18WuD2x

electron gun • electronic counter 245
a vacuum. In a cathode-ray tube, the gun comprises
a heated cathode, control electrode, accelerating
electrodes, and a focusing electrode.
electron-hole pair In a semiconductor, an electron
and a related hole. Each electron in the conduction
band has a counterpart in the valence band,
a vacancy (hole) left by the electron’s moving to
the conduction band.
Hole
Nucleus
Electron
electron-hole pair
Valence band
Conduction
band
electronic 1. Descriptive of any component, device,
or system that functions, according to the
principles of ELECTRONICS. 2. Pertaining to
electrons.
electronic adder A circuit (such as an operational
amplifier) for performing arithmetic addition. In
such a circuit, the output-signal amplitude is the
sum of the input-signal amplitudes. Also see
ADDER and ANALOG ADDER.
electronic aid An electronic device or circuit that
contributes to the operation of a nonelectronic
device or system; a pH meter, for example, is an
electronic aid to chemistry.
electronics aide See ELECTRONICS TECHNICIAN.
electronic attenuator An attenuator in which the
variable resistor is the output section of an active
device, such as a transistor. Varying the directcurrent
(dc) bias of the input section varies the
resistance of the output section.
electronic autopilot A servo system for detecting
and automatically correcting an aircraft’s flight
path.
electronic balance An electronic scale, which uses
a sensitive current-measuring device in conjunction
with a movable tension device.
electronic brain 1. A high-end computer. 2. A
robot controller. 3. A system that possesses or
uses artificial intelligence (AI).
electronic breadboard 1. A thin, usually nonmetallic
board or card having prepunched holes
for the quick assembly of electronic circuits for
test and evaluation. 2. Any circuit prototype that
is manually wired during the experimental phase
of product development.
electronic bug 1. A semiautomatic telegraph key
that produces dots via an oscillating mechanical
arm. The operator produces dashes manually.
2. A telegraph keying device that automatically
generates dots and dashes. Also see ELECTRONIC
KEY, 1. 3. An undetermined source of problems
or improper operation in an electronic circuit.
electronic buzzer 1. A mechanical buzzer driven
by a direct-current (dc) amplifier. 2. An oscillator
circuit that produces a sound similar to that of a
mechanical buzzer.
electronic calculating punch A machine that
punches on a card the result of calculations it
has performed on data it has read from another
punched card.
electronic calculator A fully electronic machine
for performing mathematical calculations. The
simplest machines perform basic arithmetic;
more sophisticated ones can do operations with
trigonometric, logarithmic, hyperbolic, and other
scientific functions. Basic machines are available
in department stores for about five dollars. It is
usually powered via a small cell or battery, or by
a small photovoltaic panel.
electronic camouflage The use of electronics by a
target craft to minimize or prevent the reflection
of radar echoes.
electronic carillon An electronic system that produces
sounds resembling those of a bell carillon.
electronic chime See ELECTRONIC CARILLON.
electronic circuit An electric circuit containing
active electronic components, such as transistors
and integrated circuits, as opposed to a circuit
containing only passive electrical components
(such as resistors, switches, heating elements,
etc.).
electronic clock 1. An electric clock whose motor
is driven by a constant-frequency oscillator (crystal
or tuning fork type), followed by multivibrators
and amplifiers. 2. Any electronic timing circuit
that produces pulses at predetermined intervals
for the purpose of regulating the operation of
other circuits, subsystems, or assemblies.
electronic commutator See COMMUTATOR, 2.
electronic conduction A flow of electric current
resulting from the movement of electrons among
atoms in a conductor.
electronic control 1. The science of automatically
controlling machines and devices by means of
electronic circuits. 2. A circuit or device that provides
automatic electronic control.
electronic controller A controller (see CON-
TROLLER, 2) having no moving parts. For automatic
operation, such a device often contains a
circuit that senses control signals, compares
them with a signal standard, and automatically
adjusts the output control power accordingly.
electronic counter A fully electronic circuit that
indicates the number of pulses that have been