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J 1. Abbreviation for JOULE. 2. Symbol for JACK
or CONNECTOR. 3. Symbol for EMISSIVE
POWER.
j (j operator) The square root of –1; an imaginary
number (usually denoted i in mathematics). Assigned
to reactance values depicted on the vertical
axis of the resistance-reactance (RX) plane in
impedance vector diagrams, and whose currents
are 90 degrees out of phase with the current in
the resistive part of an alternating-current circuit.
jack A receptacle for a plug. A plug (a male connector)
is inserted into a jack (a female connector) to
complete a circuit or removed from it to break a
circuit.
jack
ing outer case or wrapper on a component, such
as a capacitor. 3. A shield can or shield box. 4. A
heat-radiating or water-conducting enclosure
used in cooling a power vacuum tube.
jack panel A (usually metallic) panel in which a
number of jacks are mounted, usually in some
order or sequence as denoted by labels.
jack box A (usually metallic) box or can used to
hold, shield, or protect a jack or group of jacks.
jacket 1. The outer covering on a cable, as opposed
to the insulation or dielectric separating the individual
conductors within the cable. 2. An insulatjack
panel
jackscrew In a two-piece connector, a screw for
mating or separating the halves of the connector.
Jacob’s law A principle concerning the behavior of
motors. An electric motor develops maximum
power when E i = 2E bk , where E i is the applied voltage
and E bk is the back voltage.
JAES Abbreviation for Journal of the Audio Engineering
Society.
jaff Colloquial term for radar jamming that combines
electronic and chaff techniques.
jag Distortion caused by temporary loss of synchronization
between the scanner and recorder in
a facsimile system.
jam input 1. A means of setting a logic line to the
desired condition by directly applying the desired
high or low voltage. 2. A voltage applied to a logic
line to force it high or low.
jammer 1. A radio transmitter or station used for
the purpose of JAMMING communications be-
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