A Global System for Mobile (GSM) antenna is a type of antenna commonly used in mobile phones and cell towers. Global System for Mobile Communications is the most common type of cellular network worldwide. The antenna in a GSM phone allows the device to communicate with another GSM antenna on a cell tower, which then relays the signal to another tower or to another cell phone. GSM service can be used on a number of radio frequencies, depending on the region and technology used. Many modern phones with GSM antennas support a variety of these frequencies so that they can be used while traveling.
Most modern mobile phones have an internal GSM antenna, usually contained in or near the bottom of the phone. Some older phones have an external pull-out antenna or a small bump of an antenna on the top of the phone. Both internal and external GSM antennas work in the same way.