frequency-shift keying(redirected from Mark frequency)
frequency-shift keying[′frē·kwən·sē ‚shift ′kē·iŋ]
A form of frequency modulation used especially in telegraph, data, and facsimile transmission, in which the modulating wave shifts the output frequency between predetermined values corresponding to the frequencies of correlated sources. Abbreviated FSK. Also known as frequency-shift modulation; frequency-shift transmission.