DIGITAL CELL-PHONES (SECOND GENERATION)

They use the same radio technology as analog phones, but they use it in a different way. Analog
systems do not fully utilize the signal between the phone and the cellular network -- analog
signals cannot be compressed and manipulated as easily as a true digital signal. Digital phones
convert your voice into binary information (1s and 0s) and then compress it. This compression
allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.
Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth
over AMPS. FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly
between the two to send digital information between the cell tower and the phone. Clever
modulation and encoding schemes are required to convert the analog information to digital,
compress it and convert it back again while maintaining an acceptable level of voice quality.
Hence, digital cell phones have to contain a lot of processing power.