analog NMT systems. NMT is a first generation (1G) mobile system which was primarily used in Nordic countries, Benelux, Alpine Countries, Eastern Europe and Russia prior to the introduction of GSM. The GSM Association claims one of its around 680 operator-members has a license to operate a GSM 450 network in Tanzania. However, currently all active public operators in Tanzania use GSM 900/1800 MHz. There are no publicly advertised handsets for GSM-450 available. Very few NMT-450 networks remain in operation. Overall, where the 450 MHz NMT band has been licensed, the original analogue network has been closed, and sometimes replaced by CDMA. Some of the CDMA networks have since upgraded from CDMA to LTE (LTE band 31). Multi-band and multi-mode phones Today, most telephones support multiple bands as used in different countries to facilitate roaming. These are typically referred to as multi-band phones. Dual-band phones can cover GSM networks in pairs such as 900 and 1800 MHz frequencies (Europe, Asia, Australia and Brazil) or 850 and 1900 (North America and Brazil). European tri-band phones typically cover the 900, 1800 and 1900 bands giving good coverage in Europe and allowing limited use in North America, while North American tri-band phones utilize 850, 1800 and 1900 for widespread North American service but limited worldwide use. A new addition has been the quad-band phone, also known as a World Phone, supporting at least all four major GSM bands, allowing for global use (excluding non-GSM countries such as Japan, South Korea and as well countries where 2G system was shut down to release frequencies and spectrum for LTE networks like Australia (since 2017), Singapore and Taiwan (since 2018). There are also multi-mode phones which can operate on GSM as well as on other mobile phone systems using other technical standards or proprietary technologies. Often these phones use multiple frequency bands as well. For example, one version of the Nokia 6340i GAIT phone sold in North America can operate on GSM-1900, GSM-850 and legacy TDMA-1900, TDMA-800, and AMPS-800, making it both multi-mode and multi-band. As a more recent example the Apple iPhone 5 and iPhone 4S support quad-band GSM at 850/900/1800/1900 MHz, quad-band UMTS/HSDPA/HSUPA at 850/900/1900/2100 MHz, and dual-band CDMA EV-DO Rev. An at 800/1900 MHz, for a total of 'six' different frequencies (though at most four in a single mode). This allows the same handset to be sold for AT&T Mobility, Verizon, and Sprint