Frequency-shift keying (FSK) is a frequency
modulation scheme in which digital information is transmitted
through discrete frequency changes of a carrier wave.
The simplest FSK is binary FSK (BFSK). BFSK literally implies using a pair of
discrete frequencies to transmit binary (0s and 1s) information. With this
scheme, the "1" is called the mark frequency and the "0" is
called the space frequency.
