What is the network signal of mobile phone?

GSM900 and DCS 1800 are what we usually call dual-band networks. Both are GSM standards. The two systems have the same function, mainly with different frequencies. GSM900 works at 900MHZ and DCS 1800 works at 1800MHZ. GSM900 was first used in China. With the rapid development of communication network scale and the number of users, the frequency of the original GSM900 network has become increasingly tense. In order to better meet the growing needs of users, China recently introduced DCS 1800, and adopted the networking mode of GSM900 network as the main network, supplemented by DCS 1800 network, forming GSM 900/DCS 1800. Users can switch freely between GSM 900/DCS 1800 and automatically select the best channel to make a call by using dual-band mobile phones. Even during the call, the mobile phone can automatically switch between the two networks without the user's notice, and the mobile phone chooses the best channel, which improves the connection rate. In order to adapt to this trend and further seize the market share, Nokia, Motorola, Ericsson and other world-renowned mobile phone equipment manufacturers compete to develop and launch multi-band mobile phones.