ABB DSSR122 4899001-NK是冗余模块，主要功能是在非SIL和SIL1-2操作期间提供控制器的智能监控，并与PM865一起形成适用于SIL3应用的1oo2多样化结构。它含有专用的同步链路以同步活动和冗余的SM，还有热插入和在线升级功能，能在冗余设置中的两个SM811之间复制数据。

It is a redundant module with the main function of providing intelligent monitoring of the controller during non SIL and SIL1-2 operations, and together with PM865, it forms a 1oo2 diversified structure suitable for SIL3 applications. It contains dedicated synchronization links to synchronize active and redundant SMs, as well as hot insertion and online upgrade functions, which can replicate data between two SM811 in redundancy settings.