A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Jack - Connecting device having springs which make electrical contact with mating contacts of a plug.
Jumper - Aka Cross connect.
Key Service Unit (KSU) - Main part of a key telephone system, containing the electronics controlling which line is directed to which phone; mounted in a closet or near the telephone company demarcation point.
Key System - Telecommunications system with multibutton telephone sets on which more than one outside line terminates, allowing several people to answer or use more than one line.
Key Telephone System - see Key System
Kilobit (Kb) - 1000 bits; a data transmission speed measure, not to be confused with KB.
Kilobits per Second (Kbps) - Refers to how fast data is transmitted on a communications path.
Kilobyte (KB) - A measure of computer memory.
Kilohertz (Kz) - 1000 Hertz, meaning 1000 cycles per second.
Land Line - A normal, regular POTS switched phone line over twisted copper pair.
Latency - Time interval between when a network station seeks access to a transmission channel and access is granted or received.
Leased Line - Any communication channel leased from in interexchange carrier for exclusive use by the lessee. Synonym: private line.
Leased Space Agreement (LSA) - Aka co-location or co-lo. An agreement where communications service vendors or companies use an area of a central office or node for placement of their network interface equipment - agreement is with telecommunications companies.
Least Cost Routing - Where PBX systems are programmed to associate a dialed area code with a specific trunk, which would be the least cost route for that area code.
Line Loop Back (LLB) - For testing transmission lines, where the receive pair of a circuit is connected back into the transmitter; if it receives its own signal without errors, then the line is fine.
Line of Sight - Aka eyeball shot. For terrestrial microwave links; where two radio transceivers with dish antennas point directly to each other, capable of carrying a multitude of different bandwidths depending on size of the dish/antenna, weather, and power emitted - up to about 50 miles between dishes.
Line Protocol - Rules and processes that communications use for transmitting data. Examples are ISDN, Ethernet, token ring, DS1, ATM, frame relay, SONET.
Line Voltage - Refers to voltage on a pair. T1 voltage is -135 volts, POTS is -52 volts.
Link State Advertisement - broadcast packet used by routers in a link-state network routing environment, where packets provide address info to neighboring routers about paths and costs; the resource in link-state routing protocols that collects information used to build and maintain routing tables.
Load Balancing - Where a PBX or central office switch has been designed to allow each network group to share traffic / communication paths.
Local Area Network (LAN) - A number of computers connected together within a building, either via a Ethernet (star or bus), or Token Ring protocol. Most detailed of computer networks, due to applications and operating systems of computers needing to be able to interact with each other. Additionally, LANs usually connect individual computers to a server, which can either run programs, or store data - or both.
Local Access and Transport Area (LATA) - (1) Geographical area designated by the FCC for the provision and administration of telephone service to individual customers. (2) Designated exchanges grouped to serve common social and economic communities of interest.
Local Area Data Transport (LADT) - (1) Method of sending and receiving digital data over existing wires between customer premises and a local carrier. (2) Dial-up LADT lets customers use their lines for occasional data services. (3) Direct LADT transmits simultaneous voice and data traffic on the same lines.
Local Central Office (LSO) - Aka Local Service Office. Performs switching for a specific number-plan area, defined by the first three digits of a seven digit phone number.
Local Exchange - The serving area of a central office. See Local Central Office.
Local Exchange Carrier (LEC) - (1) Provider of local telephone service. (2) Provider of service within a LATA.
Local Loop - (1) Communications lines/services between the telephone subscriber and the LEC switching center. (2) Local connection between the end user and Class 5 central office or end office.
Local Management Interface (LMI) - Software enhancements to frame relay specifications, providing the ability to integrate with a keep alive mechanism (verifying that DLCI's work), multicast mechanism (gives the network server its DLCI), Multicast DLCI, global addressing, and status mechanism. SMI data rids within the customer data pirt of the frame rela frame. More advanced LMI applications are called CLLM - which adds the ability to report congestion control for individual DLCI's.
Logical Channel - Multiplexed channel or frame relay/frame switched media, where no physical wire/fiber/radio/coax path exists, but with in a protocol stack a communications path exists.
Logical Link Control - Sub layer of an OSI data link layer. Handles error control, framing, flow control, and addressing for the lower half of the data link layer MAC addressing; most common form is IEEE 802.2.
Long Distance - Telephone call or communications service that starts in one local service area/area code, and ends in another area code.
Loop - See Local Loop.
Loop Back - See Line Loop Back.
Loop Start Line - From the central office, the type of line that determines the type of signaling required for the line to work. If shared among many devices connected by a PBX or key system, the line is called a trunk.
Loop Start Trunk - Aka POTS and Plain Service Line. Trunk is a line from a central office; two wire central office trunk or dial tone line that recognizes an "off hook" situation when a telephone switch hook puts a 1000-ohm short across the tip, and ring when the handset is lifted - the most common type of phone line.