Dual-channel safety system (redundant chains)
A reliability block diagram of a 1-out-of-2 safety instrumented function — two independent sensor→logic→actuator channels in parallel, each a series chain. Shows how a parallel of series strings removes every single point of failure.
For the functional-safety engineer proving redundancy
What this shows
A 1-out-of-2 (1oo2) safety architecture: two complete sensor→logic→valve channels run in parallel, so the trip still fires if either channel works end-to-end. Each channel is itself a series chain — a channel needs all three of its elements.
Redundancy removes the single points of failure. Each channel alone has reliability 0.97·0.995·0.98 ≈ 0.946; in parallel the system reaches 1 − (1−0.946)² ≈ 0.997. Because no single block's failure drops the system to zero, the engine reports no single point of failure — the structural goal of a redundant safety function, proven by computation rather than asserted.