18WuD2x

decade counter • decimal code 171
decade counter A counter (see COUNTER, 1, 2) in
which the numeric display is divided into
sections, each having a value 10 times that of the
next and displaying a digit from zero to nine.
decade inductor An inductor whose value is variable
in 10 equal steps. Compare DECADE CA-
PACITOR and DECADE RESISTOR.
decade resistor A resistor whose value is variable
in 10 equal increments. Compare DECADE CA-
PACITOR and DECADE INDUCTOR.
decade scaler A scale-of-10 electronic counter
(i.e., a circuit delivering one output pulse for each
group of 10 input pulses).
decametric waves Waves in the 10- to 100-meter
band (30 to 3 MHz).
decay 1. The decrease in the value of a quantity,
e.g., current decay in a resistance-capacitance
circuit. 2. The gradual, natural loss of radioactivity
by a substance.
decay characteristics 1. The decay of a parameter;
usually an exponential function. 2. The persistence
time in a storage oscilloscope.
decay curve A curve, usually logarithmic, representing
the function of quantity versus time for a
signal decrement, the decrement of radioactivity,
or other natural process.
decay rate
A quantitative expression for the rapidity
with which a quantity decreases. Generally
listed in decibels per second (dB/s) or decibels
per millisecond (dB/ms).
decay time The time required for pulse amplitude
to fall from 90% to 10% of the peak value. Also
called FALL TIME.
Decca A 70- to 130-kHz CW radio navigation system
(British).
decelerated electron A high-speed electron that is
abruptly decelerated upon striking a target, causing
X-rays to be emitted.
decelerating electrode A charged electrode that
slows the electrons in an electron beam.
deceleration Acceleration that results in a decrease
in speed.
deceleration time 1. The time taken by magnetic
tape to stop moving after the last recording or
playback has finished. 2. The time taken by a
mechanical data storage medium, such as
a hard disk, to come to rest after completion
of a read or write operation, or on poweringdown.
decentralized data processing Data processing in
which the computing equipment is distributed
among managerial subgroups.
deception A method of producing misleading
echoes in enemy radar.
deception device A radar device, or radar-associated
device, for deception.
deci- Abbreviation, d. A prefix meaning one-tenth
(10 –1 ). Examples: DECIBEL, DECIMETER.
decibel Abbreviation, dB. A practical unit of relative
gain. In terms of power, the relative gain in
decibels is equal to:
Gain (dB) = 10 log 10 (P out /P in ),
where P out is the output power and P in is the input
power. For voltage, if the input and output
impedances are the same, the gain in decibels is
given by:
Gain (dB) = 20 log 10 (V out /V in ),
where V out is the output voltage and V in is the input
voltage. For current, if the input and output
impedances are the same, the gain in decibels is
given by:
Gain (dB) = 20 log 10 (I out /I in ),
where I out is the output current and I in is the input
current. Losses are indicated by negative dB gain
values.
decibels above reference acoustic power Abbreviation,
dBrap. The ratio of a given acoustic
power level to a lower reference acoustic power
level, specified in decibels.
decibels above reference noise Abbreviation,
dBrn. The ratio of the noise level at a selected
point in a circuit to a lower reference noise level,
in decibels.
decibels referred to 1 millivolt Abbreviation,
dBmV. The relative voltage level of a signal when
compared with a 1-mV signal measured at the
same terminals.
decibels referred to 1 milliwatt Abbreviation,
dBm. The ratio, in decibels, of an applied power
level to the power level of 1 mW.
decibels referred to 1 volt Abbreviation, dBV. The
ratio, in decibels, of a given voltage to 1 V, expressed
in decibels.
decibels referred to 1 watt Abbreviation, dBW.
The ratio of a given power level to the power level
of 1 W, expressed in decibels.
decider See DECISION ELEMENT.
decigram A unit of mass equal to 0.1 gram.
deciliter A unit of volume equal to 0.1 liter, or 10 –4
cubic meter.
decilog A unit equal to 0.1 times the common logarithm
of a ratio.
decimal 1. Pertaining to the base-10 number system
(see DECIMAL NUMBER SYSTEM). 2. A
base-10 numerical fraction, represented by figures
to the right of the radix point (decimal point),
and arranged serially according to negative
powers of 10. Examples: 0.12 = 1.2 × 10 –1 ,
0.00135 = 1.35 × 10 –3 .
decimal attenuator An attenuator circuit whose
resistances are chosen for attenuation in decimal
steps. Thus, one section provides attenuation
in steps of 0.1 times the applied voltage,
another in steps of 0.01 times the applied voltage,
another in steps of 0.001 times the applied
voltage, etc.
decimal code A method of defining numbers, in
which each place has a value of ten times that immediately
to the right.