“Each cell site is controlled by a mobile switching center (or ‘switch’). The switch is the brain in the network and may control as many as 100 to 200 cell sites. The voice channels at the cell sites are generally routed to the switch through land lines, and the switch connects the cellular network to the local telephone company. The switch is responsible for keeping track of the mobile call as the handset moves from one cell coverage area to another. This process is known as hand-off, and the switch tells one cell site to drop the call, tells the mobile phone to change voice channel frequencies, and tells the new cell site to pick up the call. All of this is going on without the caller being aware of the transfer (unless it doesn’t work!).