LOGIC INSTRUCTIONAny instruction that executes a logic operation that is defined in symbolic
logic, such as AND, OR, NAND, or NOR .
LOGIC OPERATIONA nonarithmetical operation in a computer, such as comparing, selecting, making
references, matching, sorting, and merging, where the logical YES or NO quantities are involved .
LOGIC SWITCHA diode matrix (See MATRIX) or other switching arrangement that is capable of
directing an input signal to one of several outputs .
LOGIC SYMBOLA symbol used to represent a logic element graphically. Also a symbol used to
represent a logic operator .
LONGITUDINAL WAVESThose waves in which the disturbance (back and forth motion) takes place in
the direction of propagation. Sometimes called compression waves .
LONG-WIRE ANTENNAAn antenna that is a wavelength or more long at its operating frequency .
LOOPA curved conductor that connects the ends of a coaxial cable or other transmission line and
projects into a waveguide or resonant cavity for the purpose of injecting or extracting energy  .
LOOSE COUPLINGInefficient coupling of energy from one circuit to another that is desirable in some
applications. Also called weak coupling .
LOWER-FREQUENCY CUTOFFThe lowest frequency a circuit will pass .
LOWER SIDEBANDAll difference frequencies below that of the carrier .
LOWEST USABLE FREQUENCYThe minimum operating frequency that can be used for
communications between two points .
LOW FREQUENCYThe band of frequencies from 30 kHz to 300 kHz .
LOW-LEVEL MODULATIONModulation produced in an earlier stage than the final .
LOW-NOISE AMPLIFIERSee PREAMPLIFIER .
LOW-PASS FILTERA filter that passes a majority of the low frequencies on to the next circuit and
rejects, or attenuates, the higher frequencies. Also called a high-frequency discriminator  .
LSDSee LEAST SIGNIFICANT DIGIT .
LUMPED CONSTANTSThe properties of inductance, capacitance, and resistance in a transmission line
LUMPED IMPEDANCE TUNINGThe insertion of an inductor or capacitor in series with an antenna to
electrically lengthen or shorten the antenna .
MACHINE KEYINGA method of cw keying using punched tape or other mechanical means to key a
MAGIC TSee BALANCED MIXER .
MAGIC-T JUNCTIONA combination of H-type and E-type T-junctions .