GSM frequency bands or frequency ranges are the cellular frequencies designated by the ITU for the operation of GSM mobile phones and other mobile devices. Frequency bands GSM frequency usage around the world A dual-band 900/1800 device is required to be compatible with most networks apart from deployments in ITU Region 2. GSM-900, EGSM/EGSM-900 and GSM-1800 GSM-900 and GSM-1800 are used in most parts of the world (ITU-Regions 1 and 3): Africa, Europe, Middle East, Asia (apart from Japan and South Korea where GSM has never been introduced) and Oceania. In common GSM-900 is most widely used. Fewer operators use GSM-1800. Mobile Communication Services on Aircraft (MCA) uses GSM-1800. In some countries GSM-1800 is also referred to as "Digital Cellular System" (DCS). GSM-850 and GSM-1900 GSM-1900 and GSM-850 are used in most of North, South and Central America (ITU-Region 2). In North America, GSM operates on the primary mobile communication bands 850 MHz and 1900 MHz. In Canada, GSM-1900 is the primary band used in urban areas with 850 as a backup, and GSM-850 being the primary rural band. In the United States, regulatory requirements determine which area can use which band. The term Cellular is sometimes used to describe GSM services in the 850 MHz band, because the original analog cellular mobile communication system was allocated in this spectrum. Further GSM-850 is also sometimes called GSM-800 because this frequency range was known as the "800 MHz band" (for simplification) when it was first allocated for AMPS in the United States in 1983. In North America GSM-1900 is also referred to as Personal Communications Service (PCS) like any other cellular system operating on the "1900 MHz band". Frequency mixing between GSM 900/1800 and GSM 850/1900 Some countries in Central and South America have allocated spectrum in the 900 MHz and 1800 MHz bands for GSM in addition to the common GSM deployments at 850 MHz and 1900 MHz for ITU-Region 2 (Americas). The result therefore is a mixture of usage in the Americas that requires travelers to confirm that the devices they have are compatible with the bands of the network at their destination. Frequency compatibility problems can be avoided through the use of multi-band (tri-band or, especially, quad-band) device. The following countries are mixing GSM 900/1800 and GSM 850/1900 bands: GSM-450 Another less common GSM version is GSM-450. It uses the same band as, and can co-exist with, old