Description
输入设备占45%，输出设备占30%，线路占5%。前二项共20%故障属于PLC的内部故障，它可通过PLC本身的软、硬件实现检测、处理；而其余80%的故障属于PLC的外部故障。因此，PLC生产厂家都致力于研制、发展用于检测外部故障的专用智能模块，进一步提高系统的可靠性。
ALLEN BRADLEY MSR138DP GUARDMASTER SAFETY RELAY *NIB*
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Allen-Bradley GuardMaster 440R-B23020 SAFETY RELAY NNB
Allen-Bradley Guardmaster MSR Dual Channel Safety Relay
Allen Bradley Safety Relay Guardmaster 440R-ZBE820AZ1
