继电—接触式控制系统因其控制线路复杂,安装工作量大,触点容易损坏,改变控制功能和维修困难等原因,正逐渐被功能强大,可靠性高,简单易学,操作方便的PLC所替代。 Relay - contact control system because of its complex control circuit, the installation of large workload, contacts easily damaged, changing control functions and maintenance difficulties and other reasons, is gradually being powerful, high reliability, easy to learn, easy to operate PLC Alternative.