Physics Cell Phone Question...explain?

Question

What is frequency shift keying?

A. method of coding voice sounds
B. method of sending digital information on radio
C. method of sending voice on the internet
D. method of coding music on an MP3
E. Apple's method of digital recording

Answer 1

Frequency-shift keying (FSK) is a form of frequency modulation in which the modulating signal shifts the output frequency between predetermined values.

Look at :
http://en.wikipedia.org/wiki/Frequency-shift_keying