可编程序控制器原理及应用的备课笔记的第一部分，对学习PLC的朋友来说会有很大的帮助。 -Programmable logic controller and application of the principle of the first part of lesson notes on learning PLC' s friends will be of great help.

2004年全国PLC技能大赛试题解答-计数器法解答-2004 National Skills Competition PLC questions to answer- to answer the counter method

powerline carrier (PLC) is a way to tarnsfer data from telphone line, no need to power or backup battery.