What you need to know:

The most popular frequencies worldwide are GSM: 850, 900, 1800 and 1900 MHz. The US operates on two GSM bands: 850 MHz and 1900 MHz. On the other hand, Europe, the Middle East and Asia operate on 900 MHz and 1800 MHz.

Each cell phone performs on specific bands. It is important to know which bands your phone is compatible with, if you are planning to travel overseas with a single handset.

Dual-band phones released in the US will be useless in Europe or Asia due to network differences.

Tri-band and quad-band phones run on a combination of three and four bands which guarantee you that your phone will have service throughout the world.