3U时隙交叉设备原理图，PCB。漫游短信欢迎系统(信令采集设备部分)培训资料-Schematic cross-slot 3U equipment, PCB. Welcome to SMS roaming system (part of the signaling equipment acquisition) training materials

国内电信行业应用的数据库模型-三户模型 培训讲义-The application of the domestic telecommunications industry database model- three model training handouts