How Cellular Phones Work

Cell phones Operate Using Radio Frequencies
Cellular devices operate using radio frequencies much in the same way CB radios and walkie-talkies communicate, using radio signals in a certain frequency. For example AT&T Wireless devices operate using an 850Mhz frequency, while Verizon and Sprint Wireless use the 1900Mhz and 2100Mhz frequencies.

Communicating With Cell Phone Towers
Cellular devices send out a signal to cellular towers and look for signals from those towers. The tower therefore must be operating on the same frequency as the cell phone, for example 850Mhz for AT&T phones. By operating on the same frequencies, your device and the cellular towers are easily able to communicate. Once your call is connected to a tower, the call is then transmitted through a land line connection (Typically T-1 or fiber optic cables) found at the tower to its final destination. For example, you make a call in San Diego, the tower you are closest to you picks up your signal and sends it via landline to Montreal, where the call is delivered to the person you are calling. If the person you are calling also is using a cell phone, his phone's base station will receive the call and forward it on to his current tower's location. This entire process takes less than 1 second to complete.

How Phones Are Verified and Calls Are Routed
As you leave the range of one tower and enter the range of a new tower your phone's ID information is transmitted to the closest cellular tower and verified as active through your carrier. Each tower then sends a message to your phone's "home station" which is typically found where your home station area code is located. When a call is made to your phone, the home station picks up the call and routes the call to the tower signal you are near. If you change towers while on the call, such as when traveling away from the current tower you are using, your phone will switch to the new tower. All of this occurs in less than one second, ensuring no disruption is service.

By James A Johnson