lock and key protection system[A] protection system that involves matching a key or password with a specific access requirement. [INFOSEC-99]
lock-in frequencyA frequency at which a closed-loop system can acquire and track a signal. See lock-in range.
lock-in rangeThe range of frequencies within which a closed-loop system can acquire and track a signal. 2.
locked modeA mode in which BitLocker Drive Encryption prevents access to the encrypted drive, either because the system components have changed or because it needs…
LockoutLockout means a labor dispute involving a work stoppage, wherein an employer withholds work from its employees in order to gain a concession from them.
log-offThe procedure that is followed by a user in closing a session, e.g., a period of terminal operation. Synonym log out.
log-periodic (LP) antennaA broadband, multi-element, unidirectional, narrow-beam antenna that has impedance and radiation characteristics that are regularly repetitive as a…
logical link control (LLC) sublayerIn a local-area-network/metropolitan-area-network (LAN/MAN) system, the part of the link level that (a) supports medium-independent data link functions…
logical signaling channelA logical channel that provides a signaling path within an information channel or within a physical signaling channel.
logical topologyOf a network, the schematic configuration that reflects the network's function, use, or implementation without regard to the physical interconnection of…
loginThe procedure that is followed by a user in beginning a session, e.g., a period of terminal operation. Synonym logon.
long lineA transmission line in a long-distance communications network. Note: Examples of long lines are TDM and FDM carrier systems, microwave radio links…
long silent intervalA silent interval during a ringing cycle or pattern that lasts at least 1200 ms. [T1.401-1998]
long wavelengthIn fiber optic communications, pertaining to optical wavelengths greater than 1 m.
long-distance callAny telephone call to a destination outside the local service area of the calling station, whether inter-LATA or intra-LATA, and for which there is a…
long-haul communicationsIn public switched networks, pertaining to circuits that span large distances, such as the circuits in inter-LATA, interstate, and international…
long-term bit error rateBit error rate measured over a sufficiently long period, for example, one month. [T1.226-1992]
long-term stabilityOf an oscillator, the degree of uniformity of frequency over time, when the frequency is measured under identical environmental conditions, such as supply…
longitudinal balanceThe electrical symmetry, with respect to ground, of the two wires of a pair 2. An expression of the difference in impedance of the two sides of a circuit.
longitudinal balance-audioThe ratio of the disturbing longitudinal source voltage, Vs, and the resultant metallic voltage, Vm, at the same frequency of the network under test…
longitudinal voltageA voltage induced or appearing along the length of a transmission medium. Note 1: Longitudinal voltage may be effectively eliminated by using differential…
loop closureA condition in which the network presents a low-resistance tip-to-ring dc path at the network interface (NI). [T1.407-1990]
loop compensation lossThe loss that could be provided by a digital loop carrier system or a fiber-in-the-loop system when a short customer analog access cable results in…
loop filterIn a phase-locked loop, a filter located between the phase detector (or time discriminator) and the voltage controlled oscillator (or phase shifter).
loop gainThe total usable power gain of a carrier terminal or two-wire repeater. Note: The maximum usable gain is determined by, and may not exceed, the losses in…
loop noiseThe noise contributed by one or both loops of a telephone circuit to the total circuit noise.
loop openA signal in which the network applies a high resistance between the tip and ring conductors at the network interface (NI). [T1.407-1997]
loop startA supervisory signal given by a telephone or PBX in response to completing the loop path.
loop testA test that uses a closed circuit, i.e., loop, to detect and locate faults.
loop transmissionMultipoint transmission in which (a) all the stations in a network are serially connected in one closed loop, (b) there are no cross-connections, (c) the…
loop-backA method of performing transmission tests of access lines from the serving switching center, which method usually does not require the assistance of…
looped dual busA distributed-queue dual-bus (DQDB) scheme in which the head-of-bus functions for both buses are at the same location.
LoranLong Range Navigation, a system of long range navigation whereby latitude and longitude are determined from the time displacement of radio signals from…
loran stationA long distance radionavigation land station transmitting synchronized pulses. Hyperbolic lines of position are determined by the measurement of the…
LossThe amount an insurance company pays on a claim.
Loss DeviationThe term "Loss Deviation" denotes the variation of the actual loss from the designed value.
lossless compressionExact construction of image, bit-by-bit, with no loss of information.
lossy compressionReduces storage size of image by reducing the resolution and color fidelity while maintaining minimum acceptable standard for general use.
lossy mediumA medium in which a significant amount of the energy of a propagating electromagnetic wave is absorbed per unit distance traveled by the wave. [After 2196]
lost blockA block not delivered to the user within a specified maximum end-to-end block transfer time.
lost callA call that has not been completed for any reason other than cases where the call receiver (termination) is busy.
lost frameA frame that is not delivered to the destination user within an agreed-upon measurement period, and the network is responsible.
low-level modulationModulation of a signal, e.g., a carrier, at a point in a system or device, such as a radio transmitter, where the power level is low compared to the final…
low-level signalingThe use on signal lines of voltage levels that are between the limits of positive and negative 6 volts. Synonym low-level keying.
low-pass filterA filter network that passes all frequencies below a specified frequency with little or no loss, but strongly attenuates higher frequencies.
low-performance equipmentEquipment that has imprecise characteristics that do not meet system reliability requirements. 2.
low-power communication deviceA restricted radiation device, exclusive of those employing conducted or guided radio frequency techniques, used for the transmission of signs, signals…
lowest usable high frequency (LUF)The lowest frequency in the HF band at which the received field intensity is sufficient to provide the required signal-to-noise ratio for a specified time…
LPAbbreviation for linear programming, linking protection.
luminance range1. In CRT displays, the difference in brightness between the lightest and the darkest element of a scene or its display. [After SMPTE] 2.
luminance signal1. In television technology, the signal that describes (a) the distribution of brightness levels within the image and (b) the equation for deriving that…
lurkerIn the Internet, a participant in a chat room or a subscriber to a mailing list or newsgroup who passively observes but does not actively participate in…
lurkingPassive participation in (i.e., monitoring) the activities of a mailing list, a newsgroup, an IRC channel, a video connection, or any other Internet…
lynxA World Wide Web browser that provides a character-based user interface to hypertext-based information.