What is the Working principle of mobile phones?

Mobile-phones emits small amount of electromagnetic signal via the radio waves which is RF energy. Every Mobile-phone has a low power transmitter in them. While talking over the cell-phone, the transmitter takes the sound of voice & changes it into a continuous sine wave. Sine wave is measured in terms of frequency.Transmitter sends the sine wave to antenna. Antenna transmits the sine wave in the form of electromagnetic signal to the BTS. Cell-phone works by communication between service n/w through BTS or cell tower. Cell towers divide the city into small areas or cells. As the user moves from one cell to another, the signal along with the information is handed over from tower to tower.