What are the cell phones?

Wireless telephone that permits telecommunication within a defined area that may include hundreds of square miles, using radio waves in the 800–900 megahertz (MHz) band. To implement a cell-phone system, a geographic area is broken into smaller areas, or cells, usually mapped as uniform hexagrams but in fact overlapping and irregularly shaped. Each cell is equipped with a low-powered radio transmitter and receiver that permit propagation of signals among cell-phone users.