What is GSM?
Short for Global System for Mobile Communications, one of the leading digital cellular systems. GSM uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency.
GSM was first introduced in 1991 and is now the most popular standard for mobile phones in the world. GSM phones are used by over a billion people across more than 200 countries.
GSM networks operate at various different radio frequencies. Most GSM networks operate at 900MHz and/or 1800MHz. The exception to the rule are networks in parts of the Americas (including the USA and Canada) that operate at 850MHz and/or 1900MHz. Many GSM phones provide coverage in countries other than the USA. Cingular and T-Mobile use GSM.
If you are traveling overseas and have decided to buy a GSM phone, there are a couple of things you need to know. Cellular services all over the world require you to pay to talk. Generally speaking, this means subscribing to an international GSM service.
Optionally you can buy and install a GSM service supplier’s prepaid or post-paid SIM in your cell phone. These can usually be found in international airports. In order for your new, international SIM to work, your cell phone must be “unlocked.” Many tri-band phones today come unlocked out of the box, such as the recommended Motorola RAZR V3 Black Phone (Unlocked). If your phone is “locked,” you’ll need to have your supplier or a third party unlock it using special software.