说明：  常用modemAT指令详解，对常用的AT指令进行了较详细的介绍并适当进行了扩充目的是使工程师在调试过程中能收集一些有用的信息以便对问题进行定位。
(common modemAT instructions Hi, on the AT command used for a more detailed account of the proper conduct and the purpose of the expansion is to enable engineers to the debugging process can achieve Set some useful information in order to locate the problem.)