaxial cables. BNC is also referred to as Bayonet Network Connector.

BOC or RBOC (Bell Operating Company) - The 22 regulated telephone companies of the former Bell System, which was broken apart by divestiture. These companies were grouped into seven Regional Holding Companies (RHCs). According to the terms of divestiture, these companies must limit their activities to local telephone service, directory service, customer premise equipment, cellular radio and any other ventures that the Federal Court may approve from time to time.

Border Node - A logical node that is in a specific peer group, and has at least one link that crosses the peer group boundary.

BPDU (Bridge Protocol Data Unit) - A message type used by bridges to exchange management and control information.

bps (Bits per Second) - A measure of speed in a serial transmission.

BPV (Bipolar Violation) - an error event on a line in which the normal pattern of alternating high (one) and low (zero) signals is disrupted. A bipolar violation is noted when two high signals occur without an intervening low signal, or vice versa.

Breadboard - A circuit board that is made by hand, usually in building a prototype.

Break Contacts - Contacts which open when a relay is operated or a key thrown.

Bridge - a device that expands a Local Area Network by forwarding frames between data link layers associated with two separate cables, usually carrying a common protocol. Bridges can usually be made to filter certain packets (to forward only certain traffic).

Bridge Rectifier - A full-wave rectifier with four rectifying units arranged in a bridge so that when AC is connected across one diagonal, DC is available across the other diagonal.

Broadband - a service or system requiring transmission channels capable of supporting rates greater than the Integrated Services Digital Network (ISDN) primary rate.

Broadband Access - an ISDN access capable of supporting one or more broadband services.

Broadcast - Data transmission to all addresses or functions.

Brouter (bridging/router) - a device that routes some protocols and bridges others based on configuration information.

Brownout - A reduction in commercial voltage level that may be a result of an overload on the system.

BSP (Bell System Practice) - A standard or procedure specified by the Bell System.

B-TE (Broadband Terminal Equipment) - An equipment category for B-ISDN which includes terminal adapters and terminals.

Buffer - A data storage medium used to compensate of a difference in rate of data flow or time of occurrence of events when transmitting data from one device to another.

Building Alarms - The group of alarms in a central office which cover alarm conditions for such items as sump pumps, air dryers, heating and air conditioning.

Burn-In - To run new devices and printed circuit cards, often at high temperatures, in order to pinpoint early failures.

Bursty Second - A second during which there were at least the set number of BES threshold event errors but fewer than the set number of SES threshold event errors.

BUS (Broadcast and Unknown Server) - in an emulated LAN, the BUS is responsible for accepting broadcast, multicast, and unknown unicast packets from the LECs to the broadcast MAC address (FFFFFFFFFFFF) via dedicated point-to-point connections, and forwarding the packets to all of the members of the ELAN using a single point-to-multipoint connection.

Bus Bar - Copper or aluminum bars used to transmit or terminate AC or DC power.

Busy Hour Drain - The average amount of current required by connected telephone equipment over a period of one hour at the time of maximum use.

Busy Tone - Low tone, interrupted once per second, indicating that the called line is busy.

Bypass - Descriptive of an inverter plant status whereby the normal input source is transferred through a static or mechanical switch to the alternate source.

Bypass Cabling - Bypass cabling or relays are wired connections in a local area ring network that permit traffic to travel between two nodes that are not normally wired next to each other.

Byte - A computer-readable group of bits (normally 8 bits in length).