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Technology Glossary


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Select a letter above to access the technology glossary in alphabetical order.
Select + for miscellaneous.

Cable - A single wire or group of individual wires in a single sheath.

Cable Box - Box where cables are terminated.

Cable Clamp - Clamp used to secure cables in position on a surface.

Cable Rack - Framework fastened to bays to support and route cabling between bays.

Cable Riser - Cable running vertically in a multi-story building to serve the upper floors.

Cable Run - Conduit used to run cables through a building. Also the path taken by a cable or group of cables.

Cable Shield - A metallic component of the cable sheath which prevents outside electrical interference and drains off current induced by lightning.

Cable Splice - (1) The connection of two pieces of cable by joining them mechanically; (2) in submarine operations, connection of two pieces of cable including the armor wires (as distinct from a cable joint which connects only the core).

Cable Tray - Steel trough erected above equipment racks to support cable runs in an equipment room.

Cable Vault - Room under the main distribution frame in a central office. Cables from the subscribers’ lines come into the building through the cable vault.

CAC (Connection Admission Control) - The procedure used to decide if a request for an ATM connectioncan be accepted based on the attributes of both the requested connection and the existing connections.

Cache - Cache memory is used by the CPU. It contains the set of instructions next to be executed.

Cache Imposition Requests - Generated by the egress MPS and sent to the egress MPC to determine if the MPC can support a shortcut.

CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) - Hardware and/or software used as an aid in the design process and computerized control of manufacturing.

Calcium Battery - A lead-acid cell using lead-calcium alloy plates.

Calibrate - To test and reset a measuring or timing device against some standard to make sure it is functioning correctly.

Calibration - The process of identifying, measuring, and correcting errors in instruments and/or procedures.

Call - An association between two or more users or between a user and a network entity that is established by the use of network capabilities. This association may have zero or more connections.

Call-Back - In data transmission, a facility which enables the originator of a call attempt to a busy terminal to request the network to establish the call when the busy terminal becomes free.

CAP (Customer Administration Panel) - A simplified alternative to CAC, which is Customer Administration Center. These are AT&T terms.

Capacitance - The capacity of a media (wire, cable, resistor, bus) to store an electrical charge. Capacitance is measured in farads.

Capacitor - A device which introduces capacitance into an electric circuit.

Capacitor-Input Filter - Common type of smoothing filter; output from a rectifier is shunted by a large capacitor as the first element in a smoothing circuit.

Carrier - A company, such as any of the "baby Bell" companies, that provide network communications services, either within a local area or between local areas.

Cartridge Fuse - Type of fuse with the fusible wire enclosed within a short tube of glass or fiber with metal caps on both ends.

Catastrophic Failure - Complete and sudden failure of a system.

CAS (Channel Associated Signaling) - A form of circuit state signaling in which the circuit state is indicated by one or more bits of signaling status sent repetitively and associated with that specific circuit.

CATV - May mean either Community Antenna TeleVision or CAble TeleVision. CATV is a broadband transmission facility and generally uses a 75-ohm coaxial cable.

CBDS (Connectionless Broadband Data Service) - A connectionless service similar to Bellcore’s SMDS defined by European Telecommunications Standards Institute (ETSI).

CBR (Constant Bit Rate) - A type of traffic that requires a continuous, specific amount of bandwidth over the ATM network (e.g., digital information such as video and digitized voice).

CBR port - a port on the CellPath 300 for transmitting and receiving CBR traffic.

cchan - A Marconi program used to manage virtual channels on a Marconi ATM switch running asxd.

CCITT (International Telephone and Telegraph Consultative Committee) - the international standards body for telecommunications.

CCS (Common Channel Signaling) - A form signaling in which a group of circuits share a signaling channel. Refer to SS7.

CCS (Common Channel Signaling) - A form signaling in which a group of circuits share a signaling channel. Refer to SS7.

CDF (Cutoff Decrease Factor) - For ABR, controls the decrease in Allowed Cell Rate (ACR) associated with the count of forward RM-cells sent without a received backward RM-cell (0 range of 1/64 to 1 with 1/16 as the default).

CDMA (Code Division Multiple Access) - A form of modulation whereby digital information is encoded in an expanded bandwidth format. Several transmissions can occur simultaneously within the same bandwidth with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission. It permits a high degree of energy dispersion in the emitted bandwidth.

CDO (Community Dial Office or Codial Office) - A small, automatic, central office switching system that is completely unattended.

CDV (Cell Delay Variation) - a quantification of cell clumping for a connection. The cell clumping CDV (yk) is defined as the difference between a cell's expected reference arrival time (ck) and its actual arrival time (ak). The expected reference arrival time (ck) of cell k of a specific connection is max . T is the reciprocal of the negotiated peak cell rate.

CDVT (Cell Delay Variation Tolerance) - Used in CBR traffic, it specifies the acceptable tolerance of the Cell Delay Variation (CDV) (jitter).

CE (Connection Endpoint) - A terminator at one end of a layer connection within a SAP.

CEI (Connection Endpoint Identifier) - An identifier of a CE that can be used to identify the connection at a SAP.

Cell - An ATM Layer protocol data unit (PDU). The basic unit of information transported in ATM technology, each 53-byte cell contains a 5-byte header and a 48-byte payload.

Cell Delineation - The process for recognizing the beginning and end of ATM cells within the raw serial bit stream.

Cell Header - The five bytes of control information found in each ATM cell.

Cell Loss Ratio - In a network, cell loss ratio is (1-x/y), where y is the number of cells that arrive in an interval at an ingress of the network; and x is the number of these y cells that leave at the egress of the network element.

Cell Port - A port on the CellPath 300 that transmits and receives traffic in cell format.

Cell Rate Adaptation - A function performed by a protocol module in which empty cells(known as unassigned cells) are added to the output stream. This is because there always must be a fixed number of cells in the output direction; when there are not enough cells to transmit, unassigned cells are added to the output data stream.

Cell Splitting - A means of increasing the capacity of a cellular system by subdividing or splitting cells into two or more smaller cells.

Cell Tagging - A Tag or Mark is used to distinguish lower priority cells from higher or guaranteed cells in the same data flow. CLP=0 cells when tagged become CLP=1 cells.

Cell Transfer Delay - The transit delay of an ATM cell successfully passed between two designated boundaries. See CTD.

Cellular Radio - A mobile radio system in which an area is broken up into cells. Every cell is handled by one transceiver (receiver/transmitter). As a cellular mobile radio moves from one cell to another, it is “handed off” to the next cell by a master computer, which determines from which cell the signal is strongest.

CEMF (Counter EMF Cells) - A semiconductor device connected in series with a battery and used to reduce the voltage to loads that cannot tolerate the “normal” main cell float voltage. Additional battery reserve time is obtained by the use of extra battery and CEMF cell(s). The CEMF cells are automatically switched out of the circuit when the discharge voltage decreases to a predetermined level and are automatically switched back into the circuit when the battery voltage approaches its normal float value. May also be used to reduce the load voltage when the batteries are being equalized.

Central Office - A phrase used to describe a building facility housing telephone equipment used to switch telephone traffic between calling and called parties. Sometimes referred to as switching center, exchange, community dial office, etc.

Central Office Battery - A group of cells joined in series to provide typically 48 volts DC. Central office batteries are typically charged off the main AC source and have two functions: (1) provide a constant source of DC power for 8 hours or so after AC power drops, and (2) isolate the central office from glitches on the AC line.

Central Office Equipment - Apparatus, including switching, power, and signaling equipment, installed in a central office.

Central Office Protector - Devices on the main distribution frame of a central office to provide protection against high voltage and high currents and against currents which are too low to blow fuses but which would be harmful if continued for long periods. Typically these are heat coils, delayed action fuses, or solid state devices.

CES (Circuit Emulation Service) - The ATM Forum circuit emulation service interoperability specification specifies interoperability agreements for supporting Constant Bit Rate (CBR) traffic over ATM networks that comply with the other ATM Forum interoperability agreements. Specifically, this specification supports emulation of existing TDM circuits over ATM networks.

CGA (Carrier Group Alarm) - A service alarm generated by a channel bank when an out-of-frame (OOF) condition exists for some predetermined length of time generally 300 milliseconds to 2.5 seconds). The alarm causes the calls using a trunk to be dropped and trunk conditioning to be applied.

CGSA (Cellular Geographic Service Area) - The actual area in which a cellular company provides cellular service. This area may be somewhat smaller than the Metropolitan Statistical Area surrounding it.

Channel - A path or circuit along which information flows.

Channel Bank - A device that multiplexes many slow speed voice or data conversations onto high speed link and controls the flow.

Channelization - Capability of transmitting independent signals together over a cable while still maintaining their separate identity for later separation.

Charge - (1) To replenish or replace the electrical charge in a secondary cell or storage battery; and (2) to store electrical energy in a capacitor.

Charger-Eliminator - A battery eliminator; a rectifier which provides low noise, low impedance DC output which can be used to power a PBX without the necessity of a storage battery.

Chargers (Rectifiers) - Electrical equipment used to change AC power to DC power and charge storage cells.

Charging Current - Current which flows in to charge a capacitor when it is first connected to a source of electric potential or the current flowing into a battery.

Charging Equipment - Rectifier or motor generator equipment used to convert AC power to DC power at voltages suitable for central office equipment and battery floating and charging.

Child Node - A node at the next lower level of the hierarchy that is contained in the peer group represented by the logical group node currently referenced. This could be a logical group node, or a physical node.

Child Peer Group - A child peer group of a peer group is any one containing a child node of a logical group node in that peer group. A child peer group of a logical group node is the one containing the child node of that logical group node.

Chip - The physical structure upon which integrated circuits are fabricated as components of telephone systems, computers, memory systems, etc.

Choke Input Filter - Low pass power smoothing filter with inductance as its first element.

CI (Congestion Indication) - When congestion is encountered, a switch sets the Congestion Indication (CI) bit in the forward RM cell. After being turned around by the destination, the now backward RM cell with the CI bit set causes the source to decrease its sending rate by some predefined percentage or amount.

CIP(Carrier Identification Parameter) - A 3 or 4 digit code in the initial address message identifying the carrier to be used for the connection.

CIR (Committed Information Rate) - CIR is the information transfer rate which a network offering Frame Relay Services (FRS) is committed to transfer under normal conditions. The rate is averaged over a minimum increment of time.

Circuit - A communications link between points.

Circuit Board - A board with microprocessors, transistors and other small electronic components (same as Printed Circuit Board).

Circuit Breaker - A device designed to safely open and close a circuit and protect it from overloads. The device automatically opens the circuit when a predetermined voltage or current occurs.

Circuit Schematic Drawing - Electrical diagram of an electrical or electronic device.

Circuit Voltage Limits - The operational window of electrical circuits or equipment.

Clamp-On Ammeter - An ammeter which does not have to be inserted in the circuit in order to measure the flow through the meter.

CLS (Connectionless service) - A service which allows the transfer of information among service subscribers without the need for end-to-end establishment procedures.

CLIP (Classical IP) - IP over ATM which conforms to RFC 1577.

Clocking - Regularly timed impulses.

Closed User Group - A subgroup of network users that can be its own entity; any member of the subgroup can only communicate with other members of that subgroup.

CLP (Cell Loss Priority) - The last bit of byte four in an ATM cell header; indicates the eligibility of the cell for discard by the network under congested conditions. If the bit is set to 1, the cell may be discarded by the network depending on traffic conditions.

CLR (Cell Loss Ratio) - CLR is a negotiated QoS parameter and acceptable values are network specific. The objective is to minimize CLR provided the end-system adapts the traffic to the changing ATM layer transfer characteristics.

The Cell Loss Ratio is defined for a connection as: Lost Cells/Total Transmitted Cells. The CLR parameter is the value of CLR that the network agrees to offer as an objective over the lifetime of the connection. It is expressed as an order of magnitude, having a range of 10-1 to 10-15 and unspecified.

C Message Weighting - A factor in noise measurements to approximate the lesser annoying effect on the human ear of high- and low-frequency noise compared to mid-range noise.

CMIP (Common Management Interface Protocol) - An ITU-TSS standard for the message formats and procedures used to exchange management information in order to operate, administer maintain and provision a network.

CMR (Cell Misinsertion Rate) - The ratio of cells received at an endpoint that were not originally transmitted by the source end in relation to the total number of cells properly transmitted.

Coaxial Cable - Coax is a type of electrical communications medium used in the LAN environment. This cable consists of an outer conductor concentric to an inner conductor, separated from each other by insulating material, and covered by some protective outer material.

This medium offers large bandwidth, supporting high data rates with high immunity to electrical interference and a low incidence of errors. Coax is subject to distance limitations and is relatively expensive and difficult to install.

Cold Start Trap - a CellPath 300 SNMP trap which is sent when theunit has been power-cycled (see trap).

CO-Located - Equipment located with the PBX.

Co-Located - (1) In the same building; and (2) separated by not more than 25 ohms of cable.

Collision - Overlapping transmissions that occur when two or more nodes on a LAN attempt to transmit at or about the same time.

Commercial AC Failure - An alarm condition which will be present when the utility service to the building fails.

Commercial Power - The local electric utility AC power that normally supplies a building.

Commercial Power Failure - The condition when the commercial power source goes below a specified voltage limit.

Common Battery - A battery (or several batteries) that acts as a central source of energy for any similar pieces of equipment.

Common Peer Group - The lowest level peer group in which a set of nodes is represented. A node is represented in a peer group either directly or through one of its ancestors.

Comm Port - the front panel DCE port that allows access to the CellPath 300 user interface via a connected terminal.

Complex Node Representation - A collection of nodal state parameters that provide detailed state information associated with a logical node.

Compression Tap - Clamp used to connect a power lead to a main power conductor without breaking and terminating the conductor.

Concatenation - The connection of transmission channels similar to a chain.

Concentrator - a communications device that offers the ability to concentrate many lower-speed channels into and out of one or more high-speed channels.

Conductor - Any device that can carry an electrical current.

Conduit - A device used to hold, organize, and protect electrical or optical cables.

Conduit Run - Route followed by cable conduits. Also called a duct run.

Configuration - The phase in which the LE Client discovers the LE Service.

Congestion Management - a CellPath 300 feature that helps ensure reasonable service for VBR connections in an ATM network. For each connection, the CellPath 300 maintains a priority, sustained cell rate (SCR), and peak cell rate (PCR). During times of congestion, the CellPath 300 reduces the bandwidth to the SCR, based on the priority of the connection.

Connecting Block - A device used to connect one group of wires to another.

Connection - the concatenation of ATM Layer links in order to provide an end-to-end information transfer capability to access points.

Connection Pacing - A mechanism in which Marconi System’s switches "pace" the SPVCs to ensure all do not flood the switch at the same time for the request for service.

Connection Scope - The level of routing hierarchy within which a given connection request to a group address is constrained.

Connectionless Service - a type of service in which no pre-determined path or link has been established for transfer of information, supported by AAL 4.

Connection-Oriented Service - A type of service in which information always traverses the same pre-established path or link between two points, supported by AAL 3.

Connectivity - The ability of a device to communicate with other devices through a communications facility.

Contactor - An alarm unit used in cable pressurization schemes which activates when there is a fall in pressure. Also a large mechanical relay used to open or close electrical circuits.

Controlled Rectifier - Rectifier utilizing silicon controlled rectifier elements.

Controlled Slip - A situation in which one frame's worth of data is either lost or replicated. A controlled slip typically occurs when the sending device and receiving device are not using the same clock.

Controller - Universally defined as a device which automatically regulates a machine. Specifically, given in this context to address Lorain Products S.M.A.R.T.® controller, which is designed to monitor voltages, amperes, and alarms with a screen display feature, as well as an automatic remote reporting feature. The controller will also control the 48V plant with which it is associated.

Converter - Electrical apparatus or equipment that converts one level or polarity of DC voltage to another level or polarity.

Converter Fail (MJ) - An alarm condition generated by converter plants to announce the failure of more than one converter. Normally connected as a major alarm.

Converter Fail (MN) - An alarm condition generated by converter plants to reflect the failure of one converter. Normally connected as a minor alarm.

Converter Plant - A combination of equipment typically consisting of multiple converters, alarms, meters, and distribution fuses or circuit breakers.

Corresponding Entities - Peer entities with a lower layer connection among them.

CP-AAL (Common Part AAL (ATM Adaptation Layer)) - The common part protocol (specified as AAL5 in I.363) provides information transfer and a mechanism for detecting corrupted SDUs.

cpath - A Marconi program used to manage virtual paths on a Marconi ATM switch running asxd.

CPE (Customer Premise Equipment) - Equipment that is on the customer side of the point of demarcation, as opposed to equipment that is on a carrier side. See also point of demarcation.

cport - A Marconi program used to monitor and change the state of ports on a Marconi ATM switch running asxd.

CPU (Central Processing Unit) - The part of a computer which has the logic, computational and decision-making hardware. It interprets and executes instructions as they are received.

Crankback - A mechanism for partially releasing a connection setup in progress that has encountered a failure. This mechanism allows PNNI to perform alternate routing.

CRC (Cyclic Redundancy Check) - an error detection scheme in which a number is derived from the data that will be transmitted. By recalculating the CRC at the remote end and comparing it to the value originally transmitted, the receiving node can detect errors.

Crimp Termination - A terminal connected to a conductor by high pressure crimping of wire into a lug.

CRM (Cell Rate Margin) - Measure of difference between effective bandwidth allocation and the allocation for substantial cell rate.

Cross Connection - A mapping between two channels or paths at a network device such as the CellPath 300.

CRS (Cell Relay Service) - A carrier service which supports the receipt and transmission of ATM cells between end users in compliance with ATM standards and implementation specifications.

CRT (Cathode Ray Tube) - A vacuum tube containing an electron gun which directs a beam on the coated front inside of the tube. A TV screen.

CS (Convergence Sublayer) - a portion of the AAL. Data is passed first to the CS where it is divided into rational, fixed-length packets or PDUs (Protocol Data Units). For example, AAL 4 processes user data into blocks that are a maximum of 64 kbytes long.

CSU (Channel Service Unit) - An interface for digital leased lines which performs loopback testing and line conditioning.

CT (Current Transformer) - An instrument transformer inserted in a power circuit for metering or controlling the line current. The transformer ratio is generally arranged to have 5 amperes in the secondary when full load current flows.

CTD (Cell Transfer Delay) - This is defined as the elapsed time between a cell exit event at the measurement point 1 (e.g., at the source UNI) and the corresponding cell entry event at the measurement point 2 (e.g., the destination UNI) for a particular connection. The cell transfer delay between two measurement points is the sum of the total inter-ATM node transmission delay and the total ATM node processing delay.

CTS (Clear To Send) - and RS-232 modem interface control signal (sent from the modem to the DTE on pin 5) which indicates that the attached DTE may begin transmitting; issuance in response to the DTE's RTS.

Current - A measure of how much electricity passes a point on a wire in a given time frame. Current is measured in amperes.

Current Limiting - A control circuit action that limits the output current of a constant voltage power supply to some predetermined maximum value (fixed or adjustable) when an overload or short circuit occurs. Usually, the output voltage is automatically restored to its normal value when the overload or short circuit is removed.

Current-Limiting Resistor - Resistor inserted in a circuit for security or safety reasons which limits the value of the current which would flow under fault conditions.

Cursor - Transparent slide or sheet used with radar displays or with calculating slide rules to give base position or location; also used with computer or word processor input devices on a video display unit to indicate where the next keyboard character will be entered.

Cut Through - Establishment of a complete path for signaling and/or audio communications.

Cycle - One complete sequence of an event or activity. Often refers to electrical phenomena. One electrical cycle is a complete sine wave.

Cylindrical Cells (also known as Round Cells) - Coded as KS-20472 battery cells by Western Electric, each cell is a round plastic jar with conically-shaped, horizontally stacked grids with lectrolyte.