18WuD2x

222 dynamic range • dynatron
or noise. It is usually expressed in decibels. 2. In
a communications receiver, a measure of the
ability to receive both weak and strong signals
without excessive noise, distortion, desensitization
or other undesirable effects. It is expressed
in various ways, typically in decibels. 3. The ratio
between the loudest and faintest sounds, or between
the strongest and weakest signals, encountered
in a given environment or situation. It is
usually expressed in decibels.
dynamic rectifier tester An instrument that displays
the response curve of a rectifier on a calibrated
oscilloscope screen. During the test, the
rectifier receives an alternating-current (ac)
voltage with a low positive peak and high negative
peak, both corresponding to the rated forward
and reverse voltages (respectively) of the
rectifier. The horizontal axis of the screen indicates
voltage, the vertical axis indicates current,
and zeros for both quantities are at center
screen.
dynamic regulation In an automatically regulated
system, such as a voltage-regulated power supply,
the transient response of the system. Dynamic
regulation is determined from maximum
overshoot and recovery time when the load or line
value is suddenly changed.
dynamic regulator A circuit or device providing
dynamic regulation.
dynamic reproducer 1. See DYNAMIC MICRO-
PHONE. 2. See DYNAMIC PICKUP. 3. See DY-
NAMIC SPEAKER.
dynamic resistance See DYNAMIC IMPEDANCE.
dynamic run See DYNAMIC CHECK, 1. See also
DYNAMIC DEBUGGING.
dynamics The study of bodies, charges, fields,
forces, or pulses in motion. Compare STATICS.
dynamic sequential control In digital computer
operation, the computer’s changing the sequence
of instructions during a run.
dynamic source current See AC SOURCE CUR-
RENT.
dynamic source resistance See AC SOURCE RE-
SISTANCE.
dynamic source voltage See AC SOURCE VOLT-
AGE.
dynamic spatial reconstructor Abbreviation,
DSR. An advanced x-ray machine, developed at
the Mayo Clinic, that displays organs in threedimensional
views in motion, and allows them to
be electronically dissected without actually
operating on the patient.
dynamic speaker A loudspeaker in which a small
coil (voice coil), attached to a diaphragm or cone
and carrying an audio-frequency signal current,
moves back and forth in a permanent magnetic
field and, accordingly, causes the diaphragm or
cone to vibrate (emit sound). Compare MAG-
NETIC SPEAKER.
dynamic stability A measure of the ability of a
robot to maintain its balance while in motion.
dynamic stop As caused by a computer program
instruction, a loop indicating the presence of an
error.
dynamic storage See DYNAMIC MEMORY.
dynamic subroutine A form of computer subroutine
that allows the derivation of other subroutines
in various forms.
dynamic test See DYNAMIC CHECK.
dynamic transconductance Transconductance
determined from alternating-current (ac) signal
parameters, rather than from direct-current (dc)
parameters.
dynamic transducer A coil-and-magnet device
that converts mechanical vibration into electric
currents, or vice versa. Common examples include
most microphones, headphones, and loudspeakers.
dynamic transfer characteristic An input-output
characteristic determined, with respect to the
load of a transfer device. Also see DYNAMIC
CHARACTERISTIC.
dynamic transistor tester 1. An instrument for
checking the alternating-current (ac) gain of a
transistor, rather than its direct-current (dc)
beta. 2. An instrument for determining the condition
of a transistor from its performance in a simple
oscillator circuit. 3. An instrument that
displays a transistor response curve, or a family
of such curves, on a calibrated oscilloscope
screen. Also see DYNAMIC DIODE TESTER and
DYNAMIC RECTIFIER TESTER.
dynamo A mechanical generator of electricity; typically
a rotating machine.
dynamoelectric machinery Rotating electric machinery.
Examples: amplidynes, generators, dynamotors,
rotary converters.
dynamometer 1. See ELECTRODYNAMOMETER.
2. A device for mechanically measuring the output
power of a motor.
dynamometer ammeter See ELECTRODYNA-
MOMETER.
dynamometer voltmeter See ELECTRODYNA-
MOMETER.
dynamophone A dynamometer (see DYNAMO-
METER, 2) that uses two telephone circuits to
measure the twist of a shaft.
dynamostatic machine A machine driven by alternating-current
(ac) or direct-current (dc) power
for the generation of static electricity.
dynamotor A (usually small) self-contained
motor-generator. The motor and generator
portions are enclosed in a common housing,
giving the machine the appearance of a simple
motor.
dynaquad A pnpn four-layer semiconductor device
with three terminals, similar to the siliconcontrolled
rectifier or thyristor.
dynatron A form of vacuum tube that displays a
negative-resistance characteristic, resulting in
oscillation at ultra-high and microwave frequencies.