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authorities.
MPR-II
The standard originally proposed by the Swedish National Board of Measurement and Testing. It
set maximum levels of electromagnetic radiation emitted by monitors, and has now been adopted
as a world standard. MPR-II defines maximum permitted electrostatic, magnetic and electric field
levels measured at a distance of 50 cm from the center of the monitor (see table).
TCO
In 1991, the Swedish Tjänstemannens Central Organization (TCO, Swedish confederation of
Professional Employees ) set a standard even more severe than MPR-II, especially for
alternating electric fields (AEF). The TCO standard is more severe since not only are the
permitted field levels reduced compared with MPR-II, but the measuring distance is also reduced
(see table).
Electromagnetic radiation standards
EMI (Electrical Magnetic Interference)
The electrical and/or magnetic radiation coming from the working electrical or electronic
equipment.
EMS (Electrical Magnetic Sustainment)
The ability of electrical or electronic equipment to function properly in the environment with
electrical and/or magnetic interference.
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F
Flicker
Very rapid variations in picture intensity caused by the finite time required for the electron beam
to scan a picture onto the screen. Two kinds of flicker occur: line flicker caused by the electron
beam scanning-in each line of the picture; and frame flicker (or field flicker if the picture is
interlaced) caused by the frame repetition rate of 50 frames/second. Frame flicker is noticeable
with GUI and DTP software (which have a light background), and can be very disturbing,
especially for those who work regularly with displays - contributing to eye strain, headaches,
visual blurring, stress, etc. The problem can, however, be eliminated by increasing the refresh
rate (number of frames/second) of the monitor to a value above around 70 Hz. Sensitivity to
flicker appears to diminish with increasing age.
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H
Hertz
The unit of frequency named after the physicist Heinrich Hertz (1857-1894). 1 hertz (Hz) is equal
to 1 cycle/second.