Frequency shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete changes of a carrier wave. Usually the instantaneous frequency is switched between two discrete values. This is called binary frequency shift keying (BFSK).

In BFSK, the two binary states of the carrier signal, logic 0 and 1 are each represented by an analog waveform. Logic 0 is represented by a wave at a specific frequency, and logic 1 is represented by a wave at a different frequency. Figure 1 shows the BFSK modulation of a digital signal.

Figure 1: BFSK modulation

The students can select different data words from the FlexTrainer and observe the BFSK modulated signals on the oscilloscope. The mark and space frequencies for BFSK modulation are fixed in the firmware of FlexTrainer by the developers.