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vertical slot parallel to the coil axis (Fig. 22.17) would prevent
magnetic screening whereas a horizontal slot would hardly affect it.
So it is possible to screen both kinds of field, or either of them
alone.
In general the permeability screen is the more effective magnetic
type at low frequencies, including z.f., and the conductive screen at
high frequencies. The permeability type increases the inductance of
the enclosed inductor, especially if it is shaped so as not to be a good
conductive screen. Provided that this is not objectionable, the screen
need not be widely spaced from the inductor. A closed magnetic core
acts as a magneti