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 GLOSSARY OF TERMS
ABSORBER. A material which causes the irreversible conversion of the
energy of an electromagnetic wave into another form of energy, usually heat as
a result of its interactions with matter.
ABSORPTION LOSS. The attenuation of an electromagnetic wave as it passes
through a shield. This loss is primarily due to induced current and the
associated I.2-R loss.
AMBIENT LEVEL. Those levels of radiated and conducted energy existing at a
specified location and time when test sample is de-energized. Atmospheric
noise signals, both desired and undesired, from other sources and the internal
noise level of the measuring instruments all contribute to the "ambient
level".
ANTENNA. A device employed as a means for radiating or receiving
electromagnetic energy.
APERTURE.
An opening in a shield through which electromagnetic energy passes.
ATTENUATION. A general term used to denote a decrease in magnitude of power
or fields strength in transmission from one point to another caused by such
factors as absorption, reflection, scattering and dispersion. It may be
expressed as a ratio, or by extension of the term, decibels.
BLACK DESIGNATION. A designation applied to electronics components,
equipment, and systems which handle only unclassified signals, and to areas in
which no classified signals occur.
BOND. The electrical connection between two metallic surfaces established to
provide a low resistance path between them.
BOND, DIRECT. The electrical connection utilizing continuous metal-to- metal
contact between the members being joined.
BOND, INDIRECT. An electrical connection employing an intermediate electrical
conductor between the bonded members.
BONDING. The process of establishing the required degree of electrical
continuity between the conductive surfaces to be joined.
CIRCULAR MIL. A unit of area equal to the area of a circle whose diameter is
one mil (1 mil = 0.001 in.). To convert a circular mil to a square mil,
multiply by 0.7854 (1 square mil = 10.-6- square in.). The area of a
circle in circular mils is equal to the square of its diameter in mils.
COUNTERPOISE. A system of wires or other conductors usually elevated above
and insulated from the ground, forming the lower system of conductors of an
antenna. For EMP and power systems this is often an array of buried
conductors.
COMPROMISING EMANATION. Unintentional data-related or intelligence-bearing
signals which, if intercepted and analyzed, may disclose the classified
information transmitted, received, handled or otherwise processed by any
information-processing equipment.
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