  300px|thumb|right|an example of binary fsk frequency-shift keying (fsk) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave., p 509 the simplest fsk is binary fsk (bfsk). bfsk uses a pair of discrete frequencies to transmit binary (0s and 1s) information.fsk: signals and demodulation (b. watson) http://www.xn--sten-cpa.se/share/text/tektext/digital-modulation/fsk_signals_demod.pdf 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 to the right. == implementations of fsk modems == reference implementations of fsk modems exist and are documented in detail.teaching dsp through the practical case study of an fsk modem (ti) http://www.ti.com/lit/an/spra347/spra347.pdf the demodulation of a binary fsk signal can be done using the goertzel algorithm very efficiently, even on low-power microcontrollers.fsk modulation and demodulation with the msp430 microcontroller (ti) http://www.ti.com/lit/an/slaa037/slaa037.pdf == other forms of fsk == ===minimum-shift keying===  minimum frequency-shift keying or minimum-shift keying (msk) is a particular spectrally efficient form of coherent fsk. in msk, the difference between the higher and lower frequency is identical to half the bit rate. consequently, the waveforms that represent a 0 and a 1 bit differ by exactly half a carrier period. the maximum frequency deviation is Î´&nbsp;=&nbsp;0.25&nbsp;fm, where fm is the maximum modulating frequency. as a result, the modulation index m is 0.5. this is the smallest fsk modulation index that can be chosen such that the waveforms for 0 and 1 are orthogonal. a variant of msk called gmsk is used in the gsm mobile phone standard. === audio fsk === audio frequency-shift keying (afsk) is a modulation technique by which digital data is represented by changes in the frequency (pitch) of an audio tone, yielding an encoded signal suitable for transmission via radio or telephone. normally, the transmitted audio alternates between two tones: one, the "mark", represents a binary one; the other, the "space", represents a binary zero. afsk differs from regular frequency-shift keying in performing the modulation at baseband frequencies. in radio applications, the afsk-modulated signal normally is being used to modulate an rf [[carrier wave|ca
Quantized_radio_modulation_modes