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::''This article is about mobile phone standards. '1G' is also the IATA code for Galileo International.''
'1G' (or 1-G) is short for first-generation wireless telephone technology, cellphones. These are the 'analog' cellphone standards that were introduced in the 1980s and continued until being replaced by 2G 'digital' cellphones. The main difference between two succeeding mobile telephone systems, 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G networks are digital.
Although both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system, the call itself is encoded to digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150MHz and up.
One such standard is NMT (Nordic Mobile Telephone), used in Nordic countries, Switzerland, Netherlands, Eastern Europe and Russia. Others include AMPS (Advanced Mobile Phone System) used in the United States, TACS (Total Access Communications System) in the United Kingdom, C-450 in West Germany, Portugal and South Africa, Radiocom 2000 in France, and RTMI in Italy. In Japan there were multiple systems. Three standards, TZ-801, TZ-802, and TZ-803 were developed by NTT, while a competing system operated by DDI used the JTACS (Japan Total Access Communications System) standard.
Antecedent to 1G technology is the mobile radio telephone, or 0G.