Label
Label, in telecommunication, is one type of information contained in a signaling message that is used to identify the particular circuit, call, or management transaction to which the message is related.

LAMA: Local Automatic Message Accounting
Local Automatic Message Accounting (LAMA) refers to a set of automatic message accounting equipment and automatic number identification equipment in the central office of local telephone company used for the billing of local phone calls.

LAPB: Link Access Procedure, Balanced
Link Access Procedure, Balanced (LAPB) is a data link layer protocol used to manage communication and packet framing between data terminal equipment (DTE) and the data circuit-terminating equipment (DCE) devices in the X.25 protocol stack. LAPB, a bit-oriented protocol derived from HDLC, is actually the HDLC in BAC (Balanced Asynchronous Class) mode. LAPB makes sure that frames are error free and properly sequenced.

LAP-D: Link Access Procedure, D-Channel
Link Access Procedure, D-Channel (LAP-D), a Layer 2 protocol in the ISDN suite, is used to do call setup and other signaling over the D Channel. Data transmissions take place on B channels. LAP-D is almost identical to the X.25 LAP-B protocol. LAPD is defined in the ITU Q.921 protocol.

LAPF: Link Access Procedure for Frame Mode Services
Link Access Procedure for Frame Mode Services (LAPF), as defined in ITU Q.922, is an enhanced LAPD (Q.921) with congestion control capabilities for Frame Mode Services in the Frame Relay network. LADF is used in the Frame Relay network for end-to-end signaling. LAPF conveys data link service data units between DL-service users in the User Plane for frame mode bearer services across the ISDN user-network interface on B-, D- or H-channels.

LAP-H: Link Access Procedure for H-Channel
Link Access Procedure for H-Channel (LAP-H) performs the same function as B-Channel (LAPB) but operates at rates exceeding DS-0 (64 Kbps). The H-Channel is good for fast facsimile, video, high-speed data, high-quality audio, and multiple info streams at lower data rates.

LAP-M: Link Access Procedure for Modems
Link Access Procedure for Modems (LAP-M) is the data link protocol used by V.32 error-correcting modems. When two LAPM modems establish a session, they transmit data in frames using bit-oriented synchronous techniques. An attached computer still sends data to the LAPM modems as standard asynchronous input, but the modem transmits it as frames.

LAPS: Link Access Procedure-SDH
Link Access Procedure - SDH (LAPS), a variant of the original LAP protocol, is an encapsulation scheme for Ethernet over SONET/SDH. LAPS includes data link service and protocol specification used in transporting IP packets over SDH networks. LAPS provides a point-to-point unacknowledged connectionless service over SONET/SDH. LAPS enables the encapsulation of IPv6, IPv4, PPP, and other higher-layer protocols. X.86 Defines Ethernet over LAPS.

LASS Code: Local Area Signaling Services Code
Local Area Signaling Services (LASS) Codes are numbers that customers enter on their telephone tough-pad to access special features of the telephone system. The most well-known LASS codes are *67 to toggle Caller-ID blocking and *69, for Last Call Return.

LASS: Local Area Signaling Service
Local Area Signaling Service (LASS) is a group features provided by virtually all switches of central offices that uses existing customer lines to provide some extra features to the end user or business user. Those features are based on delivery of calling party number via the local signaling network. Local CCS7 (Common Channel Signaling Seven) is required for all configurations. Typical features of LASS are (1) Automatic Callback, (2) Automatic Recall, (3) Customer-Originated Trace.

Last Choice Route
Last Choice Route refers to the routing algorithm that is the last-choice group trunk group (or a series of last-choice trunk groups) between two switching systems.

Last Mile
Last Mile, also known as the first mile, refers to the final phase or construction to deliver or complete connectivity from a communications provider to an end customer. The last mile communications providers are usually the telecommunications and cable television service providers. "Last mile" is typically seen as an expensive challenge because that "fanning out" all the wires and cables is a considerable physical undertaking.

Last Mile Technology
Last-mile technology refers to the telecommunications technologies that provide connection services to and from the home or business. The typical last-mile technologies include xDSL, Cable and cable modem access (DOCSIS), wireless access (802.16), and optic fiber and its transmission technologies.

LATA: Local Access And Transport Area
Local Access And Transport Area (LATA) refers to the areas within which the Bell Operating and independent telephone companies can provide telephony services. Inter-LATA connections must be provided by Interexchange or long-distance carriers. This was created by the 1984 divestiture and defines a geographic area in which a local exchange carrier, or LEC provides services or connectivity. Traffic that crosses from one LATA to another is the exclusive domain of the IXC. The 358 LATA covers the Chicago area from roughly the Wisconsin state line to just South of Kankakee, and just West of Aurora and Ottawa to Lake Michigan and the Indiana state line.

LCV: Line Code Violation
Line Code Violation (LCV) is an error event in the occurrence of either a Bipolar Violation (BPV) or Excessive Zeroes (EXZ) Error Event on a DS1/T1 interface.

LDN: Listed Directory Number
Listed Directory Number (LDN) is an organization's main telephone number that appears in the telephone book.

Leased Line
Leased Line is a permanent telephone connection between two points set up by a telecommunications common carrier. Typically, leased lines are used by businesses to connect geographically distant offices. Unlike normal dial-up connections, a leased line is always active. The fee for the connection is a fixed monthly rate. The primary factors affecting the monthly fee are distance between end points and the speed of the circuit. Because the connection doesn't carry anybody else's communications, the carrier can assure a given level of quality. For example, a T-1 channel is a type of leased line that provides a maximum transmission speed of 1.544 Mbps. You can divide the connection into different lines for data and voice communication or use the channel for one high speed data circuit. Dividing the connection is called multiplexing. Increasingly, leased lines are being used by companies, and even individuals, for Internet access because they afford faster data transfer rates and are cost-effective if the Internet is used heavily.

LEC Billing
LEC Billing is arrangement whereby the LEC (Local Exchange Carrier) invoices the customer for some of all telecommunications services.

LEC Card
LEC Card (Local Exchange Carrier Card) is the billing arrangement which enables the caller to bill calls to an authorized calling card issued by a LEC (Local Exchange Carrier)

LEC Charges
LEC Charges refers to charges that are the responsibility of the LEC (Local Exchange Carrier).

LEC: Local Exchange Carrier
Local Exchange Carrier (LEC) is, as its name reveals, a telephone company providing local telephone service.

LERG: Local Exchange Routing Guide
Local Exchange Routing Guide (LERG) refers to a documents end of offices and their relationship to Tandem Offices produced by Bellcore Traffic Routing Admin (TRA)

LH: Line Hunting
Line Hunting (LH) is a feature in telephony, also called multi-line hunting, that allows multiple telephone lines going into a business or promises to all act as a single group, called a hunting group (or multi-line hunting group). If the line called is busy, the call will be forwarded to the next available line. Only if all the lines in the group are busy, the calling party will get a busy signal.

Line Busy Tone
The Line Busy Tone indicates that the called customer's line has been reached but that it is busy or being rung or on permanent signal. When a line busy signal is applied by an operator, it is sometimes called a busy-back tone. Line Busy Tone is Low Tone on and off every 0.5 seconds.

Line Code
Line Code refers to a code in telecommunication that is chosen for use within a communications system for transmission purposes. A line code will typically reflect technical requirements of the transmission medium, such as optical fiber or shielded twisted pair. These requirements are unique for each medium, because each one has different behaviors related to interference, distortion, capacitance and loss of amplitude.

Line Equipment
Line Equipment refers to the telephony equipment located in a central office and associated with a particular line. This includes a line relay or equivalent that is activated when the customer's telephone is off-hook.

Line Finder
Line Finder is a component of a switch which locates an idle line and connects it to the line requesting service.

Line Link
Line Link refers to the input side of the switching network in the Number 5 Crossbar system.

Line Load Control
Line Load Control refers to a control process that limits the number of customers who can obtain dial tone in telephony system.

Line Noise
Line Noise refers to a noise originated in a transmission path of telephony system.

Line Number
Line Number refers the 4-digit XXXX number assigned to a North American telephone within a NXX exchange.

Line Relay
Line Relay refers to relay equipment associated with a customer's line that is used to alter the switching of a demand for service for that line. It can also be used to deny incoming access to a line already in use.

Line Segment
Line Segment is the expanse of fiber-optic cable(s) between 2 network locations.

Line Signaling
Line Signaling is a signaling method for transmitting signaling traffic between equipment to terminate and continuously monitor part or all of the traffic circuit. For example, supervisory signaling between exchanges provides the busy, idle, or out-or-service status of circuits.

Line Speed
Line Speed is the maximum rate of transmission at which signals may be transmitted over a given channel. It is usually measured in Baud or Bits per second.

Line Turnaround
Line Turnaround is the time required to change data transmission direction on a telephone line.

Linear Distortion
Linear Distortion refers to, in the telecommunications system, the undesirable changes in the amplitude of a transmitted signal due to imperfections in the transmission path.

Link-by-Link Signaling
Link-by-link Signaling is a signaling scheme, in which signaling messages are transmitted "one link at a time" in a multi-link connection. The network performs processing at each intermediate switching point for subsequent transmission. In the SS7 system, Link-by-link Signaling is the procedure used to exchange signaling messages between two Signaling Points (SPs) that are either directly connected to each other, or are connected via STPs (Signaling Transfer Point).

LLU: Local Loop Unbundling
Local Loop Unbundling (LLU) is the process used in telecommunication to allow operators to use the twisted pair telephone connections from the central offices of telephone exchange to the customer premises. This local loop is owned by the incumbent local exchange carrier.

LNP: Local Number Portability
Local Number Portability(LNP) refers to the feature that was defined in the Telecommunications Act of 1996 as the "ability of users of telecommunications services to retain, at the same location, existing telecommunications numbers without impairment of quality, reliability, or convenience when switching from one telecommunications carrier to another." The Telecommunications Act mandates that all telecommunications service providers (wireline and wireless) provide, to the extent technically feasible, number portability in accordance with the requirements prescribed by the Commission.

Load
Load refers to, in telecommunications system, a volume of traffic that equals the sum of the holding times for a number of calls or attempts. Loads are normally measured in CCS or ERLANGS. A statement of load is inherently an average of all of the instantaneous loads over a basic time interval such as an hour.

Load Balancing
Load Balancing generally refers to distributing processing and communications activity evenly across a computer network so that no single device is overwhelmed. In routing, it means the ability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Load balancing increases the utilization of computers and network bandwidth. In Web services, load balancing scheme is also applied by employing two or more Web servers. If one server starts to get swamped, requests are forwarded to another server with more capacity.

Load Coil
Load Coil is an inductance coil installed at regular distances along a telecommunications transmission line to improve the transmission characteristics of the line over the range of voice frequencies. It's also called Loading Coil.

Loaded Lines
Loaded Lines is a transmission line that has had load coils installed in series with each conductor, usually at definite spaced intervals. A common plan used in the U.S. is 88 millihenry coils installed at 6000 foot intervals.

Local Access Mileage
Local Access Mileage refers to a recurring charge rate element for dedicated (non-switched) private lines that are based on mileage to the Central Office.

Local Channel
Local Channel is: (1) in LEC (Local Exchange Carrier) tariff, the local loop that connects customer premises to serving LEC wire centers. (2) in tariff, the network components (transmission, switching, etc.) used to connect customer premises to serving IXC POPs (Point Of Presence).

Local Exchange Loop
Local Exchange Loop refers to the interconnection between customer premises equipment and telephone central office

Local Loop
Local Loop is the line from the premises of a telephone subscriber to the telephone company CO.

Long-Haul Communications
Long-haul communications refer to the following meanings: (1) Pertaining to circuits that span large distance, such as the circuits in interLATA, interstate, and international communications. (2) communications among users on a national or worldwide basis in the military community. Compared to tactical communication, Long-haul communications are characterized by higher levels of users, such as the National Command Authority, or more stringent performance requirements, such as higher quality circuits. etc.

Longitudinal Voltage
Longitudinal voltage refers to a voltage in telecommunications system induced by or appearing along the length of a transmission medium.

Loop
Loop, in telecommunications, is a pair of phone numbers, usually consecutive, like 836-9998 and 836-9999. They are used by the phone company for testing.

Loop Length
Loop Length is a complete electrical circuit. In telecommunication, it typically refers to the pair of wires that winds its way from the central office to the telephone set or system at the customer's premises.

Loop Start Signaling
Loop Start Signaling, also known as loop signaling or loop start, is a method of signaling in telephony where a DC closure is applied to a phone line (loop), and the start of DC current flow indicates a change from on-hook to off-hook.

Loop Transmission Facilities
Loop Transmission Facilities refer to telephony equipment that connects switching systems to customer premises equipment throughout the serving area.

Loop-Start Trunk
Loop-start Trunk, also called POTS line and plain-service line, is a two-wire central-office trunk or dial-tone line that recognizes off-hook status when a telephone switch hook puts a 1000-ohm short across the tip and ring as the handset is lifted.

Low Tone
Low Tone is a generic tone used with various interruption patterns for the specific tones. Low Tone is 4800 Hz and 620 Hz at -24 dBm0/frequency. On some systems manufactured before 1974, Low Tone was 600 Hz modulated at 120, 133, 140 or 160 Hz at 61-71 dBmc. The following are a list of specific Low Tones: Line Bust Tone, Reorder, Reverting Tone, No Circuit Tone, No Such Number, Vacant Code, Group Busy Tone, Deposit Coin Tone, Dial Off-Normal Tone, Trouble Tone, Dial Jack Tone, Dial Test Signal, Class of Service.

Low-Density Parity-Check Code
Low-density parity-check code is an error correcting code used in a method of transmitting information over a noisy transmission path. Low density parity check (LDPC) codes were introduced along with an iterative probability-based decoding algorithm by Gallager in the early 1960's. These codes were constructed using sparse random parity check matrices and showed promising distance properties. However, they went largely unnoticed until the advent of turbo codes, where they were “rediscovered” by MacKay, who showed that they perform almost as close to capacity as turbo codes. More recently, Richardson and Urbanke have developed irregular LDPC codes that perform even better than turbo codes for very large block lengths (n>10^5) and can come within 0.1 dB of the Shannon capacity.

LPC: Linear Predictive Coding
Linear Predictive Coding (LPC) is a speech encoding scheme that uses periodic pulses to excite a filter, similar to the way human voice is produced. The code is predictive in that it uses knowledge of past data (represented as vectors) to predict future values in a feed forward manner. It is a speech analysis technique as well as a method for encoding good quality speech at a low bit rate. It provides accurate estimates of speech parameters, and is relatively efficient for computation.

LPF: Low-Pass Filter
Low-pass Filter (LPF) is a filter that low frequencies can be tranmited well and frequencies higher than the cutoff frequency is attenuated or reduced. It's sometimes called a high-cut filter for that reason.

LRC: Longitudinal Redundancy Check
Longitudinal Redundancy Check (LRC) is an error checking method that generates a parity bit from a specified string of bits on a longitudinal track. In a row and column format, such as on magnetic tape, LRC is often used with VRC, which creates a parity bit for each character.

LSRR: Loose Source and Record Route
Loose Source and Record Route (LSRR) is an option that provides a means for the source of an internet datagram to supply routing information to be used by the gateway in forwarding the datagram to the destination, and to record the route information.

LSSU: Link Status Signal Unit
Link Status Signal Unit (LSSU) is an SS7 message that carries one or two octets (8-bit bytes) of link status information between signalling points at either end of a link. It is used to control link alignment and to provide the status of a signalling point (such as a local processor outage) to the remote signalling point.

LT: LATA Tandem
LATA Tandem (LT) is a BOC (Bell-operating Company) switching system that provides an intraLATA traffic concentration/distribution point for EO (End Office) switching systems or other tandems within a LATA.

LTB: Last Trunk Busy
Last Trunk Busy (LTB) refers to a measurement of the number of times the last trunk in a trunk group was busy during measurement period.

LTCCS: Last Trunk CCS
Last Trunk CCS (LTCCS) refers to the load in CCS carried on the last trunk in a high usage trunk group.

LTE: Line Terminating Equipment
Line Terminating Equipment (LTE) refers to a device in a telecommunication network system that originate and /or terminate line signals. LTEs can originate, access, modify, or terminate the transport overhead, or can perform any combination of these actions.