Description
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 Safety Relay Guardmaster 440R-ZBR520AZ1
Relay Safety Guardmaster AB catalog# 440R C23017 ser A
AB Guardmaster Safety Relay 440R-ZBR520AZ1 440RZBR520AZ
Allen Bradley Guardmaster Safety Relay 440R-ZBR520AZ1
USED Allen Bradley 440R-N23132 Guardmaster Safety Relay
