Continuous PhaseFrequency Shift Keying (CPFSK) is a variant of Frequency Shift Keying
(FSK). In contrast to the FSK method, the CPFSK method uses continuous phase shift keying. In the CPFSK method, only one fundamental is used, which is switched over in frequency. Frequency switching is performed by switching frequency-determining components on or off at the oscillator. Alternatively, a voltage controlled oscillator, a Voltage Controlled Oscillator (VCO) can be used and voltage controlled. When switching, no phase jumps are caused, no matter at which phase position this occurs. The phase position thus remains continuous.