1G refers to the first generation of cellular network (wireless) technology. These are mobile telecommunications standards that were introduced in the 1980s and were superseded by 2G. The main difference between these two mobile cellular generations is that the audio transmissions of 1G networks were analog, while 2G networks were entirely digital. There were many different 1G cellular standards developed and used in different countries, but the most widely adopted globally were the Nordic Mobile Telephone (NMT) and Advanced Mobile Phone System (AMPS) systems. The inherent advantages of digital technology over that of analog meant that 2G networks went on to eventually completely replace them. Many 1G networks were switched off in developed economies by 2000, but in some places networks continued to operate into the 2010s. Overview The antecedent to 1G technology is the mobile radio telephone (i.e. "0G"), where portable phones would connect to a centralised operator. 1G refers to the very first generation of cellular networks. Cellular technology employ a network of cells throughout a geographical area using low-power radio transmitters. History The first commercial cellular network was launched in Japan by Nippon Telegraph and Telephone (NTT) in 1979, initially in the metropolitan area of Tokyo. The first phone that used this network was called TZ-801 built by Panasonic. Within five years, the NTT network had been expanded to cover the whole population of Japan and became the first nationwide 1G/cellular network. Before the network in Japan, Bell Laboratories built the first cellular network around Chicago in 1977 and trialled it in 1978. As in the pre-cellular era, the Nordic countries were among the pioneers in wireless technologies. These countries together designed the NMT standard which first launched in Sweden in 1981. NMT was the first mobile phone network to feature international roaming. In 1983, the first 1G cellular network launched in the United States, which was Chicago-based Ameritech using the Motorola DynaTAC mobile phone. In the early to mid 1990s, 1G was superseded by newer 2G (second generation) cellular technologies such as GSM and cdmaOne. Although 1G also used digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system, the voice itself during a call is encoded to digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150 MHz and up. Most 1G networks had been discontinued by the early 2000s. Some regions