18WuD2x

386 jammer • job stream
tween or among other stations. 2. A radio operator
who engages in the practice of deliberately
JAMMING communications between or among
other stations.
jamming The deliberate use of countermeasures,
such as malicious transmission of interfering signals,
to obstruct communications.
jamming effectiveness The extent to which JAM-
MING is able to disrupt a service. It can be expressed
quantitatively as the ratio of jamming
signal voltage to jammed signal voltage. It can
also be determined according to the percentage of
data that is effectively obliterated.
JAN Abbreviation of JOINT ARMY-NAVY.
janet A system for point-to-point communication
via meteor-trail forward scatter. It is generally
used at very high frequencies (VHF).
Jansky noise Wideband, high-frequency electromagnetic
noise generated by objects in interstellar
and intergalactic space.
J antenna An end-fed half-wave antenna having a
quarter-wave, parallel-wire matching section. The
entire antenna, when oriented vertically, resembles
the letter J.
Coaxial
line
J antenna
Radiator
λ/2
Matching
section
λ/4
Janus antenna array (from Janus, an ancient Roman
god.) A Doppler-navigation antenna array
radiating forward and backward beams.
jar 1. (From Leyden jar) An obsolete unit of capacitance
equal to 1/900 microfarad. 2. The container
for the elements of a storage cell.
JASA Abbreviation for Journal of the Acoustical Society
of America.
J-carrier system In carrier-current (wired/wireless)
telephony, a broadband system that provides
12 telephone channels at frequencies up to
140 kHz.
JCET Abbreviation of Joint Council on Educational
Television.
JCL Abbreviation of job control language.
J-display A radar display having a circular time
base. The transmitted pulse and reflected (target)
pulse are spaced around the circumference; distances
can be measured circumferentially between
them.
JEDEC Acronym for Joint Electron Device Engineering
Council.
jerk The rate of change of acceleration; the third
derivative of displacement.
JETEC Acronym for Joint Electron Tube Engineering
Council.
jewel bearing A low-friction bearing used in electric
meters and other sensitive devices. It takes
its name from a jewel pivot (such as a sapphire) in
the groove of which rides the pointed end of a rotating
shaft. Also called jeweled bearing or jewel.
jezebel A passive sonobuoy used in military applications.
It detects enemy submarine noises, and
transmits them by radio to a monitoring station.
JFET Abbreviation of junction field-effect transistor.
JHG Abbreviation of JOULE HEAT GRADIENT.
jig A device constructed especially for the purpose
of holding an equipment or circuit board during
its repair.
jitter A (usually small and rapid) fluctuation in a
phenomenon, such as a quantity or wave, because
of noise, mechanical vibration, interfering
signals, or similar internal or external disturbances.
It is used especially in reference to
cathode-ray-tube (CRT) displays.
J/K Abbreviation for joule(s) per Kelvin, the SI unit
of entropy; also the unit for the Boltzmann constant.
J-K flip-flop A transistor-resistor flip-flop stage
producing an output signal even when both inputs
are in the logic 1 state (high). It is so called
because its input terminals are labeled J and K.
J/(kg•K) Abbreviation for joule(s) per kilogram
Kelvin, the SI unit of specific heat capacity.
job A unit of computer work, usually consisting of
several program runs.
job control language An operating system language
used to describe the control requirements
for jobs within the system.
job control program A program that uses control
language statements and implements them as instructions
controlling a job in an operating system.
job control, stacked See SEQUENTIAL-STACKED
JOB CONTROL.
job flow control To control the order of jobs being
processed by a computer to make the most efficient
use of peripherals and central processor
time—either manually or by an operating system.
job library A series of related sets of data that will
be loaded for a given job.
job-oriented terminal A terminal that produces
data in computer-ready form.
job statement A control statement identifying the
beginning of a series of job control statements for
a job.
job step The execution of a computer program according
to a job control statement; several job
steps can be specified by a job.
job stream In a processing system, a group of consecutively
run jobs.