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LOGIC INSTRUCTION—Any instruction that executes a logic operation that is defined in symbolic
logic, such as AND, OR, NAND, or NOR [13].
LOGIC OPERATION—A nonarithmetical operation in a computer, such as comparing, selecting, making
references, matching, sorting, and merging, where the logical YES or NO quantities are involved [13].
LOGIC SWITCH—A diode matrix (See MATRIX) or other switching arrangement that is capable of
directing an input signal to one of several outputs [13].
LOGIC SYMBOL—A symbol used to represent a logic element graphically. Also a symbol used to
represent a logic operator [13].
LONGITUDINAL WAVES—Those waves in which the disturbance (back and forth motion) takes place in
the direction of propagation. Sometimes called compression waves [10].
LONG-WIRE ANTENNA—An antenna that is a wavelength or more long at its operating frequency [10].
LOOP—A 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 [10] [11].
LOOSE COUPLING—Inefficient coupling of energy from one circuit to another that is desirable in some
applications. Also called weak coupling [11].
LOWER-FREQUENCY CUTOFF—The lowest frequency a circuit will pass [9].
LOWER SIDEBAND—All difference frequencies below that of the carrier [12].
LOWEST USABLE FREQUENCY—The minimum operating frequency that can be used for
communications between two points [10].
LOW FREQUENCY—The band of frequencies from 30 kHz to 300 kHz [17].
LOW-LEVEL MODULATION—Modulation produced in an earlier stage than the final [12].
LOW-NOISE AMPLIFIER—See PREAMPLIFIER [18].
LOW-PASS FILTER—A 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 [9] [12].
LSD—See LEAST SIGNIFICANT DIGIT [13].
LUMPED CONSTANTS—The properties of inductance, capacitance, and resistance in a transmission line
[10].
LUMPED IMPEDANCE TUNING—The insertion of an inductor or capacitor in series with an antenna to
electrically lengthen or shorten the antenna [10].
MACHINE KEYING—A method of cw keying using punched tape or other mechanical means to key a
transmitter [12].
MAGIC T—See BALANCED MIXER [18].
MAGIC-T JUNCTION—A combination of H-type and E-type T-junctions [11].
