西门子MM440变频器上位机控制界面，可执行启动，加减速，正反转及停止等功能-Siemens MM440 inverter PC control interface, the executable to start, acceleration and deceleration, reversing and stop functions

利用模块实现继电器的开与闭，从而进行必要的电机正反转控制-Use of modules realize relay on and off