Frequency Shift Keying

Frequency-shift keying (FSK) is a modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. The most common form of frequency shift keying is 2-FSK. As suggested by the name, 2-FSK uses two discrete frequencies to transmit binary (0's and 1's) information. With this scheme, the "1" is called the mark frequency and the "0" is called the space frequency. The time domain of an FSK modulated carrier is illustrated in the figures at right.
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Frequency modulation in which the modulating signal shifts the output frequency between predetermined values. (188 ) Note 1: Usually, the instantaneous frequency is shifted between two discrete values termed the "mark" and "space" frequencies. This is a noncoherent form of FSK. Note 2: Coherent forms of FSK exist in which there is no phase discontinuity in the output signal. Synonyms frequency-shift modulation, frequency-shift signaling.

<communications> (FSK) The use of frequency modulation to transmit digital data, i.e. two different carrier frequencies are used to represent zero and one.
FSK was originally used to transmit teleprinter messages by radio (RTTY) but can be used for most other types of radio and land-line digital telegraphy. More than two frequencies can be used to increase transmission rates.
(1997-07-14)

frequency-shift keying