18WuD2x

582 random noise • ratio detector
random noise Electrical noise in which the pulses
or fluctuations have no discernible pattern of occurrence
(i.e., they are haphazard in frequency
and amplitude).
random number A number derived by chance. It is
used in statistical analysis for various purposes.
random number generator Hardware or software
that provides a sequence of numbers or digits
that are random for the purpose of a given statistical
application.
random occurrence See CHANCE OCCURRENCE.
random variable In statistics, a variable that can
have a number of values, each of the same probability.
random winding A coil winding in which the turns
are wound haphazardly to reduce distributed capacitance.
range 1. The limits within which a circuit or device
operates (i.e., the territory defined by such limits).
Examples: current range, frequency range,
and voltage range. 2. The difference between the
upper and lower limits of deflection of a meter.
3. The distance over which a transmitter operates
reliably. 4. A clear area for testing antennas.
5. The distance between a radar station and a
target. 6. The possible values for a quantity or
function that lie between given limits.
range capacitor See TRIMMER CAPACITOR.
range-height indicator Abbreviation, RHI. A radar
display in which the horizontal axis shows distance
to the target, and the vertical axis shows elevation
of the target.
range mark See DISTANCE MARK.
range plotting The creation of a graph of the distance
(range) to objects, as a function of direction
or orientation in two or three dimensions. Commonly
used in robot guidance systems.
range resistor See TRIMMER RESISTOR.
range sensing The measurement of distances to
objects via electronic methods such as radar,
sonar, vision systems, etc. Commonly used in
robot guidance systems.
ranging 1. Any means of determining the distance
from a station or vehicle to an object or objects.
2. Any of several methods for a vehicle, vessel,
aircraft, spacecraft, or robot to navigate in its environment
by measuring, and keeping track of
changes in, the distance between itself and one or
more objects or beacons.
rank 1. To arrange in a specific sequence according
to significance. 2. A place in such a sequence.
Rankine scale A temperature scale on which the
freezing point of water is 491.69 degrees, and the
boiling point 671.69 degrees. Absolute zero is
represented by 0 degrees. For conversion to
kelvins, multiply degrees Rankine by 5/9.
rapid drift A fast change of a quantity or setting
(usually in one direction) with time.
rapid printer See QUICK PRINTER.
raser A device that produces coherent electromagnetic
waves at radio frequencies; the radiofrequency
equivalent of a LASER.
raster The rectangle of light (composed of unmodulated
lines) seen on the screen of a television
picture tube when no signal is present.
ratchet circuit See COMMUTATOR, 2 and ELEC-
TRONIC RATCHET.
rate action See DERIVATIVE ACTION.
rate effect In a four-layer semiconductor device,
the tendency for the switch to conduct undesirably
as a result of a transient spike.
rate-grown transistor See GRADED-JUNCTION
TRANSISTOR.
rate gyro A special gyroscope for measuring angular
rates.
rate of change 1. The extent to which the value of
a dependent variable changes in accordance with
a specified change in an independent variable
(usually time). 2. A quantitative expression of the
speed with which a dependent variable changes,
with respect to an independent variable (usually
time).
rate signal A signal whose amplitude is proportional
to the derivative of a variable, with respect
to time.
rate time In automatic-control operations, the
time over which the addition of DERIVATIVE AC-
TION advances PROPORTIONAL ACTION.
ratio-arm bridge A simple four-arm bridge in
which the balancing potentiometer supplies the
two arms, one on each side of the slider at all
settings.
R x
Det
R s
R a R b
R x = R a
R b
R s
ratio-arm bridge
ratio arms Two impedance arms serving to establish
the numerical ratio of a bridge circuit.
ratio control In automatic-control operations, a
system in which the controlled variable is in a
prescribed ratio to another variable.
ratio detector A frequency-modulation (FM) second
detector resembling the FOSTER-SEELEY
DISCRIMINATOR, except that one of the two