China Double SIMs mobile phones In order to alleviate existing mobile phone system capacity, insufficient contradiction, in addition to develop new frequency band in the 800M GSM (e. g. , develop 900M frequency, also take on) the development of new system based on frequency (such as CDMA system). Dual mode mobile phone is compatible with two different kinds of mobile phone system of mobile phones. It is the basic structure in the central control unit under the control of the man-machine interface, by using the same antenna is coupled to the two independent system. In the mobile phone use, the central control unit testing and between the two systems.