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Safety Relay Topic: Reason of Two Inputs are Required

FAQ No. FAQ02378

Question

Why are two inputs required for the Safety Relay Unit?

Answer

Safety categories 3 and 4 under EN 954-1 require that safety functions are not lost if one part malfunctions.

That is why two inputs are required.

Other Safety Relay FAQs

 What is the difference between Safety Relays and Safety Relay Units?

 What is a positive common input?

 What is the difference between a Safety Relay and a General-purpose Relay?