18WuD2x

esistor substitution box • resonant-line oscillator 597
resistor substitution box A self-contained assortment
of common-value resistors arranged to be
switched one at a time to a pair of terminals. In
troubleshooting and circuit development, any of
several useful fixed resistance values can thus be
obtained.
resistor transistor See ELECTRONIC RESISTOR.
resistor-transistor logic Abbreviation, RTL. A circuit
in which the logic function is performed by
resistors, and an inverted output is provided by
transistors.
resnatron
A form of vacuum tube that is used as
an oscillator and amplifier at ultra-high and microwave
frequencies. It is essentially a cavity resonator.
resolution
1. The degree to which closely adjacent
parts of an image can be differentiated. 2. The reduction
of a problem by means of logical analysis.
3. The ability of a vision or ranging system to distinguish
between objects that are close together
in terms of radial distance, direction, or absolute
separation.
resolution ratio In a television image, the ratio of
horizontal resolution to vertical resolution.
resonance 1. The state in which the natural response
frequency of a circuit coincides with the
frequency of an applied signal, or vice versa,
yielding intensified response. 2. The state in
which the natural vibration frequency of a body
coincides with an applied vibration force, or vice
versa, yielding reinforced vibration of the body.
resonance bridge An alternating-current bridge
(see BRIDGE, 2) in which one or two arms are
series-resonant or parallel-resonant, the other
arms being resistances. Also see SERIES-TYPE
RESONANCE BRIDGE and SHUNT-TYPE RESO-
NANCE BRIDGE.
resonance curve A graph of the insertion gain or
loss of a component, device, circuit, or system to
Current or voltage
Frequency
resonance curve
f 0
variations in the frequency of an applied sound or
signal. Such curves are almost always plotted in
rectangular coordinates with frequency as the independent
variable on the horizontal axis. The dependent
variable, plotted on the vertical axis, can
be any characteristic that displays a peak or dip
at the resonant frequency or frequencies. In radiofrequency
circuits, such parameters include current,
voltage, attenuation, gain, and impedance.
resonance theory of hearing The theory that
sound waves pass down the auditory canal and
cause the eardrum to vibrate. Behind the
eardrum is a system of three bones leading to the
cochlea. The cochlea consists of fibers that resonate.
Therefore, they vary in length and tension.
Various groups of fibers are activated by different
sounds, and the vibrations are transmitted to
nerves leading to the brain.
resonance radiation Electromagnetic radiation
from an energized substance, resulting from
movement of electrons from a higher to lower energy
level. When an electron moves from a higher
to a lower orbit, a photon, having a definite wavelength,
is emitted.
resonant cavity A chamber whose size reinforces
energy injected into it at a natural frequency,
which is determined by the chamber’s dimensions.
Such cavities can be used with acoustic or
electromagnetic waves.
resonant circuit A circuit whose constants are
chosen for maximum circuit response at a given
frequency. Examples: parallel-resonant circuit
and series-resonant circuit. Also see RESONANCE
and RESONANT FREQUENCY.
resonant current Current flowing in a tuned circuit
at resonance.
resonant feeder An antenna feeder that is resonant
at the operating frequency.
resonant filter A filter containing at least one series-
or parallel-resonant arm for sharp response.
Thus, a power-supply filter of this kind might
have a parallel-resonant arm acting as a wavetrap
at the ripple frequency.
resonant frequency Symbol, f r or f o . The natural
frequency at which a circuit oscillates or a device
vibrates. In an inductance-capacitance circuit
(series-resonant or parallel-resonant), the reactances
cancel at the resonant frequency, leaving
only resistance.
resonant-gate transistor A transistor embodying
a tiny tuning fork for resonance at low frequencies,
thus eliminating bulky coils and capacitors.
resonant line A transmission line that is resonant
at the operating frequency.
resonant-line amplifier See LINE-TYPE AMPLI-
FIER.
resonant-line circuit A circuit using resonant
lines as a tank. See, for example, LINE-TYPE
AMPLIFIER and LINE-TYPE OSCILLATOR.
resonant-line oscillator See LINE-TYPE OSCILLA-
TOR.