【简答题】观察全局DB块的数据特点,它与FB的背景数据块有何区别?
【简答题】setback: n. a problem that delays or prs progress, or makes things worse than they were 挫折,阻碍 Examples: The team suffered a major(1) when their best player was injured. He has suffered a serious ...
【简答题】三极管是____控制性器件,是指输入电流对输出电流的控制作用。
【判断题】( )用试灯检查电枢绕组对地短路故障时,因试验所用为交流电源,若必须采用高电压时,应采用隔离变压器,并且要特别注意安全。