Electronics glossary — Letter L

96 terms starting with L

L1

L1 Frequency – 1575.42 MHz. – one of the two radio frequencies transmitted by the GPS satellites. This frequency carries the Coarse Acquisition Code (C/A code), P-Code, and the nav message.

L2

L2 Frequency – 1227.6 MHz – one of the two radio frequencies transmitted by the GPS satellites. This frequency carries only the P-Code.

L3

Level 3 frequency

L5

Level 5 frequency – 1176.45 MHz – additional frequency used on new ‘Block IIF’ satellites, intended for civilian applications in air traffic control.

LAAS

Local Area Augmentation System

label

An ordered set of characters used to symbolically identify an instruction, a program, a quantity, or a data area. The label also symbolically designates the memory location which is to contain the instruction, etc. The label is, therefore, the symbolic analog of an address. A label may be absolute, relative, direct, or indirect. See also address.

Lacing Cord or Twine

Used for lacing and tying cable forms, hookup wires, cable ends, cable bundles, and wire harness assemblies. Available in various materials and impregnants.

Lambda

The physical distance between two points of identical phase on consecutive cycles of a wave. The symbol for wavelength is lambda, “l”. Wavelength is related to frequency according to the equation l=c/f, where c is the speed of light (3*108 m/s) f is frequency in Hz.

Laminated Cores

Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface which is commonly an oxide finish. Laminated cores are used in some inductor designs but are more common in a wide variety of transformer applications.

laminating

The process of bonding two or more layers of material together, using heat, pressure, and an adhesive.

Laminations

Supplied in stamped letter shapes such as ‘EI’, ‘EL’, ‘EE’, ‘F’, or ‘UI’, they are composed of silicon iron and nickel alloys. Audio and telecommunication transformers use nickel alloys, while silicon iron is generally used for line frequency power transformers.

LAN

Local Area Network – The means by which a local community of users and workgroups can share information and resources electronically. Many communications protocols are used to accomplish this, the most prevalent of which are Ethernet and Token Ring. Usually confined to one building or even one floor. Large companies may have several LANs connected by an internetwork or backbone network.

land

The printed conductive portion of a printed circuit board. See also pad and terminal area.

Lanyard

A device, attached to certain quick-disconnect connectors, that permits uncoupling and separation of connector halves by a pull on a wire or cable.

large-scale computer

A computer that is more sophisticated and faster than a minicomputer; capable of addressing megabytes of memory and of operating several peripherals. A computer suitable for most general-purpose, scientific, and data-processing applications.

large-scale integration

LSI – A term describing the level of complexity or size of an integrated circuit. An LSI circuit is considered to have in excess of 100 digital gates, or equivalent circuitry.

Laser

Light amplification by stimulated emission and radiation. A device that generates or amplifies light by means of a medium that provides optical gain. Common types of lasers include solid state (glass or cystalline bulk material), semiconductor (based on p-n junctions), and gas lasers. Fiber lasers are doped glass lasers designed to amplify the light in optical fibers.

laser diode

A semiconductor device that converts an electrical input into a coherent light output.

Last mile

A reference to the local loop, the distance between a local telco office and the subscriber, a distance actually about 0 to 3 miles (0 to 4 kilometers).

Lateral displacement loss

The loss of power that results from lateral displacement from optimum alignment between two fibers or between a fiber and an active device.

Lay

Refers to direction or sometimes the ratio of lay length to core diameter.

Lay Length

A term used in cable manufacturing to denote the distance of advance of one member, or a group of spirally twisted members in one turn, measured axially. The lay of any helical element of a cable or conductor is the axial length of a turn of the helix of that element.

layout

The topological arrangement of conductors and components in integrated circuit design. A precursor to artwork.

L-Band

The frequency interval from 1 to 2 GHz.

LCD

Liquid crystal display. A seven-segment (typically) display device consisting of a liquid crystal hermetically sealed between two glass plates. The readout is either dark characters on a dull white background or white on a dull black background.

lead frame

A metal frame that includes the leads of a plastic encapsulated DIP. The frame holds the leads in place prior to encapsulation and is cut away after encapsulation.

lead(s)

Generally one or two wires cut to certain length with or without terminals.

leading edge

Refers to a pulse. The leading edge of a pulse is defined as that edge or transition which occurs first. The leading edge is usually the transition from a logic 0 to a logic 1.

Leakage Current

Current flowing from input to output or input to case of an isolated converter at a specified voltage level.

Leakage Inductance

The inductance that does not link the primary in a coil. It is due to the leakage flux.

Leased Line

A transmission line reserved by a communication carrier for the private use of a customer.

LEC

local exchange carrier

LED

Light-emitting diode – A semiconductor diode, generally made from gallium arsenide, that can serve as an infrared or visible light source when voltage is applied continuously or in pulses.

LEO

Low Earth Orbiting (satellites) (See also GEO and MEO)

Levels of packaging

A framework of six categories or levels used to define electrical interconnections by function. Level 1:A level of electrical interconnection that includes all those connections that link an active element to the terminals (leads) of the device. For example, the bond wire linking a semiconductor chip to its lead frame.; Level 2: All those connections linking a circuit board with the components mounted thereon. For example, the connection between the legs of a DIP switch and the circuit board.; Level 3: All those connections linking two or more circuit boards together. For example, the connection between motherboard and daughterboard.; Level 4 :All those connections linking two or more functional subassemblies with the system enclosure. For example, the connection between a power supply and circuit board.; Level 5: All those connections that provide the input/output function of the system. For example, the connection between a circuit board and the connector that provides access to the internal workings of the machine.; Level 6: All those connections linking two or more systems. For example, the interconnection between terminals in a local area network.

LFM

Linear feet per minute, which is a measure of air velocity used to cool a power converter.

Life Cycle

A test to determine the length of time before failure in a controlled, usually accelerated environment.

Life test

Reliability test in which a converter is operated (typically under accelerated conditions) over some period of time in order to approximate its life expectancy.

Lifeline POTS

A minimal telephone service designed to extend a “lifeline” to the telephone system in case of emergency, particularly when electric power is lost.

light-emitting diode

LED – A semiconductor diode, generally made from gallium arsenide, that can serve as an infrared or visible light source when voltage is applied continuously or in pulses.

Limiter

A receiver protector that allows low power signals to propagate from the antenna of a receiver to the next sensitive stage, such as a mixer or LNA, but rejects high power signals that may be incident on the antenna. Limiters are typically self-actuating but may also be controlled by an external bias signal.

Line

Bus used to deliver power to the input terminals of a converter. Also see Bus, High Line and Low Line.

Line Code

Any method of converting digital information to analog form for transmission on a telephone line. 2B1Q, DMT, and CAP are all line codes.

line cord

Standard – A two-wire cord terminating in a two-prong plug at one end.; Grounded – A two-wire-with-ground cord terminating in a three-prong plug.; Both types of line cord are used to connect electrical/electronic equipment or appliances to a power outlet.

Line Effect

Line Regulation.

line impedance

Impedance as measured across the terminals of a transmission line. Frequently, the characteristic impedance of the line.

line printer

A printing device that can simultaneously print several character graphics on hard copy. A line typically consists of 120 characters.

Line Regulation

Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of the regulating device to dissipate unused power. Also see Series Regulator, Shunt Regulator and Post Regulation.

Line transient

Spike or step change in the input to a converter. Input transient protection circuits arc used to shield sensitive components (such as the semiconductor switch) from possible damage due to transients.

Linear

A circuit or component whose transfer function can be accurately described by a first order equation (a straight line, hence the term linear).

linear circuit

A circuit whose output is either an amplified version of its input, or a predetermined variation of its input.

Linear Material

Magnetic material that exhibits fairly constant permeability over a wide range of MMF.

linear polymer

A polymer whose molecules form long chains without cross-linked or branch structures. Usually thermoplastic.

Linear Power Transformer

Transformers that generally operate between 47Hz and 400Hz in power conversion, which alter the input voltage needed for the load. Linear power transformers are very inefficient.

Linear regulation

Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of the regulating device to dissipate unused power. Also see Series Regulator, Shunt Regulator and Post Regulation.

Linearity

For an attenuator, the variation from the best straight line of the attenuation versus control signal transfer function at center frequency, measured in dB or percentage of attenuation. For a VCO, the variation best straight line of the output frequency versus control signal transfer function, measured in per cent. For a system or component: the extent to which the output spectrum is identical to the input spectrum. A system that generates spurious signal is considered to be nonlinear.

Liner

See Core.

link

(1) Physical connection between two nodes in a network. It can consist of a data communication circuit or a direct channel connection. Also an LED signal that indicates connection has been established. (2) A complete network to send and receive data via fiber optics, including transmitter, receiver, fiber, and connectors. (3) The part of the horizontal cabling system between the work area outlet and the telecom closet termination.

Litz Wire

From the German word “litzendraght”, meaning to consist of a number of separate strands that are woven or bunched together such that each strand tends to take all possible positions in the cross section of the wire as a whole. The current through each individually insulated strand is divided equally since this wire design equalizes the flux linkages and reactance of the individual strands. In other words, a litz conductor has lower AC losses than compared to solid wire conductors, which becomes important as operation frequency increases.

LMDS

Local Multipoint Distribution Service – Any service providing high-speed transmission of voice and data from single distribution points to multiple users. Generally, LMDS provides wireless broadband communications to small and medium-sized companies or to apartment buildings.

LNA

Low noise amplifier

LO

Local Oscillator

Load

A device or impedance that terminates the output of a device or transmission line. A load is typically a resistance, the magnitude of which is equal to the characteristic impedance of the transmission line.

Load Decoupling

Placement of filter components (typically mF capacitors) at the power terminals of the load in order to reduce noise.

Load Life

The minimum number of cycles the relay will make, carry, and break the specified load without contact sticking or welding, and without exceeding the electrical specifications of the device. Load life is established using various methods including Weibull probability methods.

Load Life, Rated Resistive

The voltage and current encountered by the contacts when opening and/or closing. To be considered a resistive load, the inductance in the test circuit shall not exceed an L/R ratio of 1 x 10 -4 . Load ratings are established using various methods including Weibull analysis.

Load Loss

These losses are caused by the resistance of the windings under loaded conditions.

Load Regulation

Percentage change in output voltage caused by varying the output load over a specified range (with input line, temperature, etc. remaining constant).

local area network

A privately owned, geographically limited network interconnecting electronic equipment, as in an office building to promote distributed processing and local communications.

Local Area Transport Area

LATA – (1) A geographic area established for the provision and administration of communications service. It encompasses one or more designated exchanges, which are grouped to serve common social, economic and other purposes. (2) Contiguous local exchange areas that include every point served by a LEC within an existing community of interest and that serve as the dividing line for the allocation of assets and liabilities betweenthe IXC and the LEC. (3) A telephone company term that defines a geographic area”, sometimes corresponds to an area code.

Local Loop

Refers to the physical copper pair or loop of wire from Central Office to the subscriber.

Local Oscillator

A reference signal generating circuit that is contained within a receiver or transmitter. The LO signal provides the high frequency bias to a mixer. The local oscillator signal is typically at a higher power than the signal power. An optimum local oscillator power is required to obtain low conversion loss and good RF match to the mixer non-linear impedance component. Normally optimum local oscillator powers are in the range of -3 to 13 dBm for most common diodes or FET’s.

Local sensing

Using the output terminals of the converter to provide feedback to voltage regulation circuits. Also see Remote Sensing.

locator

The device included in the design of most AMP hand crimping tools to position a terminal and assure the proper insertion depth of the stripped wire prior to crimping.

logic

The basic principles and applications of truth tables, interconnections of on-off elements, and other factors involved in digital electronics. Most AMP electronic controls use two-state gates and IC’s to perform decision making functions.

logic gate

A digital circuit with one or more inputs, and an output which depends logically on the input signal combinations. See also gate and IGFET.

Logic Inhibit/Enable

Signal (typically TTL/CMOS compatible) used to turn a power supply output on/off. Also called Remote On/Off.

Long Term Stability

Change in output voltage of a converter over time with all other factors (line, load, temp. etc.) remaining constant. Expressed as a percent, the output change is primarily due to component aging.

Longitudinal Change

The change in length of tubing when recovered. Expressed in the percent of change from the original length.

loom

Flexible tubing or sheath, usually nonmetallic, for protecting electrical wires. A cotton-braided sheath is commonly used.

loose piece

A contact (or terminal) that is produced, packaged, and terminated individually for hand application tooling.

LORAN

Long Range Navigation

Loss

Reduction in signal power.

Loss Factor

The product of the power factor and dielectric constant of an insulating material.

lossy

The property of being a poor conductor that absorbs and dissipates energy.

Lot Number

The number that identifies one production run of material. Also known as a batch number.

Low Line

Minimum value of input line voltage speified for normal converter operation.

Low Noise Amplifier

An amplifier with low noise figure that is typically used at the front end of a radio receiver.

Low Pass Filter

A reactive circuit that rejects signals whose frequencies are above the 3 dB point frequency and propagates signals whose frequencies are below the 3 dB point frequency.

low-density polyethylenes

Those polyethylenes whose density ranges from about 0.915 to 0.925. Relatively soft but tough materials.

low-level logic

Also LO logic. In digital logic, the more negative of the two logic levels in a binary system. In positive logic, a low-logic level is used to represent a logic 0, or a not-true, condition. See also high-level logic, negative logic, and positive logic.

Low-loss Dielectric

An insulating material that has a relatively low dielectric loss, such as olyethylene or Teflon.

LPF

low pass filter

LSI

large-scale integration.

Lug

A termination, usually crimped or soldered to a conductor, that allows connection to be made with a retaining screw.

lumped-element filter

A filter whose filtering elements, such as ferrite beads, consist of discrete capacitance and inductance, rather than being uniformly distributed throughout. See also distributed-element filter.