Popular analog modulation techniques include amplitude modulation and frequency modulation. A modulator is a device that performs modulation. VCOs are used in analog applications such as frequency modulation and frequency-shift keying. Range demodulation is limited to 1/4 wavelength of the transmit modulation. FRS uses frequency modulation (FM) instead of amplitude modulation (AM). That limit depends upon the type of modulation and demodulation. Regeneration, the superheterodyne circuit and wide-band frequency modulation or FM. It also helps in frequency modulation of waves. Compare to the modulation index for frequency modulation. Both ASK modulation and demodulation processes are relatively inexpensive. Originally, Gaussian frequency-shift keying (GFSK) modulation was the only modulation scheme available. This is the basis of pulse width modulation. These cards used FM synthesis, which generates sound through modulation of sine waves. G.703 provides specifications for pulse code modulation (PCM). The term digital baseband modulation (or digital baseband transmission) is synonymous to line codes.