18WuD2x

variable inductor • VATE 719
Several different inductors can be connected in
series and parallel combinations, with switches
to facilitate variability. One type of variable inductor
uses a roller contact to allow continuous
adjustment. See ROLLER INDUCTOR. Another
method of varying inductance is to change the
permeability of the core, such as by moving a rod
of ferrite or powdered iron in and out of the coil.
See VARICOUPLER and VARIOMETER.
variable-pitch indication An audible signal used
in lieu of, or in conjunction with, a meter to indicate
voltage, current, logic state, etc. The higher
the value of the measured quantity, the higher
the pitch.
variable-reluctance microphone A microphone in
which the impinging sound waves cause corresponding
variations in the reluctance of an internal
magnetic circuit.
variable-reluctance pickup A phonograph pickup
in which the stylus causes an armature to vibrate
in a magnetic field, and consequently the
reluctance of the magnetic circuit varies in sympathy
with the audio frequency.
variable-reluctance transducer A transducer in
which the monitored quantity causes the reluctance
of an internal magnetic circuit to vary proportionately.
variable-resistance pickup A phonograph pickup
in which the vibration of the stylus causes the resistance
of an internal resistive element to vary in
sympathy with the sound frequency.
variable-resistance transducer A transducer in
which a monitored quantity causes the resistance
of an internal resistive element to vary proportionately.
variable-resistance tuning Tuning of a selective
resistance-capacitance (RC) circuit, such as a
Wien bridge or parallel-tee network, by varying
one or more of its resistance arms.
variable resistor A resistor whose value can be
varied either continuously or in steps. Also see
POTENTIOMETER and RHEOSTAT.
variable selectivity In a circuit or device, selectivity
that is adjustable. Example: a variableselectivity
intermediate-frequency (IF) amplifier.
variable-speed motor Any motor whose speed is
adjustable, smoothly or in steps, under load.
variable transformer A transformer (often an autotransformer)
whose output voltage is adjustable
from zero (or some minimum value) to maximum.
For this purpose, one winding (usually the secondary
in a two-winding transformer) can have a
number of taps. Smooth variation can be provided
by a wiper arm that slides over the turns of
the winding.
variable-width wound record In photographic
sound-on-film recording, a sound track made by
varying the width of the track in sympathy with
the sound variations. Compare VARIABLE-
DENSITY SOUND RECORD.
Variac See VARIABLE TRANSFORMER.
Varicap A voltage-variable capacitor of the semiconductor-diode
type. Also see VOLTAGE-
VARIABLE CAPACITOR.
varicoupler An adjustable radio-frequency transformer
consisting of a primary coil (usually the
rotor) and a secondary coil (usually the stator),
the former being rotatable to vary the coupling
between the coils. The inductance of the stator is
varied via a set of taps.
varindor A coil having a special core and whose inductance
varies with the amount of direct current
flowing through the winding. Also see SAT-
URABLE REACTOR.
variocoupler A radio-frequency transformer in
which one winding is rotatable, for the purpose of
adjusting the mutual inductance between the primary
and secondary. It is used in certain antenna-coupling
applications.
variolosser A variable attenuator.
variometer A continuously variable inductor consisting
of two coils connected in series or parallel
and mounted concentrically—one rotating inside
the other. Inductance is maximum when the coils
are perpendicular to each other, and minimum
when they are parallel.
varioplex A time-sharing method of transmitting
and receiving wire telegraph signals. It allows the
optimum usage of available lines.
varistor See VOLTAGE-DEPENDENT RESISTOR.
Varley-loop bridge A four-arm, direct-current
bridge circuit in which one of the arms, a twowire
line, is accidentally grounded at a distant
point. By adjustment of the bridge, the resulting
resistance indicates the distance to the fault.
Line A
Line B
Accidental
ground
Varley loop bridge
Lines tied
together
for test
VAR meter An instrument for measuring the apparent
(VAR) power in a reactive circuit.
varnished cambric Cotton or linen fabric in
sheets, tape or tubes, that has been varnishimpregnated
and baked. A common form of this
insulating material, the slender tubing known as
spaghetti, has largely been replaced by plastic
tubing.
varnished-cambric tubing Slender tubes of varnished
cambric slipped over bare wires and busbars
to insulate them. Also called spaghetti.
VATE Abbreviation of VERSATILE AUTOMATIC
TEST EQUIPMENT.