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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.

Lace - To arrange cables in neat bundles, carefully laced together with nylon or lacing twine.

Lacing Cord (Lacing Twine) - Narrow ribbon of nylon used to lace cables in offices.

Lagging Current (Lagging Power Factor) - The condition in an inductive circuit whereby an alternating current wave lags the corresponding voltage wave.

Lagging Load - A load whose inductive reactance exceeds its capacitive reactance; when an alternating voltage is applied, the current lags behind the voltage.

LAN (Local Area Network) - A data network intended to serve an area of only a few square kilometers or less. Because the network is known to cover only a small area, optimizations can be made in the network signal protocols that permit higher data rates.

LAN Access Concentrator - A LAN access device that allows a shared transmission medium to accommodate more data sources than there are channels currently available within the transmission medium.

LANE (LAN Emulation) - A program that provides control over the execution of the LAN Emulation Server (LES), Broadcast/Unknown Server (BUS), and LAN Emulation Configuration Server (LECS) on the local host.

Landline - A telephone circuit that travels over terrestrial circuits, be they wire or microwave.

LAPB (Link Access Procedure, Balanced) - Data link protocol in the X.25 protocol stack. LAPB is a bit-oriented protocol derived from HDLC. See also HDLC and X.25.

LATA (Local Access and Transport Area) - Geographic boundaries of the local telephone network, specified by the FCC, in which a single LEC may perform its operations. Communications outside or between LATAs are provided by IXCs.

Latency - The time interval between a network station seeking access to a transmission channel and that access being granted or received.

Layer Entity - An active layer within an element.

Layer Function - A part of the activity of the layer entities.

Layer Service - A capability of a layer and the layers beneath it that is provided to the upper layer entities at the boundary between that layer and the next higher layer.

Layer User Data - The information transferred between corresponding entities on behalf of the upper layer or layer management entities for which they are providing services.

Layout A proposed or actual arrangement or allocation of equipment.

LBO (Line Build Out) - Because T1 circuits require the last span to lose 15-22.5 dB, a selectable output attenuation is generally required of DTE equipment (typical selections include 0.0, 7.5 and 15 dB of loss at 772 KHz).

LCD (Liquid Crystal Display) - An alphanumeric display using liquid crystal sealed between two pieces of glass.

LCV (Line Code Violations) - Error Event. A Line Coding Violation (LCV) is the occurrence of either a Bipolar Violation (BPV) or Excessive Zeroes (EXZ) Error Event.

le - A Marconi program that implements both the LAN Emulation Server (LES) and the Broadcast/Unknown Server (BUS).

Lead-Acid Battery - A rechargeable secondary cell used in central offices.

Lead-Acid Storage Cell - An individual cell used in central office batteries. The plates are made of lead, lead-antimony or lead-calcium and the electrolyte is dilute sulfuric acid. The charge/discharge action is reversible; cells may be charged and discharged many times or kept “floating” in a fully charged condition. Nominal voltage is 2 volts per cell, rising to 2.15 if fully charged and falling to 1.85 volts when discharged.

Lead-Antimony Cell - A lead-acid storage cell with plates made of a lead-antimony alloy.

Lead-Calcium Cell - A lead-acid storage cell with lead-calcium alloy used for plates. These cells have a longer life than antimony cells if they are floated. They should not be used on a charge/discharge cycle basis.

Lead Designation - The name or label given to a lead used for identification purposes, usually given in alpha terms and abbreviated for the function of the lead (i.e. FA for fuse alarm, PF for power failure, RFA for rectifier failure alarm, etc.).

Leading Current - In a capacitive circuit, an alternating current leads the voltage which produces it.

Leadership Priority - The priority with which a logical node wishes to be elected peer group leader of its peer group. Generally, of all nodes in a peer group, the one with the highest leadership priority will be elected as peer group leader.

Leaky Bucket - An informal ATM cell policing term for the Generic Cell Rate Algorithm which in effect receives cells into a bucket and leaks them out at the specified or contracted rate (i.e. PCR).

LE_ARP (LAN Emulation Address Resolution Protocol) - A message issued by a LE client to solicit the ATM address of another function.

LEC (Local Exchange Company) - The local phone companies, which can be either a Bell Operating Company (BOC) or an independent (e.g. GTE), who provide local transmission services. Prior to divestiture, the LECs were called telephone companies or telcos.

lecs - A Marconi program that implements the assignment of individual LECs to different emulated LANs.

LECS (LAN Emulation Configuration Server) - The LECS is responsible for the initial configuration of LECs. It provides information about available ELANs that a LEC may join, together with the addresses of the LES and BUS associated with each ELAN.

LED (Light Emitting Diode) - A semiconductor diode which emits light when a current is passed through it.

leq - A Marconi program that provides information about an ELAN. This information is obtained from the LES, and includes MAC addresses registered on the ELAN together with their corresponding ATM addresses.

LES (LAN Emulation Server) - The LES implements the control coordination function for an ELAN. The LES provides the service of registering and resolving MAC addresses to ATM addresses.

Level - Level is the position in the PNNI hierarchy at which a particular node or peer group exists.

LGN (Logical Group Node) - An abstract representation of a lower level peer group as a single point for purposes of operating at one level of the PNNI routing hierarchy.

Life Cycle - Tests carried out to determine the probable useful life of similar equipment in normal working conditions.

Life Test - Test in which random samples of a product are tested to see how long they can continue to perform their functions satisfactorily. A special form of testing is used, usually with temperature or current or voltage or vibration effects cycled at many times the rate which would apply in normal usage.

Limiting - A process by which some characteristic at the output of a device is prevented from exceeding a predetermined value. Hard limiting is a limiting action with negligible variation in output in the range where the output is limited when subjected to a fairly wide variation of signal input. Soft limiting is a limiting action with appreciable variation in output in the range where the output is limited when subjected to a fairly wide variation of signal input.

Line Busy Tone - Busy tone. A low tone interrupted once per second indicating that the called line is busy.

Line Hit - Electrical interference that causes a hit, i.e. a loss or introduction of spurious bits into a data stream.

Line Loss - Total energy loss in a line.

Line to Line Voltage - The voltage between two phases of a 2 or 3 phase circuit or system.

Line to Neutral Voltage - The voltage between any of the hot lines and the neutral.

Line Voltage - Voltage of public power supplies, normally 117VAC in the U.S.

Link - An entity that defines a topological relationship (including available transport capacity)between two nodes in different subnetworks. Multiple links may exist between a pair of subnetworks. Synonymous with logical link.

Link Attribute - A link state parameter that is considered individually to determine whether a given link is acceptable and/or desirable for carrying a given connection.

Link Constraint - A restriction on the use of links for path selection for a specific connection.

Link Down Trap - A CellPath 300 SNMP trap that signifies that the Ethernet interface has transitioned from a normal state to an error state, or has been disconnected.

Link Layer - The layer in the OSI model regarding transmission of data between network nodes.

Link Metric - A link parameter that requires the values of the parameter for all links along a given path to be combined to determine whether the path is acceptable and/or desirable for carrying a given connection.

Link State Parameter - Information that captures an aspect or property of a link.

Link Up Trap - A CellPath 300 SNMP trap that signifies that the Ethernet interface has transitioned from an error condition to a normal state.

Live (1) Connected to a source of electric potential; and (2) acoustically reverberant.

LLC (Logical Link Control) - A protocol developed by the IEEE 802 committee for data-link-layer transmission control; the upper sublayer of the IEEE Layer 2 (OSI) protocol that complements the MAC protocol; IEEE standard 802.2; includes end-system addressing and error checking.

Load - The electrical power used by a device. In this case, the average rating in amperes of all pieces of the system totalled to determine the storage battery required.

Load Sharing - Two or more computers in a system that share the load during peak hours. During periods of non peak hours, one computer can manage the entire load with the other acting as a backup.

Load Sharing - In common channel signaling, a process by which signaling traffic is distributed over two or more signaling or message routes, in view of traffic equalization or security. Also, operating rectifiers in a mode that forces the individual rectifiers to accept an equal portion of the load.

Load Shedding - Automatic removal of low priority loads from a generating system when total load exceeds the available alternator capacity because of either an increase in high priority loads or the loss of one or more alternators.

Load Transfer - The transfer of signaling traffic from one signalling link to another in a common channel signaling system.

Local Alarms - A term intended to describe the alarm system within a Bell Central Office. The system alerts personnel within the building with audible sounding and visual indications that an alarm condition exists. The classification of the alarm is given, as well as visual indicators directed to the origination of the problem.

Local Battery - (1) In telegraphy, the battery that actuates the telegraphic station recording instruments, as distinguished from the battery furnishing current to the line; and (2) in telephony, a system where each telephone set has its own individual source of power.

Local Exchange - An exchange where subscribers’ lines are terminated.

Local Loop - The physical wires that run from the subscriber’s telephone set, PBX or key telephone system to the telephone company central office.

LOF (Loss Of Frame) - A type of transmission error that may occur in wide-area carrier lines.

Logical Group Node - A logical node that represents a lower level peer group as a single point for purposes of operating at one level of the PNNI routing hierarchy.

logical interface group - Used by Marconi ForeThought software for port numbering. Each port is recognized by fabric, logical interface group, and port number.

Logical Link - An abstract representation of the connectivity between two logical nodes. This includes individual physical links, individual virtual path connections, and parallel physical links and/or virtual path connections.

Logical Node - The lowest-level node or a logical group node.

Logical Node ID - A string of bits that unambiguously identifies a logical node within a routing domain.

Loop - (1) Go and return conductors of an electric circuit (a closed circuit); (2) a single connection from a switching center or an individual message distribution point to the terminals of an end instrument; (3) a closed path under measurement in a resistance test; (4) a type of antenna used extensively in direction finding equipment; (5) in computer systems, repetition of a group of instructions in a computer routine; and (6) in telephone systems, a pair of wires from a central office to the subscriber’s telephone.

Loopback - A troubleshooting technique that returns a transmitted signal to its source so that the signal can be analyzed for errors. Typically, a loopback is set at various points in a line until the section of the line that is causing the problem is discovered.

Loop Closure - A phrase which denotes a relay contact configuration which will complete a looped connection when the relay is in an alarm state. The lead designation will be paired with a return lead, the source of which is connected at the terminating portion of the circuit (the converse of grounded output).

Loop Length - The length of the electrical circuit between a power source and a piece of equipment and back.

looptest - A program that tests the interface for basic cell reception and transmission functionality. It is usually used for diagnostic purposes to determine if an interface is functioning properly.

Loop Voltage Drop - The difference of voltage at the transmitting and receiving ends of a loop.

LOP (Loss Of Pointer) - A type of transmission error that may occur in wide-area carrier lines.

LOS (Loss Of Signal) - A type of transmission error that may occur in wide-area carrier lines. The designation for a condition declared when the DTE senses a loss of a DS-1 signal from the CPE for more the 150 milliseconds (the DTE generally responds with an all ones "Blue or AIS" signal).

Loss - The drop in signal level between two points on a network. It is important to distinguish between loss and level. Level is measured at a finite point. Loss is the difference between levels. Loss occurs constantly throughout telephony, from long distance circuits to switches. Loss is usually measured in decibels (dB). Loss is cumulative. Add two circuits, each with a loss of 10 dB and you will have 20 dB loss in the total circuit. The human ear can detect a 3 dB loss.

Lowest Level Node - A leaf in the PNNI routing hierarchy; an abstraction representing a single instance of the PNNI routing protocol. Lowest-level nodes are created in a switching system via configuration. They are not created dynamically.

Low-High Voltage Alarm - An alarm indicating that a central office battery voltage is outside its permitted and preset range of values.

Low Tone - Tone of 480 Hz plus 620 Hz at -24dBm per frequency. Used for busy, reorder, and no-circuit tones.

Low Voltage Alarm - Alarm given when the battery string is discharged to below a predetermined voltage.

Low Voltage Disconnect - The low voltage disconnect circuit is a battery protection circuit designed to disconnect the loads from the battery plant & rectifier(s) in the event that the output voltage decreases below a predetermined voltage (normally 42.0VDC 1.75V/C), as during a commercial power failure or other fault condition where rectification is lost. When commercial power has been restored or the fault condition corrected and the battery voltage reaches 49VDC (adjustable), the low voltage disconnect circuit automatically reconnects the loads to the battery plant and rectifiers.

LSB (Least Significant Bit) - The lowest order bit in the binary representation of a numerical value.

Lug - A tag or projecting terminal onto which a wire may be connected by wrapping or soldering.

LV1 (Low Voltage) - A discrete lead designation connected to report a low voltage condition at the plant batteries at the minimum range. Can be used to report a low float condition as well as a battery on discharge situation. The alarm is usually considered a minor alarm and is connected as a grounded output or loop closure.

LV2 (Low Voltage) - A discrete lead designation indicative of a low voltage condition at the battery at the extreme allowable limit. The incidence of this alarm is classified as a major alarm. The alarm can be connected from an energized or de-energized relay, dependent upon the design of the plant, from a grounded output or loop closure contact arrangement.