In Quadrature Frequency Shift Keying (QFSK) there are two bits yielding four different combinations.

Quadrature Frequency Shift Keying

In QFSK, the binary states of the carrier signal are divided into blocks of two-bit. There are four possible combinations 00, 01, 10, 11 of two bits. Therefore there will be four different symbols, each representing a different block. A different carrier frequency is assigned to each of the four symbols.

Figure 1: QFSK modulation

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