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Key Terms - QRST

Radiation The emission and propagation of electromagnetic energy through free space
Reactance Opposition offered to the flow of alternating current by inductance or capacitance of a component or circuit
Reference Level A select level or amplitude associated with the top graticule line of the CRT screen. The outside reading with no shield
Reflection Loss Attenuation of the electromagnetic wave or energy caused by impedance mismatch between the wave in the air and the wave in the metal
Resistance Property of a conductor that determines the current produced by a given difference of potential (the opposition to current flow). The ohm is the unit of resistance
Resolution Bandwidth The bandwidth of the most selective amplifier/filter. Used to raise or lower the sensitivity level (ambient level) of a spectrum analyzer
Resonance The natural, sympathetic vibration of a volume of air or a panel of material at a particular frequency as a result of excitation by a sound of that particular frequency
Reverberation The persistence of sound within a space after the source has ceased
Reverberation Time The time in seconds required for sound to decay to inaudibility after the source ceases (the time in seconds for the sound level at a specific frequency to decay 60 dB)
RF Attenuator A device which reduces the amplitude of an input signal

SCIF Secure Compartmented Information Facility; relates to DCID 6/9
Sensitivity Measure of a spectrum analyzer's ability to display minimum level signals, at a given IF bandwidth, display mode, and any other influencing factors and expressed in decibels
Shield A metallic configuration inserted between a source and the desired area of protection which has the capability to reduce the energy level of a radiating electromagnetic field by reflecting and absorbing the energy contained in the field
  A metallic partition placed between two regions of space. It is used to control the propagation of electric, magnetic, and planewave fields from one of the regions to the other
Shield Effectiveness A measure of the reduction or attenuation in electromagnetic field strength at a point in space caused by the insertion of a shield between the source and that point. Usually stated in dB.
  S.E. = 20 LOG10 (E1/E2) Decibels
Shielded Enclosure An area (box, room, building) specifically designed to attenuate electromagnetic radiation or electromagnetic radiation and acoustical emanations, originating either inside or outside the area. Necessary openings in a shielding enclosure, such as doors, air vents, and electrical feed-thrus, are specially designed to maintain this attenuation
Sound Absorption Coefficient The dimensionless ratio of sound energy absorbed by a given surface to that incident upon the surface; designated by a lower-case "a"
Sound Transmission Class A single number rating system which compares the Sound Transmission Loss of a test specimen with a standard contour
Sound Transmission Coefficient The ratio of sound transmitted through a partition to that incident upon the partition; designated by a lower-case "t"
Structure-Borne Noise Generation and propagation of time-dependent motions and forces in solid materials which result in unwanted radiated sound
Structure-Borne Sound Sound energy transmitted through the solid media of the building structure
Susceptibility Measure of the degradation of performance of a system when exposed to an electromagnetic environment

Tempest A code word (not an acronym) which encompasses the government/industrial program for control of static charge, noise, and interference from systems processing classified data. Individual equipment may be "Tempested" or commercial equipment may be placed in shielded enclosures
Tesla (T) A unit of magnetic flux density
Tinning Coating of a terminal, lead, or conductive pattern with tin or solder to improve or maintain solderability, or to aid in the soldering operation
  Coating of shielding materials with tin or solder to enable the connection of dissimilar metals
Tuned Dipole A dual rod antenna used to radiate planewaves where the elements of the antenna are tuned to half of the wavelength for maximum gain

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Information presented is subject to change as product enhancements are made. Contact ETS-Lindgren Sales Department for current specification.