In facsimile, a frequency modulationsystem where one frequency represents picture black and another frequency represents picture white[?]. Frequencies between these two limits may represent shades of gray
An intentional frequency change used for modulation purposes
... da Gama, (1469?-1524), first to reach India from Europe by the sea route
Thomas Gann[?], explorer
Pierre Gaultier de Varennes et de la Vérendrye, (1685-1749), ...