Locked Mode-LZW

Locked Mode

In SONET networks, a mode of operation for a Virtual Tributary (VT) group. A VT group can function in either locked or floating mode. While floating mode minimizes delays in distributed VT switching, locked mode is used to enhance the efficiency of the network devices performing the switching.

Locked Resources

An Intel Plug and Play term . Resources that must be used by the same card each time the system is booted . The configuration manager cannot assign these resources to any other card.

Locked Virtual Tributary Mode

The timing of the virtual tributary is locked (in frequency and phase) to the timing of the STS-1. While offering easy visibility and access to DS0 bytes, it adds extra delay, and buffering and reformatting complexity. Intended for switch-to-switch transmission where both are already synchronized. Not expected to have much usage.


Telco-speak for a storage area, often an urban storefront, where phone company installers and repairman can pick up and drop off tools and installation material such as phones, wire and hardware. These places are prime targets for burglary and robbery, and often have no identification to show their valuable contents.


Preventing several people getting to and changing the same data in a shared database simultaneously . Locks may be permanent and prevent access completely, or they may be "advisory." A user is warned the data is being used by someone else and that the data is not presently available. Locks prevent the destruction of data that can occur if two people access a file at the same time. In any data base or other computer system, there are typically two types of "locks" ” record and file locks. A record lock occurs when an airline agent pulls up your travel plans. No other travel agent can access those records at that time. A file lock occurs when the whole file is locked up. This might occur in a centralized word processing program. The whole document will be locked when it is being used by someone.


A PBX feature. Denies the attendant the ability to re-enter an incoming central office connection directly terminated or held on her position, unless specifically recalled by the phone user.


A company goes public, i.e. does an IPO ” Initial Public Offering. Its stock is listed on the stock exchange and starts trading hands. Shares owned by insiders (management, directors, etc.) cannot be sold because they are subject to a "lock up." This is a time period that has been negotiated with them by the underwriter as part of his commitment to take the company public. Under the agreement they cannot sell their shares in a company for (typically) six to 12 months right after the initial public offering.


It has been documented that locusts have formed swarms measuring up to one mile wide, 100 feet deep, and 50 miles long. They may travel more than 2,000 miles. A swarm this enormous has been known to contain as many as 40 billion locusts.


In Buenos Aires, they have places (normally privately owned) where there are a lot of telephone booths, fax machines, that you walk in, make a call, pay and walk out. The word in Spanish in Buenos Aires is "locutorio," which was the name given to a place in convents or prisons where nuns or prisoners could speak to visitors from behind bars (in both cases). The word comes from Latin and is mostly used in Spain (Telefonica de Espana purchase part of the old Argentine telco). This definition contributed by Jorge E. Corbalan, head translator in the Arthur Andersen office in Buenos Aires.


Letter of Disconnect (you don't pay,.. you don't play).


A magnetic ore of iron, used in the making of early compasses.


Loss of Frame. LOF is a generic term with specific variations of meaning, depending on the signal standards domain in which it is being used. In the OSI/ATM world for instance, LOF is a condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost frame delineation. This is used to monitor the performance of the PHY layer. In the SONET world also, LOF is a condition detected in the signal overhead at the receiver, indicating that a valid framing pattern could not be obtained. There is however no "LOF indication" per se transmitted in the SONET overhead: SONET uses the AIS-L overhead indication to inform downstream equipment that the receiving equipment upstream has experienced a failure. A hierarchy of LOF defect and alarm notifications is implemented at the LOF-detecting equipment based on the duration the condition persists. See also AIS and SEF.


See Logarithm.


Log. A mathematical function. The exponent that indicates the power to which a number is raised to produce a given number. For example, the equivalent of 100 to base 10 is 2. In other words, 10 squared = 100.

Log In

The process of identifying and authenticating oneself to a computer system. Used to control access to computer systems. See Login Script.

Log File

Also spelled logfile, which is very efficient in terms of keystrokes but which is very poor spelling. A log file is simply a file that tracks access activity for a host resource. For instance, a log file might contain information relative to those who access your Web site. Such information might identify user name, user domain, the length of time spent on each page, and which links they exercise. See also Log In and Log Off.

Log Off

  1. To type in the needed keystrokes for ending a session that's on-line with a computer. Often those keystrokes are "Logoff." Usually it's very easy to Log Off. It's more difficult to Log On.

  2. Employees wear their photo-ID badges in little plastic holders attached by a clip to their clothing. It's a good idea to "log off" when you're in public. This means to turn your badge around so nobody can see whom you work for.

Log On

To enter the needed keystrokes to start an on-line session with a computer. "Logging On" may be done with a computer that's local or one that's long distance and your work is done over communications lines.

According to the Vermonter's Guide to Computer Lingo, log on is making the wood stove hotter.


See Log File.


Logic is the application of mathematical analysis and deductive reasoning to propositions that may or may not be true or false. The logic we're interested in owes much to the work of George Boole in the mid-19th century. He formulated a system that could be applied to the relationships between propositions to which only a binary choice of truth existed, i.e. yes or no. The first application of the Boolean Algebra that derived from this was Shannon's research into the analysis of relay switching circuits in 1938. Logic is not common sense. See common sense.

Logic Bomb

Program routine that destroys data. For example, a logic bomb may reformat the hard disk or insert random bits into data files. It may be brought into a personal computer by downloading a corrupt public domain program. Once executed, it does its damage right away and then stops, whereas a virus keeps on destroying. Another definition of a logic bomb is that it is a resident computer program that lies dormant for a period, and then triggers an unauthorized act when a certain event, such as a date, occurs.


In networking, logical means the way it works, the way the software sees it. In contrast, physical means how it's physically connected, which is often very different. For example, A physical addresses is translated from a logical address. Allow me to illustrate . When someone dials your telephone number, they are dialing a logical address; in other words, the series of numbers means nothing until they are translated into a physical address. The physical address is the port to which your local loop is connected to which your telephone is connected. Similarly, your postal address is a logical address. It has meaning only when translated by the post office into the plot of earth on which your house sits. A logical address, on the other hand and just to confuse you, may have no fixed physical address. For example, your e-mail address has no fixed physical address. Rather, it is translated into an IP (Internet Protocol) address which is associated with your e-mail server, which can be moved from place to place. Ultimately, your e-mail address actually is associated with you, and you and your computer can move all over the world without losing access to your e-mail. Rather, you gain access to your e-mail by going on a network connected to the Internet ” e.g. dialing a telephone number (logical address) which connects you to your e-mail server which has a physical address which can change as the server is moved from one location to another.

Logical Address

See Physical Address.

Logical Block Address

A logical block address is a sequential address for accessing blocks on storage media. The first block of the media is addressed as block O and succeeding blocks are numbered sequentially until the last block is encountered . This is the traditional method for accessing peripherals on a SCSI bus.

Logical Layer

The CVNS layer used to define the virtual networks and provision the services within the physical layer. There are two components that make up the logical layer: Data Access Points (DAPs), and Service Control Manager (SCM).

Logical Terminal Group

LTGRP. An ISDN term for a group of logical terminals connected to an ISDN switch, each of which terminals has a unique Logical Terminal Identifier (LTID). The LTID comprises the LTGRP, which is followed by the Logical Terminal Number (LTNUM).

Logical Terminal Identifier

LTID. An ISDN term. See Logical Terminal Group.

Logical Terminal Number

LTNUM. An ISDN term. See Logical Terminal Group.

Logical Topology

The logical layout of a network, as opposed to the Physical Topology. In the LAN world, for instance, a 10Base-T network is a Star from the standpoint of Physical Topology (the way it looks). Yet the network operates as a logical Bus. In other words, the devices arrayed around the 10Base-T hub connect through ports into the hub chassis which houses a collapsed bus which supports communications over the shared physical path just as does a traditional Ethernet bus network, which is a bus in both physical and logical terms.

Logical Bus

A LAN topology, such as Ethernet, which shares a common communications channel.

Logical Channel

A software based connection through which data is sent. The channel is assigned by the switch. In X.25 talk, a logical channel refers to a virtual connection operated over a physical connection that can support one or more virtual connections simultaneously.

Logical Channel Number

Virtual circuit identified at the packet level of X.25. See Logical Channel.

Logical Client

Refers to one component in a pair of communicating components which is obtaining access to CTI functionality through the other component. This term is used to differentiate between two components which are communicating across an inter- component boundary. See Logical Server.

Logical Drive

A disk drive recognized by the operating system. A computer's logical drives may differ from its physical drives. For example, a single hard disk drive may be partitioned into two or more logical drives. Before MS-DOS 5.0, the biggest logical "drive" that DOS could address was 32 megabytes. If you had a larger hard disk, you partitioned the bigger driver into logical drives of 32 megabytes.

Logical Formatting

The third step in structuring a data medium so that data may be written to it. Logical formatting must follow physical formatting (also called low-level formatting) and partitioning (figuring into how many drives you wanted to slice the one drive into).

Logical Group Node

An ATM term. 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 ID

An AT&T Merlin term. A numbering sequence used to identify station and trunk locations on the communications system control unit.

Logical Layer

The CVNS layer used to define the virtual networks and provision the services within the physical layer. There are two components that make up the logical layer: Data Access Points (DAPs), and Service Control Manager (SCM).

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 Link Control

LLC; A protocol developed by the IEEE 802 committee, common to all of its LAN standards, for data link-level 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.

Logical Modem Interfaces

LMIs are to Microsoft's MAPI what SPIs are to TAPI. LMIs serve network-based fax servers and multi-port fax boards . MAPI sits on top of Microsoft's Exchange and other MAPI-compliant messaging systems.

Logical Node

An abstract representation of a peer group or a switching system as a single point.

Logical Node ID

A string of bits that unambiguously identifies a logical node within a routing domain.

Logical Port

Lport. The logical interface between an endpoint(i.e., end process or program) and a communications or transmission facility. Multiple logical ports can be associated with a single physical port that connects to a transmission circuit that is capable of being fractionalized, or channelized. For example, a T-1 circuit commonly is channelized into 24 voice-grade channels, each of which is, in effect, a separate logical circuit contained within a single physical circuit. Each channel is associated with a single logical port that terminates the transmission is a given set of logic and, ultimately, in a single terminal device. A T-3 circuit typically comprises 28 T-1s, each of which is a logical circuit (typically comprises 24 logical circuits of its own) that terminates in a logical port. Logical ports also are used to terminate Frame Relay VCs (Virtual Circuits). See also Port.

Logical Provisioning

An AT&T term for the establishment of network services by changing software controls, rather than by physically installing or rearranging hardware.

Logical Ring

A network which is treated logically as a ring even though it maybe cabled as a physical star topology.

Logical Server

Refers to one component in a pair of communicating components which is providing CTI functionality to the other component. This term is used to differentiate between two components which are communicating across an inter-component boundary. See Logical Client.

Logical Unit Interface

See LU 6.2.


French for software.


The process whereby a user gains access to a computer or network.

Login Script

When users log into a local area network, they may wish to do many things or the network supervisor may wish them to do several things. These commands are part of something called a "login script." In computerize (Novell's words), a login script contains commands that initialize environmental variables , map network drives, and/or control the user's program execution. Login scripts are similar to batch files. The familiar AUTOEXEC.BAT can be thought of as an MS-DOS login script.

Login String

A means of gaining access to the network. The string typically consists of three fields: username, destination, and password. The destination and password are optional depending on the network configuration.


The process whereby a user exits a computer or network.


Line Overhead. 18 octets in a SONET frame for purposes of controlling the reliable transport of payload data between SONET network elements such as repeaters. LOH and SOH comprise Transport Overhead (TOH).


Letter of Intent. You sell stuff. You want to sell your stuff to someone. But that someone won't give you a legally-binding Purchase Order. But you need something to show your bank in order to convince them to give you some money. So you ask your customer to give you a "Letter of Intent" which says they'll buy whatever the Letter says they'll buy, perhaps. IN short, a Letter of Intent means nothing, except that your "customer" loves you enough to write a letter on his letterhead. And the Letter is worth the paper it's written on ” however you can use it to convince your banker to give you a loan.


Local Off Network Access Line. Similar to Foreign Exchange Service, this line terminates local calls from an end user's private network.

Long Distance

Any telephone call to a location outside the local service area. Also called toll call or trunk call.

Long Haul Communications

That type of phone call which reaches outside a local exchange or serving area.

Long Haul Data

Special conditioning of the inter-office channel in order to meet performance specifications needed for processing data over the circuit. The long haul circuit will have the same type of conditioning as the local loop at each end.

Long Haul Modem

A modem or other communications device that can transmit information over long distances.

Long Key

A long key is a character held down for a prescribed period of time. The time period is generally longer than the time for other keys. In call reorigination, the # sound is defined as a "long key." This definition was kindly provided by Karen Shelton, Systems Engineer, IEX Corporation, Richardson, TX.

Long Lines

AT&T Long Lines. The department of AT&T which operates long distance toll service. It is no longer called Long Lines. It is called AT&T Communications.

Long Reach

Long reach refers to optical sections of approximately 25 kilometers or more in length and is applicable to all SONET rates. See Long Reach Ethernet.

Long Reach Ethernet

LRE. Long-Reach Ethernet is a proprietary Cisco extension to the IEEE 802.3 Ethernet LAN (Local Area Network) standard. LRE extends fully symmetric, full-duplex Ethernet connectivity at speeds of 5-15 million bits per second (Mbps) over distances of up to 5,000 (1,524 meters) feet over unconditioned Cat 1/2/3 (Category 1, 2 or 3) UTP (Unshielded Twisted Pair). While the exact transmission rate supported depends on the type and quality of the UTP, the exact distances, and numerous other factors, the most optimistic specifications are speeds of 5 Mbps over distances up to 5,000 feet, 10 Mbps up to 4,000 feet and 15 Mbps up to 3,500 feet. Note: Traditional Ethernet runs at 10 Mbps (also at 100 Mbps and 1 Gbps), over distances of up to 100 meters over Cat 3 (or better) UTP. Frequency Division Duplex (FDD) allows LRE transmissions to coexist with POTS (Plain Old Telephone Service), PBX, or ISDN signaling services over the same pairs. LRE also can be provisioned in the same bundle (i.e., binder group) as ADSL (Asymmetric Digital Subscriber Line). LRE makes use of Quadrature Amplitude Modulation (QAM), a modulation technique that uses shifts in both signal amplitude and phase to define each symbol. The system administrator or telecom manager may choose profiles that use different modulation options (QAM-256, QAM-128, QAM-64, QAM-32, QAM-16, QAM-8, and QAM-4) and frequency plans according to the line specification and rate definition. LRE is designed for application in hotels, office buildings , and other multi- tenant and multi- dwelling units with old POTS inside wire and cable systems that can't be upgraded easily, if at all. LRE provides an ISP with the ability to take high-speed DSL to the premises, connect to a whole bunch of Cisco gear (i.e., splitters, switches, servers, and the like) and software, and provide high-speed Internet access over old, beat-up telephone wire. It's a great idea. See also ADSL, Ethernet, FDD, and QAM.

Long Tones

First, we invented touchtone, also called DTMF, Dual Tone Multi Frequency tones. You'd punch your number with tones, instead of dialing them. Then someone thought you could control telephone response gadgets, like voice mail, interactive voice response, etc. with touch tones. For these gadgets to work, they had to "hear" the tones you sent. No one really set standards as to the minimum length tone they would hear. But it was generally conceded that they were to be 120 milliseconds . So some manufacturers of telephone equipment started to make phone equipment that, if you pushed a touchtone button, the machine would only sent a touchtone of 120 millisecond duration. That was called a short tone. It wasn't very useful because the manufacturers quickly discovered that many pieces of equipment couldn't respond that quickly. And the manufacturers got complains that their customers couldn't call their voice mail, their bank, etc. As a result, some manufacturers of equipment brought out new hardware (replacing the old) to allow you to send "long tones," which are now defined as touchtones that last for as long as you hold down the button ” just as it is (and has always been) on a normal single line, non-electronic, non-digital telephone. Isn't progress wonderful? See also DTMF for a much longer explanation of tone dialing.

Long Wavelength

Light whose wavelength is greater than about 1 micrometer.

Long Wavelength Band .

The optical band, or window, specified by the ITU-T at a wavelength range between 1565nm and 1625nm (nanometers) for fiber optic transmission systems. See also C-Band, E-Band, O-Band, S-Band, and U-Band.

Longest Available

This is a method of distributing incoming calls to a bunch of people. This method selects an agent based on the amount of time that each agent has been on the phone. This allows for an equitable distribution of calls to each agent. See also Top Down and Round Robin.

Longest Prefix Matching

Longest prefix matching is an address searching method in CIDR (Classless Interdomain routing), where a group of hosts whose addresses have a common prefix are grouped as a subnet. This common prefix is the network address of this subnet. To find out whether a host belongs to a particular subnet, a router simply masks off the lowest x number of bits in the address. Conversely, to route a packet the router simply compare the destination address with the address of all the subnets and find the subnet whose naddress has the best (longest) match. This look-up is most efficiently done with tenary CAMs. For detailed discussion, see page 164-165 in High-Performance Communication Networks by J. Walrand and P. Varaiya.

Longevity Testing

When you're building a computer telephony system, many problems do not come to light until it's been running under high traffic for a long term. According to Steve Gladstone, author of the book "Testing Computer Telephony Systems," (available from 212-691-8215), there can be slow memory leaks, counter overflows, or disk fragmentation which slows down data access, system resets that cause calls to be dropped inadvertently, and so on. Frequently these issues are discovered only after thousands of calls are placed or after some random call pattern has occurred. Longevity tests, according to Gladstone, provide a high load to a system over an extended period of time. The most effective way to do this is to run a load test based on your busy hour usage profile over several days and track failures over the entire testing period. If failure rates increase, or specific failures occur, the events leading up to the fault can be relatively easily duplicated . If the system generating the load provides good error tracking and event logging, it may be possible to immediately identify the sequence that caused the fault, the corresponding reactions of the computer telephony system, and even immediately duplicate the fault causing scenario.


Longhorn is the next major release of today's 32-bit Windows operating system. Long horn will have both 32-bit and 64-bit versions.


The distance in degrees from one Meridian to any other. Longitude is usually measured from the prime meridian (Greenwich, England).

Longitudinal Balance

A measure of the electrical balance between the two conductors (tip and ring) of a telephone circuit; specifically, the difference between the tip-to- ground and ring-to-ground AC signal voltages, expressed in decibels.

Longitudinal Conversion Loss

LCL. A measure (in dB) of the differential voltage induced on a conductor pair as a result of subjecting that pair to longitudinal voltage. LCL is considered to be a measure of circuit balance.

Longitudinal Mode

An optical waveguide mode with boundary condition determined along the length of the optical cavity .

Longitudinal Redundancy Check

LRC. An error checking technique based on an accumulated collection of transmitted characters . An LRC character is accumulated at both the sending and receiving stations during the transmission of a block of data. This accumulation is called the Block Check Character (BCC) and is transmitted in the last character in the block. The transmitted BCC is compared with the accumulated BCC character at the receiving station for an equal condition. When they're equal, you know your transmission of that block has been fine. LRC commonly is used in combination with VRC (Vertical Redundancy Checking) to improve the reliability or error control in asynchronous transmission and in support of the ASCII coding scheme.

With VRC, a check bit, or parity bit added to each ASCII character in a message such that the number of bits in each character, including the parity bit, is odd (odd parity), or even (even parity). The term comes from the fact that the bits representing each character of data logically is viewed in a vertical fashion. When LRC is used in combination with VRC, the parity of a block (set) of data characters is checked for parity longitudinally (along the horizontal plane) of characters, as though they were laid out logically in a matrix format. For instance, the word "CONTEXT" consists of 7 letters , each of which consists of 7 bits, viewed in a block matrix format as follows :





1 1 0 0 1 0 0 0


1 1 1 0 0 0 0 0


0 1 1 1 1 0 1 0


0 1 1 0 0 1 0 0


0 0 0 1 0 1 1 0


0 0 0 0 0 0 0 1


1 1 1 1 1 1 1 0


0 0 1 0 0 0 0



The transmitting machine sums the bit values for each character, beginning with "nothing," which is an even value in mathematical terms. In the case of the letter "C," for instance, the next bit is a "1" bit, which creates an odd value. The next bit is a "1" bit, which creates an even value. The next four bits are "0" bits, which do not change the even value. The seventh bit is a "1" bit, which creates an odd value, once again. Assuming that the device is set for odd parity, which is the default, it will insert a "0" bit in the eighth bit position, retaining the odd value. (Should the device be set for even parity, a "1" bit would have been inserted in the eighth bit position.) Should the value of the 7 information bits be an even value, the device appends a "1" bit in order to create an odd value. Across the longitudinal plane, the transmitting device accomplishes exactly the same process, appending "0" to retain odd values or "1" bits in order to create odd values.

After the data, character-by-character, has been formatted in this fashion, each bit sequence is transmitted across the network to the target device, which also is set for odd (or even) parity. The receiving device goes through exactly the same process, examining each character for parity. If the parity does not match the expectation of the receiving device, the subject character is flagged as errored, although no remedial action is taken. As VRC exposes the transmission to reasonable likelihood that two bits in a given character can be errored in the process of transmission of each character, that the parity of the character therefore would not be affected, and that the receiving device would not detect the fact that the character was errored, this technique is known as "send and pray." LRC substantially improves the likelihood that errors in a block of data will be detected, although there remains potential for compensating errors to affect the data, without detection. Any remedial action must be accomplished on a man-to-machine basis. See also Vertical Redundancy Checking and Parity.

Longitudinal Transmission Check

LTC. An even or odd parity check at fixed intervals during data transmission.

Longitudinal Wrap

A tape applied longitudinally with the axis of the core being covered, a opposed to a helical, or spiral, tape wrapped core .

Look Ahead Routing

A Common Channel Signaling System 7 (SS7) technique that determines the availability of a communications channel before the call is sent over the network. The technique maximizes efficiency and use of the public switched network. See Signaling System 7.

Look-Up Table

  1. A translation table. You dial a certain number. But the number is meaningless. For the phone system to complete the call, it needs routing instructions. It gets that by "looking up" that number in a table, which translates that number to another number that is now meaningful to the switching network. There are lots of applications for Look-up Tables. Least Cost Routing tables are essentially look up tables. IN-WATS dialing works by looking up the 800 number and finding its real ten digit normal number. Most private networks use look up tables to translate the number dialed by the internal user into a number that the network can recognize.

  2. A set of addresses (source and destination) used by a bridge or router to determine what should be done with a packet. As the packet comes in, its address information is read and compared with the information in the look-up table. Depending on the information, the bridge may forward the packet, or discard it, leaving it for the local LAN. Many bridges and routers can build their look-up tables as they operate . See also 800 Service, Eighthundred Service, Bridge, Personal 800 Number and Router.


A real-time Internet collaboration freeware tool that gives the user the ability to view another user's screen that is equipped with the program. It can be used to edit material, review graphics or provide immediate training and support.

Loomed Speed-Wrap

See Bundled Cable.


  1. Typically a complete electrical circuit.

  2. The loop is the pair of wires that winds its way from the phone company's central office to the telephone set or system at the customer's office, home or factory, i.e. "premises" in telephones.

  3. In computer software. A loop repeats a series of instructions many times until some prestated event has happened or until some test has been passed. An infinite loop (i.e., a loop that never stops) causes a computer to crash. See also Crash.

Loop Antenna

An antenna consisting of one or more complete turns of wire, both ends of which are to be connected to the input circuit of the radio receiver.

Loop Back

A diagnostic test in which a signal is transmitted across a medium while the sending device waits for its return. See Loopback and Loopback Test.

Loop Bonding

Loop bonding is also sometimes referred to as "inverse multiplexing" and is conceptually the same as what is called "trunking" in Ethernet parlance. It refers to combining several parallel data paths so that they appear as one logical bigger transmision channel capable of handling more bandwidth than just a single path. The specifics of how this all work depend on each vendor's implementation.

Loop Checking

A method of checking the accuracy of transmission of data in which the received data are returned to the sending end for comparison with the original data.

Loop Circuit

Generally refers to the circuit connecting the subscriber's set with the local switching equipment.

Loop Current Detection

When a modem, telephone or fax card (etc.) seizes the line (i.e. completes the connection between tip and ring terminals of the telephone cable) current flows from the positive battery supply in the telephone central office, through the twisted pair in the loop, through the card (or phone) and back to the central office negative terminal where it is detected, showing that this telephone or telephone device is off hook. The fax card or modem can detect problems such as disconnects, shutting down the connection or a busy signal.

Loop Emulation Service

See LES.

Loop Extender

Device in the central office that supplies augmented voltage out to subscribers who are at considerable distances. It provides satisfactory signaling and speech for such subscribers.

Loop Plant

Telco-talk for all the wires and hardware and poles and manholes used to connect their central offices to their customers.

Loop Qualification

Test done by the phone company to make sure the customer is within the maximum distance of 18,000 feet from the central office that services that customer. 18,000 is the maximum distance an ISDN-BRI phone line will work.

Loop Reverse-battery

A method of signaling over interoffice trunks in which changes associated with battery reversal are used for supervisory states. This technique provides 2-way signaling on 2-wire trunks; however, a trunk can be seized at only one end. It cannot be seized at the office at which battery is applied. It is also called reverse-battery signaling.

Loop Signaling

A method of signaling over circuit paths that uses the metallic loop formed by the line or trunk conductors and terminating circuits.

Loop Signaling Systems

Any of three types of signaling which transmit signaling information over the metallic loop formed by the trunk conductors and the terminating equipment bridges.

Loop Start

LS. You "start" (seize) a phone line or trunk by giving it a supervisory signal. That signal is typically taking your phone off hook. There are two ways you can do that ” ground start or loop start. With loop start, you seize a line by bridging through a resistance the tip and ring (both wires) of your telephone line. The Loop Start trunk is the most common type of trunk found in residential installations. The ring lead is connected to -48V and the tip lead is connected to OV (ground). To initiate a call, you form a "loop" ring through the telephone to the tip. Your central office rings a telephone by sending an AC voltage to the ringer within the telephone. When the telephone goes off-hook, the DC loop is formed. The central office detects the loop and the fact that it is drawing DC current and stops sending the ringing voltage. In ground start trunks, ground Starting is a handshaking routine that is performed by the central office and the PBX prior to making a phone call. The central office and the PBX agree to dedicate a path so incoming and outgoing calls cannot conflict, so "glare" cannot occur. See GLARE. Here are two questions that help in understanding:

How does a PBX check to see if a CO Ground Start trunk has been dedicated? To see if the trunk has been dedicated, the PBX checks to see if the TIP lead is grounded. An undedicated Ground Start Trunk has an open relay between OV (ground) and the TIP lead connected to the PBX. If the trunk has been dedicated the CO will close the relay and ground the TIP lead.

How does a PBX indicate to the CO that it requires the trunk?

A CO ground start trunk is called by the PBX CO Caller circuit. This circuit briefly grounds the ring lead causing DC current to flow. The CO detects the current flow and interprets it as a request for service from the PBX.

See also POTS.

Loop Test

A way of testing a circuit to find a fault in it by completing a loop and sending a signal around that loop. See Loopback.

Loop Through

A type of phone system wiring that allows phones to connect to one cable in parallel going to the common central switching equipment. The most common type of Loop Through wiring is that which you have in your home. You have one cable with two conductors ” a red and a green ” winding through your home. Whenever you want to connect a phone, you simply attach it to the red and green conductors. The other way of connecting phones is called HOME RUN. In that system, every phone has its own one, two or three pairs of conductors which wind their lonely way back to the central PBX or key system cabinet. In Loop Through wiring, many phones share one set of cables. In Home Run Cabling, only one phone sits on that line.

Loop Timing

A way of synchronizing a circuit that works by taking a synchronizing clock signal from incoming digital pulses .

Loop Up/Loop Down

In T-1, there are generally two loopback types, LLB (line loopback) and TLB or DLB (terminal or DTE loopback). Loop Up refers to activating one of these loop backs, where as Loop Down refers to deactivating one of these loopbacks.


The output of a "loop through."


The output input of a "loop through."


Type of diagnostic test in which the transmitted signal is returned to the sending device after passing through a data communications link or network. This allows a technician (or built-in diagnostic circuit) to compare the returned signal with the transmitted signal and get some sense of what's wrong. Loopbacks are often done by excluding one piece of equipment after another. This allows you to figure out logically what's wrong. (It's called Sherlock Holmes deductive reasoning.) See Loopback Test.

Loopback Test

A test typically run on a four-wire circuit. You take the two transmit leads and join them to the two receive leads. Then you put a signal around the loop and see what happens. Measuring differences between the sent and the received signal is the essence of a loopback test. See Loopback.


Problem encountered in distributed datagram routing in which packets return to a previously visited node.

Looping Plug

A device used to provide a physical loop on a T-1 or 56/64K DDS circuit. The plug is inserted into the demarcation jack and allows LECs (local exchange carriers) and CLECs (competitive local exchange carriers ) to test circuits for continuity. A T-1 looping plug is pinned 1-4, 2-5 using a RJ-45 plug. A 56/64K DDS looping plug is pinned 1-7, 2-8 using an RJ-45 plug.

Loopstart Circuit

The standard world-wide telephone circuit. For the phone to signal the phone system that it wants to make a call, it applies a DC termination across the phone line. See Loop Start for a longer explanation.

Loose Tube Buffer

A cable construction in which the optical fiber is placed in a plastic tube having an inner diameter much larger than the fiber itself. The loose tube isolates the fiber from the exterior mechanical forces acting on the cable. The space between the tube and the fiber is often filled with a gel to cushion the fiber.

Loosely Coupled

A computer system architecture consisting of multiple computer systems, each with its own dedicated memory and its own copy of the operating system, connected over a communications link. See also Tightly Coupled.


Loss of Pointer. LOP is a generic term with specific variations of meaning, depending on the signal standards domain in which it is being used. In the OSI/ATM world for instance, LOP is a condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost the pointer to the start of cell in the payload. This is used to monitor the performance of the PHY layer. In the SONET world also, LOP is a condition detected in the signal overhead at the receiver, indicating that a payload position pointer could not be obtained. There is however no "LOP indication" per se transmitted in the SONET overhead: SONET uses the AIS-L overhead indication to inform downstream equipment that the receiving equipment upstream has experienced a failure. A hierarchy of LOP defect and alarm notifications is implemented at the LOP-detecting equipment based on the duration the condition persists. See also AIS.


LOng Range Aid to Navigation. A radio-navigation system which helps you find where you are. It works by timing the difference in reception of pulses from one or more fixed transmitters, usually on land. It's a radio based systems that's pretty good for coastal waters where there are LORAN transmitters. The maximum range is about 1,400 miles at night (about a half that during the day), in virtually any sort of weather. LORAN doesn't cover much of the rest of the earth and its accuracy varies depending on electronic interference and geographic variations. The first LORAN transmitters were put into operation by the U.S. Navy in 1944. LORAN range limitations were overcome in 1973, when the U.S. Navy first installed the "Transit" SatNav (Satellite Navigation) system, which set the stage for a much better system known as GPS (Global Positioning Satellite System). Over time and as costs have decreased, even small pleasure craft have replaced their LORAN receivers with GPS. See also GPS.

Lord of The Rings

While known as a painter, sculptor, architect, and engineer, Leonard da Vinci was the first to record that the number of rings in the cross section of a tree trunk revealed its age. He also discovered that the width between the rings indicated the annual moisture.


Microsoft jargon for large size organizations. They are Microsoft's main customers.


  1. Loss of Signal. LOS is a generic term with specific variations of meaning, depending on the signal standards domain in which it is being used. In the OSI/ATM world for instance, LOS is a condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost the received signal. This is used to monitor the performance of the PHY layer. In the SONET world also, LOS is a condition directly detected at the physical level (photonic or electronic) at the receiver. There is however no "LOS indication" per se transmitted in the SONET overhead: SONET uses the AISL overhead indication to inform downstream equipment that the receiving equipment upstream has experienced a failure. A hierarchy of LOS defect and alarm notifications is implemented at the LOS-detecting equipment based on the duration the condition persists. See also AIS.

  2. Line of Sight. Another silly acronym is NLOS, which stands, predictably, for Non Line of Sight.


The drop in signal level between two points on a network. It is important to distinguish between "loss" and "level". Level is the amplitude, or signal strength, and is measured at finite points known as Transmission Level Points (TLPs). Loss is the difference between levels over a circuit, between two TLPs, and is measured in decibels (dB). Loss occurs constantly throughout telephony ” from long distance circuits to switches, as switches set up connections via internal circuits. Loss is cumulative. Add two circuits each with a loss of 10 dB. You will have 20 dB loss in the total circuit. The human ear can detect a 3 dB loss.In figuring losses on fiber optic cables, you add up the individual losses from the connectors, the splices and the cable itself.

Loss Budget

A loss budget is the maximum amount of signal degradation a data communications network can withstand before it becomes susceptible to errors and/or loss of data. The idea is a establish a "loss budget" by consulting your equipment vendors for recommended wire types and maximum allocable lengths of cable before you build the network. We first heard the idea of a loss budget from The Siemon Company, Watertown CT.

Loss Deviation

Denotes the variation of the actual loss from the designed value.

Loss of Cell Delineation

LCD. An ATM term. Cell Delineation is accomplished at the Transmission Convergence (TC) sublayer of the ATM Physical Layer (PHY), working in tight formation with the Physical Medium (PM) sublayer. It is at the TC sublayer that the responsibility is assumed for Physical Layer operations that are not medium independent. For example, it is at this sublayer that the ATM cell switch interfaces with a SONET transmission system. Cell Delineation is responsible for defining the cell boundaries at the originating endpoint (e.g., ATM cell switch or ATM workstation) in order that the receiving endpoint can reassemble (i.e., identify and recover) all cells associated with a data payload that has been segmented (i.e., cut up into ATM cells ). Cell Delineation is achieved by the receiving endpoint's locking onto the 5-octet cell headers. A failure in this process is known as Loss of Cell Delineation (LCD).

Loss of Frame

See LOF.

Loss of Pointer

See LOP.

Lossless Compression

Image- and data-compression applications and algorithms, such as Huffman Encoding, that reduce the number of bits a file would normally take up without losing any data. In this way, no information is lost or altered in the compression and/or transmission process. Lossless compression is particularly important for alphanumeric text files, as the integrity of the data is affected dramatically if even one bit is lost. PKZip and WinZip are examples of products that use lossless compression techniques. See also Lossy Compression.

Lossy Compression

Compression techniques that result in the some loss of data are known as lossy. While the data file is not completely accurate, once compressed and decompressed, the savings in storage memory and transmission bandwidth/time are considerable. Audio, video and image files often are compressed via a lossy technique, as the savings in storage and transmission bandwidth are so significant, while the level of loss is often not noticeable. JPEG, MPEG and Wavelet are all examples of lossy compression techniques. See also JPEG, Lossless Compression, MPEG, and Wavelet.

Lost Call Attempt

A call attempt that cannot be further advanced to its destination due to an equipment shortage or failure in the network.

Lost Calls Cleared

Traffic engineering assumption used in Erlang C that calls not satisfied on the first attempt are held (delayed) in the system until satisfied.

Lost Calls Held

Traffic engineering assumption used in Poisson that calls not satisfied on the first attempt are held in the phone system for a period not exceeding the average holding time of all calls.

Lost Wages

An endearing term for a town called Las Vegas whose claim to fame is gambling. Hence the term "lost wages."


A method, authorized by the Congress, designed to provide the FCC with an alternative or option to comparative hearings for allocating spectrum space to competing applicants in various services.

Lotus Express

An e-mail communications software program for PC users of MCI Mail that allows the user to automatically send and receive messages, as well as binary files, such as spreadsheets or documents.


See Sound.

Loudspeaker Paging Access

Interface to customer-provided paging equipment.


Zero scores in tennis are called "love." In France, where tennis first became popular, a big, round zero on scoreboard looked like an egg and was called "l'oeuf," which is French for "egg". When tennis was introduced in the US, Americans pronounced it "love." I can continue further with bad yokes...


Graphics service bureau slang for a file that an art director obsessively wants to output in every possible variation. "Yeah, I know we're ripping it to the Iris proofer for the ninth time. This one's a lovejob." Definition courtesy Wireless Magazine.

Lovelace, Ada Augusta

Ada Augusta Lovelace was the daughter of Lord Byron, the English poet. Miss Lovelace is regarded as the first computer programmer because she worked for the computer pioneer Charles Babbage. A computer language was named after her. That language is called ADA.

Low Battery Cutoff

An uninterruptible power supply (UPS) definition. This UPS feature automatically switches off battery power before the batteries discharge beyond safe limits. Without this feature, batteries can be taken into deep discharge , making them useless.

Low Entry Networking

LEN. A peer-oriented extension to SNA, first implemented on IBM's System/36, that allows networks to be more easily built and managed by such techniques as topology database exchange and dynamic route selection.

Low Frequency

The band of frequencies between 30 and 300 kilohertz.

Low Frequency RFID Tags

They typically operate at 125 KHz. The main disadvantages of low frequency tags are they have to be read from three feet closer and the rate of data transfer is slow. But they are less expensive and less subject to interference than high frequency tags.

Low Level Combining

A process frequently used in multichannel transmitters for combining channels or carriers at some processing stage prior to the transmitter output.

Low Level Diplexing

A processing of combining two radio frequency carriers (usually audio and video) at some processing stage prior to the final transmitter output.

Low Level Formatting

The first step in preparing a drive to store information after physical installation in complete. The process sets up the "handshake" between the drive and the controller. Most drivers are now low level formatted at the factory. See Physical Formatting.

Low Level Language

A programming language that uses symbols ” one step away from the machine language of a computer. Low level computer languages, such as Assembler and C, actually manipulate the bits in computer registers. Higher level languages such as Basic and Fortran will take care of the piddling details of doing specific functions when you give it a broad command like "PRINT". In a lower level language, you must provide all the details of instruction necessary in the code (program) to perform the operation. It is possible to do this by calling standard routines, but still takes up the programmers' time in deciding which routines, and keeping the registers straight as he designs the program.

Low Noise Amplifier

LNA. Typically a parametric amplifier in a satellite earth station.

Low Noise Converter

LNC. A pre-amplification device consisting of a low noise amplifier and down converter built into one unit.

Low Order Bit

Least Significant Bit (LSB). See also High-Order Bit, and Least Significant Bit.

Low Pass Filter

A device that cuts frequencies off above a certain point and allow all other frequencies to pass. Opposite of high pass.

Low Power FM Radio Station


Low Power Television Service

LPTV. A broadcast service that permits program origination or subscription service or both via low powered television translators. LPTV operates secondarily to regular television stations. Transmitter output is limited to a 1000 watts for a UHF station, 10 watts for a VHF station, except when VHF operation is on an allocated channel when 100 watts may be used.

Low Speed Loopback

A closed circuit feature useful for maintenance or testing.

Low Speed Signal

Signal traveling at the DS1 rate of 1,544 Mb/s or at the DS1C rate of 3,152 Mb/s.

Low Tier

See High Tier.

Low Voltage

A low voltage condition exist when fewer than 105 volts AC is present at a 120 VAC outlet or HOT conductor. This figure was chosen by many manufacturers of electronic and telephone equipment. It is also the test of "low voltage" tested by a wonderful AC electric outlet-testing product called the Accu-Test II made by Ecos Electronics Corporations of Oak Park, Illinois. Below 105 volts, motors deteriorate and electronic circuits overheat. Long-term damage can occur to most gadgets plugged into an electrical outlet which consistently delivers below 105 volts. Also 105 volts is below the stated tolerance levels of all North American power utilities who state that their acceptable power is 120 volts plus or minus 10 percent. If your power is consistently below 105 volts, you should contact your local power utility.

Low Voltage Differential Signaling

LVDS: Low Voltage Differential Signaling is a new data interface standard that is defined in the TIA/EIA-644 and the IEEE 1596.3 standards. It is essentially a signaling method used for high-speed transmission of binary data over copper . It uses a 350 mV voltage swing between two wires rather than a signal referenced to the ground. This low voltage differential is what delivers high data transmission speeds and inherently greater bandwidth at lower power consumption with low electromagnetic interference (EMI.) The receiver for LVDS utilizes the differential signal to determine the state and rejects the common noise for better noise immunity.

Low Water Peak Fiber

The presence of moisture in optical fibers results in significant levels of attenuation (i.e., power loss) at 1383 nm (nanometers). Depending on the magnitude of that "water peak" loss, wavelengths within +/- 50 nm also can be affected. This water peak is caused by residual moisture deposited during the manufacturing process. Specifically, it largely is caused by hydrogen atoms in the water molecules. The hydrogen atoms readily diffuse through the glass matrix of an optical fiber and are trapped at points of defect in the glass structure. The process of manufacturing low water peak fibers involves reducing water levels in the fiber from 10 ppb ( parts -per-billion) to less than 1 ppb. This is accomplished by exposing the fiber to deuterium gas or deuterium blends under elevated temperature and pressure. The deuterium atoms displace the hydrogen atoms at the defect sites, which lowers the water peak and increases the capacity of the fibers by supporting a wider range of spectrum. See also Rain Attenuation.

Lower Case

Upper- and lower-case letters are named "upper" and "lower," because in the time when printers set pages using loose type, the " upper-case " letters were stored in the case on top of the case that stored the smaller, " lower-case " letters.

Loyalty Management

Verizon Wireless has a department called "Loyalty Management." Their main job is handling cancellations from customers.

Loyalty Market

Giving awards to customers for shopping with you. The airlines have the best loyalty program around ” frequent flyer miles.


Linear Power Ampflier.


  1. Linear Predictive Coding. Low bit rate voice (LBRV) digitizing technique that requires a bandwidth of only 2.4 or 4.8 Kbps. This technique may result in poor quality voice signals.

  2. Late Payment Charge.


Line Printer Daemon, a process on Berkeley spooler implementations that provides LPR systems.


IBM's protocol under NetView for monitoring of dial-up modems for error correction.


Low Pass Filter: In an MPEG-2 clock recovery circuit, it is a technique for smoothing or averaging changes to the system clock.


On January 20, 2000, the FCC adopted rules creating a new, low power non-commercial FM radio (LPFM). A normal FM station transmits at thousands of watts of power. This level of power means that the station will need lots of expensive transmitting equipment. costing at least a million dollars. But for that money it will be able to cover an entire urban area. The LPFM station is designed to let individuals and small organizations own and operate radio stations for a wide variety of not-for-profit reasons and transmit only to small groups of people within limited geography. In this sense, the FCC is trying to bring station creation closer to normal people ” in the same way that anyone can create a web site. A LPFM station is a 10 or 100 watt transmitter. This level of power gives the station a range of up to 3.5 miles. A transmitter this size and its antenna might cost $2,000 to $5,000. In a city, the range of an LPFM transmitter could cover a small neighborhood. The owner-operators of low power FM radio stations could include religious groups, churches , colleges, PTA-sponsored school stations, foreign language stations, race track pit and parking areas and be an extension to a school or college public address system.


Lines Per Inch. The number of lines both horizontal and vertical, that a facsimile machine will print in a square inch.


  1. IntraLATA Primary Interexchange Carrier. A Primary Interexchange Carrier for IntraLATA long distance traffic, the LPIC may be different than the PIC (Primary Interexchange Carrier). While the PIC typically is your carrier for all long distance, it may be designated only for InterLATA traffic if you also have designated a LPIC. Traffic to both the LPIC and PIC is automatically routed from a given location when dialing 1+ in equal access areas. The LPIC is identified by a LPIC Code (LPIC Code) and the PIC by a PIC Code (PICC) which is assigned by the local telephone company to the telephone numbers of all the subscribers to those carriers to ensure the calls are routed over the correct network. When a subscriber switches long distance carriers, it often is referred to as a PIC change.

  2. Local Presubscribed Interexchange Carrier.


Lines Per Minute. A reference to printer speeds.


See Logical Port.


Link Peripheral Processor or Link Peripheral Processing.


The LPR command is used to queue print jobs on Berkeley queuing systems.


  1. Line Profile System.

  2. Lightning Protection Subsystem.


Line Protection Switch.

LPT Port

A logical designation for a series of I/O (Input/Output) addresses that allows the computer to communicate with a parallel printer.


The first or primary parallel printer port on the IBM PC or clone. LPT2 is the second parallel port. COM1 is the first serial port. LPT1 is usually the default printer port, i.e. the one your computer will print to, if you don't tell it something else.


Low Power Television Service. A broadcast service that permits program origination or subscription service or both via low powered television translators. LPTV operates secondarily to regular television stations. Transmitter output is limited to a 1000 watts for a UHF station, 10 watts for a VHF station, except when VHF operation is on an allocated channel when 100 watts may be used.


Link Quality Analysis. See Automatic Link Establishment.


  1. Longitudinal Redundancy Check. A system of error control based on transmission of a block check character based on preset rules. The check character formation rule is applied in the same manner to each character on a bit by bit basis. See Longitudinal Reduancy Check.

  2. Loop Resiliency Circuit. Hub circuitry that allows devices to be inserted into or removed from an active FC-AL (Fibre Channel Arbitrated Loop) loop.


  1. Line Regenerating Equipment.

  2. Lightwave Repeating Equipment.

  3. Long Reach Ethernet. See Long Reach Ethernet.


Low Rate Encoding-Digital Speech Interpolation.


Long Run Incremental Cost.


Local Routing Number. A 10-digit telephone number. The term is used in the context of LNP (Local Number Portability). See LNP.


Long Range Radar.


Least Recently Used. Refers to an algorithm that sorts items according to time last accessed and then discards the oldest items in the list to free up needed space.

LS Trunk

Loop-Start Trunk. A trunk on which a closure between the tip and ring leads is used to originate or answer a call. High-voltage 20-Hz AC ringing from the telephone company signals an incoming call. See LOOP START.


Single Mode, Single-Fiber Interconnection Cable. An AT&T definition.


Link State Advertisements: OSPF link state information comprised of four variables: Router Link Advertisements, Network Link Advertisements, Summary Link Advertisements and Autonomous System (AS) Link Advertisements. All but the AS Link Advertisements are flooded through a single OSPF area only. The AS Link advertisement s are flooded throughout the entire OSPF network.


An ATM term. Link Service Access Point: Logical address of boundary between layer 3 and LLC sublayer 2.


Line Side Answer Supervision.


Least Significant Bit and Least Significant Byte. That portion of a number, address or field which occurs right most when its value is written as a single number in conventional hexadecimal or binary notation. The portion of the number having the least weight in a mathematical calculation using the value.


Lightguide Stranded-Cable Interconnect Equipment.


Lightguide Stranded-Cable Interconnect Module.


Lightguide Stranded-Cable Interconnect Terminal.


Link layer Service Data Unit.


Local Support Element.


Large Scale Integration. Refers to micro electronic components which combine many hundreds of transistors on an integrated circuit. See CHIP.


Link Support Layer. A layer within the Novell Open Data-Link Driver specification. This layer lets multiple protocol stacks access a network card simultaneously.


Local Service Management System. The database from which each LEC gets updates from the NPAC for portability requests . See NPAC.


Local Service Office. Defined for North America as a six digit number consisting of the area code and the first three digits of the exchange code (i.e. 410-638 (area code for northern Maryland, with exchange code for Belair Maryland). Used to identify a geographical area and local service provider for that circuit. An LSO is important when ordering circuits from a telephone company, especially a long distance one.


Local Service Order Administration system. An OSS (Operations Support System) used by LECs (Local Exchange Carriers) to administer service orders such as orders for new service, service rearrangements, and changes of carrier. See also LNP, NPAC and OSS.


See Local Service Ordering Guidelines.


Local Service Order Record.


  1. Local Service Provider. Another term for a Local Exchange Carrier (LEC).

  2. Label Switched Path. See MPLS (Multiprotocol Label Switching).

  3. Local Service Provider. See Location tracking.


  1. An ATM term. Leaf Setup Request: A setup message type used when a leaf node requests connection to existing point-to-multipoint connection or requests creation of a new multipoint connection.

  2. Line Service Request. Document in the LEC (local exchange carrier) world which is used for porting requests, directory listing changes, trunk ordering etc. It has lots of slots for hand written letters, and uses lots of trees (often a full sheet for each number regardless of the volume of the request) also available in proprietary electronic systems from larger LECs, such as US West, Southwestern Bell and GTE.

  3. Local Service Request. A term that was spawned by the Telecommunications Act of 1996, which formalized competition in the local exchange domain. A LSR is a form, or series of forms, used by the CLEC (Competitive Local Exchange Carrier) to request "local service" from the ILEC (Incumbent LEC). Specifically, the LSR is used by the CLEC to request a local loop from the ILEC, meaning that the CLEC wants the ILEC to provide a local loop from the customer's premises to the CLEC's termination equipment, which typically is housed in the ILEC's (CO) Central Office. A LSR also is used to request that the ILEC port the subscriber's telephone number to the CLEC. In full form, porting the telephone number means that the subscriber's telephone number remains the same ” it's just ported to the CLEC through full Local Number Portability (LNP). If the CLEC and/or the ILEC do not have the necessary software in place to accomplish such a level of number portability, the subscriber may wind up with two telephone numbers ” one number is the new CLEC number, and the other is the old ILEC telephone number. Effectively, in this latter scenario, incoming calls are forwarded to the new number in an arrangement known as Interim Number Portability (INP). The LSR may be in either paper or electronic form, and contains all information required for administrative, billing, and contact details. See also CLEC, ILEC, INP, and LNP.

  4. Label Switch Router See Label Switch Router and MPLS (MultiProtocol Label Switching).


LATA Switching System Generic Requirements.


Line Supervisory Equipment.


  1. Line Terminator.

  2. Logical Terminal.

  3. An ATM term. Lower Tester: The representation in ISO/IEC 9646 of the means of providing, during test execution, indirect control and observation of the lower service boundary of the IUT using the underlying service provider.


Last Trunk Busy.


Line Trunk Controller.


ISDN Line Trunk Controller.


Logical Terminal Class classifies each ISDN terminal based upon the type of messaging that is exchanged between the terminal and circuit switch part of the ISDN switch. There are 3 classes: BRAKS, BRAMFT, and BRAFS. The newer (BCS-31 and above) ISDN sets should be defined with BRAMFT or BRAFS. The decision to use BRAMFT or BRAFS depends on what kind of service is being provided, for example, MADN groups should be defined on a BRAFS terminal. See also LTID.


A satellite term. Longitudinal/Linear Time Code.


Label Traffic Control System. LTCS is a prepackaged implementation of the Multiprotocol Label Switching (MPLS) standard from a Boston, U.S.-based company called Harris & Jeffries. www.hjinc.com. According to Interactive Week of May 3, 1999, MPLS has emerged as a compelling technology because it offers service providers a mechanism for controlling the flow of traffic across their networks, which is a crucial requirement for offering advanced applications such as voice services and virtual private networks. In addition, MPLS has been embraced by makers or Asynchronous Transfer Mode gear because it provides a layer of translation between IP and ATM."


Line Terminator Type DP.


SONET Lite Terminating Equipment: ATM equipment terminating a communications facility using a SONET Lite Transmission Convergence (TC) layer. This is usually reserved for end user or LAN equipment. The SONET Lite TC does not implement some of the maintenance functions used in long haul networks such as termination of path, line and section overhead. In short, line terminating equipment includes network elements which originate and/or terminate line (OC-N) signals. LTEs originate, access, modify, and/or terminate the transport overhead.


Logical Terminal Group. See Logical Terminal Group.


Logical Terminal Identifier. LTIDs are required for each logical terminal connected to an ISDN switch. Each LTID allocated must be unique. An LYID consists of a logical terminal group name (LTGRP), followed by a logical terminal number (LTNUM). i.e. ISDN 99 and LCME1 100, where ISDN and LCME1 represent the LTGRP, and 99 and 100 represent the LTNUM within the group.


Local Transport Network. A term for fiber ring.


Logical Terminal Number.


See Linear Tape Open Architecture.


  1. Line Test Position.

  2. List Transmission Path.


Line Terminator Type PA.


Line Terminator Type PB.


Local Transport Restructuring. An FCC ordered tariff restructuring by the LECs on access charges for IXCs.


Letters Shift.

  1. Physical shift in a terminal using Baudot Code that enables the printing of alphabetic characters.

  2. Character that causes the shift.


Loop Testing System.


Line Terminator Test Board.


  1. Line Unit.

  2. Logical Unit, access port for users in SNA. In a bisync network, a port through which the user gains access to the network services. A LU can support sessions with the host- based System Services Control Point (SSCP) and other LUs.

  3. Local Use flag. Occasionally used to initialized approval for local cellular calls. The Cellular carrier insures that local users are registered with a local system.

LU 6.2

Logical Unit Interface. Version 6.2. An IBM SNA protocol that allows for peer-to- peer or program-to-program communications. The LU 6.2 protocol standard frees application programs from network specific details. On an IBM PC, a LU 6.2 program accepts commands and passes them on to an SDLC card to communicate directly with the mainframe or a token ring handler. LU 6.2 enables users to develop applications programs for peer-to- peer communications between PC's and IBM host systems. It increases the processing power of the PC user without the constraints of mainframe-based slave devices, i.e. 3274/3276 controllers. It creates a transparent environment for application-to-application communications, regardless of the types of systems used or their relative locations. Also referred to as Advanced Program-to-Program Communication (APPC).

LU Type 1

LU 1 is the SNA protocol that describes generic input/output devices (e.g. line printer).

LU Type 3

LU 3 is the SNA protocol that describes a print output device that uses 3270 data streams.

Lucent Technologies

On September 30, 1996, AT&T spun off AT&T Technologies (previously Western Electric), its manufacturing operations and its Bell Labs into a separate company called Lucent Technologies. Lucent then comprised Bell Laboratories (R&D), Network Systems (development and manufacture of switches, and related systems and software for the carrier market), Business Communications Systems (development, manufacture, marketing and servicing of advanced communications products for business customers), Microelectronics Group (design and manufacture of high-performance integrated circuits, optoelectronic components, and power systems), and Consumer Products (design, manufacture, sales, servicing and leasing of both wired and wireless communications products for consumers and small businesses). One reason for the split was that AT&T Technologies' major customers (the RBOCs) were viewed as unlikely to purchase equipment and services from their strongest likely competitor (i.e. AT&T) in a deregulated and competitive environment. In March 2000, Lucent sold its small and mid- sized business sales group to Expanets, a division of NorthWestern Corporation. In July 2000, Lucent spun off Enterprise Networks Group, as Avaya Communication. Avaya manufactures voice, converged voice and data, customer relationship management, messaging, multi-service, networking, and structured cabling products and services. Lucent Technologies, minus Avaya, designs and delivers the systems, software, silicon and services for network service providers and large enterprises . See also AT&T and Avaya. www.lucent.com.

Ludd, Ned

See Luddites.


The common myth: Luddites were people who hated industrial progress and went around destroying machinery. Wrong: They were people who had no problem with progress. They simply wanted to share in the fruits, i.e. be paid more. In the Sunday New York Times of December 6, 1998, William Safire explains all. Here's an excerpt: In Leicestershire in 1779, a man named Ned Ludd broke into a house, and in what was reported to be 'a fit of insane rage,' destroyed two machines used for knitting hosiery. The breaking of such knitting frames ” machinery invented two centuries before ” had been going on for nearly a century. Ludd, however, did it with such gusto and flair that subsequently, whenever machines of any sort were found smashed, the excuse was given that 'King Ludd must have been here.'

What was Ludd's motive? Was he a lover of hand-knitted hosiery? Did he prefer going barefoot? Or was he making some sort of unadorned social protest of deeper significance? Revisionist historians say that Ludd and other frame-wreckers were protesting poor working conditions and low wages at the beginning of the Industrial Revolution. However, between 1811 and 1816, organized bands of masked men swore allegiance to 'King Ludd' rather than the British sovereign , and waged a war against the serflike conditions spawned by the users of textile machinery. 'If the workmen dislike certain machines,' explained The Nottingham Review in 1811, 'it was because of the use to which they were being put, not because they were machines or because they were new.' That living-condition claim was swept aside by commercial interests and officialdom, which hung the label Luddite on protesters not for demanding a living wage but for obstructing the march of technological progress. The historical revisionists argue that others attributed the anti-machinery 'cause' to the Luddites. Intellectuals and romantics like the poets Blake, Byron, Shelley and Wordsworth picked up that anti-technology theme, but identified with its other side. In the ''dark Satanic mills'' of industry, they saw the human spirit being stifled. Lord Byron wrote an inflammatory 'Song for the Luddites' in 1816. Its first stanza: 'As the Liberty lads o'er the sea/Bought their freedom, and cheaply, with blood,/So we, boys, we/Will die fighting, or live free,/And down with all kings but King Ludd!' Mary Shelley, daughter of the feminist Mary Wollstonecraft and wife of the poet, gave the Luddite theme dramatic power in her 1818 novel , 'Frankenstein.' The danger of rampant technology is expressed by the monster, who says to Dr. Victor Frankenstein, ''You are my creator, but I am your master.' Between the sweatshop operators and the romantic poets , the meaning of Luddite became fixed as '' radical opponent of technological or scientific progress.'


On TV shows like "Law & Order," cops who want info on the bad guys' phone calls, pull their LUDs. LUDs is an acronym for Local Usage Details ” a record of incoming and outgoing calls for a particular phone number. The cops get this list from the local phone number. These lists are one reason the bad guys like to use coin phones.


Something which sticks out and onto which a wire may be connected by wrapping or soldering.


The brightness signal in a video transmission.


The measurable, luminous intensity of a video signal. Differentiated from brightness in that the latter is nonmeasurable and sensory . The color video picture information contains two components: luminance (brightness and contrast) and chrominance (hue and saturation). The photometric quantity of light radiation. Luminance is that part of the video signal which carries the information on how bright the TV signal is to be.

Luminiferous Ether

Heinrich Rudolf Hertz discovered the phenomenon of the propagation of electromagnetic energy through space. He assumed that there was some conducting matter in the air that supported the arcing of a spark from a positive to a negative terminal. To test the theory, he tried to arc a spark through a vacuum tube, and succeeded. He assumed that the magical conducting matter was so small that it could not be identified and could not be voided from the tube. He named this non-existent matter "luminiferous ether." Bob Metcalfe and his associates later named their magical LAN (Local Area Network) technology Ethernet. See also Edison Effect.


LANE User Network Interface. Pronounced "looney," as in "Sometimes all these acronyms make me looney." An ATM term for standardized network interface protocol between a LANE (Local Area Network Emulation) client and a LANE Server. See also LANE and LNNI.


Logical Unit Numbers. An identification number given to devices connected to a SCSI adapter. Each SCSI ID can have eight LUNs. Normally, there is only one device with LUN 0. See Daisy Chain and SCSI.


A person who " hangs around" online bulletin boards and forums, browsing through the messages and, if moved, replying to some of them. That's one definition. Here's another: A visitor to a newsgroup or online service who only reads other people's posts but never posts his or her own messages, thus remaining anonymous. See Lurking.


The practice of reading an Internet mailing list or Usenet newsgroup without posting anything yourself. Everywhere you look there's a Slim Shady lurking. He could be working at Burger King, spitting on your onion rings. Or so I'm told. In the online world, lurking is not considered particularly antisocial ; in fact, it is a good idea to lurk for a while when you first subscribe so that you can get a feel for the tone of the discussions in the group and come up to speed on recent history. See Lurker.


A talented lady with endless patience. She checked and spell-checked every definition until her eyes fell out of her head. She said, politely, she'd had more exciting jobs. Certainly better paying ones. If you find a mistake in this dictionary, please email Lusha. It's all her fault. LDing@Amherst.edu. When she becomes a world-famous concert pianist, you'll be able to tell all your friends , you knew her when she was a lowly lexicographer.


A contraction of luminance and flux and a basic unit for measuring light intensity. A Lux is approximately 10 foot candles .


A ITU-T X.25 packet switched network operated in Luxembourg by the Luxembourg government.


A SANs definition. Low-Voltage Differential Multipoint (for low-power bus applications requiring multi-point interconnections, where LVDS is not feasible .)


Low Voltage Differential Signaling is a new data interface standard that is defined in the TIA/EIA-644 and the IEEE 1596.3 standards. It is essentially a signaling method used for high-speed transmission of binary data over copper. It uses a 350 mV voltage swing between two wires rather than a signal referenced to the ground. This low voltage differential is what delivers high data transmission speeds and inherently greater bandwidth at lower power consumption with low electromagnetic interference (EMI.) The receiver for LVDS uses the differential signal to determine the state and rejects the common noise for better noise immunity.


Low Voltage TTL.


Telephone Assistance Plan Surcharge.


To walk with a lisp.


A World Wide Web (WWW) browser developed at the University of Kansas for students and faculty who use dumb terminals (e.g., VT100) for connection to mainframe and midrange computers running either the UNIX or the MVS operating system. Lynx was built on an early version of the Common Code Library developed by the CERN WWW project headed by Tim Berners-Lee. Lynx is keyboard-oriented and text-only, rather than being fully featured, graphically-oriented, mouse-driven, audio- and video-capable. Given its origins and orientation (dumb terminals and big computers), that's understandable. In the context of high-performance PCs and Graphical User Interfaces, however, Lynx is not the browser of choice for most of us.


A compression approach falling into the general category of "dictionary methods ," LZ77 was developed in 1977 by Abraham Lempel and Jakob Ziv. LZ77 involves an implicit dictionary in which data is represented by previously processed data. In other words, a given set of data which is exactly the same as a previously transmitted of data need not be restated in full. Rather, a pointer refers to the previous data set. The result is that far fewer bits need be sent to communicate the same information. That yields more efficient use of bandwidth, which always is a limited resource. LZ77 is an asymmetric compression method, as the coding process is relatively time-consuming , while the decoding process is much less so. LZ77 was refined in the LZSS algorithm developed in 1982 by Storer and Szymanski. See also Compression, Dictionary Method, LZSS, LZ78, LZJH, and LZW.


A refinement of the LZ77 compression method. A "dictionary method," LZ78 creates a dictionary of data phrases that occur in the input data. When the compression software encounters an input phrase that previously has been entered into the dictionary, the output is in the much-abbreviated form of the index number of that phrase. The result is that far fewer bits need be sent to communicate the same information. That yields more efficient use of bandwidth, which always is a limited resource. LZ78 was further refined in the LZW algorithm developed by Terry Welch in 1984. See also Dictionary Method, LZSS, LZ77, LZJH, and LZW.


Lempel-Ziv-Jeff.Heath. A compression algorithm developed by Jeff Heath of Hughes Network Systems for use over satellite links, LZJH is based on earlier work by Abraham Lempel and Jakob Ziv.. LZJH is the basis for the V.44 compression standard finalized on June 30, 2000 by the ITU-T. V.44, which supplants the earlier V.42bis modem compression technology, provides 6:1 (i.e., 6 to 1) compression performance. V.44 is intended for use in V.92 modems, the successor to V.90 modems. In combination with V.92 modems, V.44 will have a significant effect on the speed of data transmission, as did the earlier move from V.34 to V.90 modems. See also LZ77, LZ78, V.42bis, V.44, V.90, and V.92.


Lempel-Ziv-Stac. A data compression algorithm developed by Stac Electronics and sometimes used by routers. LZS is based on the LZ77 algorithm developed by Abraham Lempel and Jakob Ziv in 1977. See also LZ77.


Lempel-Ziv-Storer-Szymanski. A data compression method developed in 1982 by Storer and Szymanski, and based on earlier work by Abraham Lempel and Jakob Ziv. LZSS offers a better compression ratio than LZ77, and the decoding process is simpler and faster. Popular archivers such as PKZip make use of LZSS.


Lempel-Ziv-Welsh. A data compression method developed in 1984 by Terry Welch, based on LZ78 by Abraham Lempel and Jakob Ziv. LZW was developed for hardware implementation in high-performance disk controllers. For example, Nortel uses LZW in its Distributed Processing Peripheral (DPP), which is the Automatic Message Accounting Transmitter (AMAT) for the DMS-100 family of central office switches. Nortel selected this non-proprietary protocol and helped promote it as an industry standard. The nominal compression ration is 2.8:1, without considering field suppression. Transmitting data compressed at a ratio of 2.8:1 at 9600 bps is equivalent to transmitting non-compressed data at 27 Kbps. Compatible compression collectors can poll the DPP in compressed or non-com- pressed mode. DPPs equipped with the Data Compression feature can transmit in either compressed or non-compressed mode, based on the collector's polling request for a specific polling session. To preserve data integrity, AMA data are still stored in non-compressed form on the DPP disks. LZW is a lossless data-compression algorithm patented by Unisys. See Lossless, Lossy, and LZ78.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

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