NONDEGENERATIVE PARAMETRIC AMPLIFIERA parametric amplifier that uses a pump signal
frequency that is higher than twice the frequency of the input signal .
NONDIRECTIONALSee OMNIDIRECTIONAL .
NONLINEAR DEVICEA device in which the output does not rise and fall in direct proportion to the
input   .
NONLINEAR IMPEDANCEAn impedance in which the resulting current through the device is not
proportional to the applied voltage .
NONLUMINOUS BODIESObjects that either reflect or diffuse light that falls upon them .
NONRESONANT LINEA transmission fine that has no standing waves of current or voltage .
NONTRIP-FREE CIRCUIT BREAKERA circuit breaker that can be held in the ON position during an
overcurrent condition .
NORA logic function of A and B that is true if both A and B are false .
NOR GATEAn OR gate that is followed by an inverter to form a binary circuit in which the output is a
logic 0 if ANY of the inputs is a logic 1 and the output is a logic 1 only if ALL the inputs are a logic 0
NORMALThe imaginary line perpendicular to the point at which the incident wave strikes the reflecting
surface. Also called the perpendicular .
NOT CIRCUITA binary circuit with a single output that is always the opposite of the input. Also called
an INVERTER CIRCUIT .
NPNAn NPN transistor is formed by introducing a thin region of P-type material between two regions of
N-type material .
NULLOn a polar-coordinate graph, the area that represents minimum or 0 radiation .
NUMBER(1) A mathematical entity that may indicate quantity or amount of units. (2) Loosely, a
numeral. An abstract mathematical symbol for expressing a quantity. In this sense, the manner of
representing the number is immaterial. Take 26, for example; this is its decimal form - but it could be
expressed as a binary (base 2), octal (base 8), or hexadecimal (base 16) number .
NUMBER REPRESENTATIONThe representation of numbers by agreed sets of symbols according to
agreed rules .
NUMBER SYSTEMLoosely, a number representation system. Any system for the representation of
numbers (see POSITIONAL NOTATION) .
NUMERAL(1) A discrete representation of a number. For example, twelve, 12, XII, 11002 are four
different numerals that represent the same number. (2) A numeric word that represents a number .
NUTATINGMoving an antenna feed point in a conical pattern so that the polarization of the beam does
not change .
OCTAL NUMBER SYSTEMA number system based on powers of eight. This system is used
extensively in computer work .