18WuD2x

346 hot-pen recorder • H scope
hot-pen recorder See THERMAL RECORDER.
hot plate A metal device, usually heated by means
of electricity, used for the purpose of conducting
certain experiments.
hot resistance The resistance of a component during
its operation (i.e., after it has been heated by
ambient temperature or internal power dissipation).
Compare COLD RESISTANCE.
hot spark A brilliant flash seen when a capacitor
discharges through a spark gap in a vacuum.
hot spot 1. In a circuit or component, an area
whose temperature is ordinarily higher than
that of the surrounding area. 2. A local current
or voltage maximum on an antenna or transmission
line. 3. In communications operations, a
geographic location in which reception is
markedly better than in other nearby places or
from which the transmitted signal appears to be
stronger.
hot-strip ammeter A current meter similar to the
hot-wire meter, except that it has a heated metallic
strip instead of a heated wire.
hot-stylus recorder See THERMAL RECORDER.
hot-tip writing The use of a heated-tip stylus in
graphic recording. Also see THERMAL RE-
CORDER.
hot-wire ammeter See HOT-WIRE METER.
hot-wire anemometer An electrical anemometer
whose indication is based on the cooling effect of
the wind on a heated filament.
hot-wire flowmeter An instrument for determining
the rate of flow of a gas in a pipe or other
channel. The circuit is similar to that of the gas
detector and hot-wire anemometer.
hot-wire gasmeter See GAS DETECTOR.
hot-wire instrument See HOT-WIRE METER.
hot-wire meter A meter in which current heats a
wire, stretching it so that it moves a pointer
across a scale over a distance proportional to the
magnitude of the current.
hot-wire microphone A microphone in which
sound waves vary the temperature of a heated
wire and, accordingly, its electrical resistance.
hot-wire relay A time-delay relay in which actuating
current heats a wire, causing it to expand,
eventually opening or closing the contacts. Also
see DELAY RELAY.
hot-wire sensor See HEATED-WIRE SENSOR.
hot-wire transducer See HOT-WIRE MICRO-
PHONE.
hour Abbreviation, h; (sometimes, hr). A unit of
time measure equal to 60 minutes or 3600 seconds.
Compare MINUTE, 1 and SECOND, 1. Also
see TIME.
housekeeping In digital-computer operations, the
part of a program that attends to chores (e.g., setting
variables to zero), rather than being involved
in making computations for a solution.
howl A discordant sound produced in headphones
or a loudspeaker, usually as a result of acoustic
or electrical feedback.
howler 1. An audio-frequency alarm device. 2. A
sound-emitting test device (see GROWLER, 1,
2).
howl repeater A form of electric feedback in
which a hum or howl occurs because of oscillation.
The term is used to describe an oscillating
conduction in a wire-communications-system
repeater.
hp Abbreviation of HORSEPOWER.
h-p Abbreviation of HIGH PRESSURE.
H pad See H NETWORK.
h parameters Parameters of the four-terminal network
equivalent of a transistor. They are hybrid
parameters (thus, h) because of their appearance
in mesh and nodal equations. The basic h parameters
are h 11 , input resistance with output shortcircuited;
h 12 , reverse voltage ratio with input
open-circuited; h 21 , forward current gain with
output short-circuited; and h 22 , output conductance
with input open-circuited.
h particle A positive hydrogen ion or proton obtained
by bombarding a hydrogen atom with alpha
particles or high-velocity positive ions.
HPF Abbreviation of highest probable frequency.
hp-hr Abbreviation of HORSEPOWER-HOUR.
HPI Abbreviation of HEIGHT-POSITION INDICA-
TOR.
H plane The plane of the magnetic field of an antenna,
or the magnetic component of an electromagnetic
field. Compare E PLANE.
H-plane bend In a waveguide, a smooth change in
the direction of the axis perpendicular to the direction
of polarization.
H-plane tee junction A waveguide tee junction,
whose structure changes in the magnetic-field
plane. Also see WAVEGUIDE JUNCTION and
WAVEGUIDE TEE.
hr Abbreviation of HOUR. (Also, h.)
H scan A radar display in which the target is represented
by two close blips, approximating a line,
whose shape is proportional to the sine of the target’s
angle of elevation.
H scope See H SCAN.