说明：  《PLC、变频器和触摸屏实践教程》（第一、二章）。 高职院校实验（实训）系列教材。 书中选用西门子S7-200系列PLC，进行从基本指令到模拟量的处理，再到PLC与变频器的通信一系列项目的训练，目的是在帮助读者理解指令的同时，学会不同项目类型的编程设计方法，真正会用PLC。
(《PLC, frequency converter and touch-screen tutorial practice 》(first two chapters). Vocational test (training) series of textbooks. The book chosen Siemens S7-200 series PLC, the analog from the basic instructions to the processing, to the PLC and frequency converter series of training programs aimed at helping the reader understand the instructions at the same time, learn the different types of programming projects design method, to actually use the PLC.)