A fail-safe backup system ensures reliable operation, even if a fault develops in the main circuit.

一个自动防故障装置的后备系统确保了可靠的运转，即时在主要电路产生了故障。

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The backup saved the day -- just as it did in July 1999 when a short circuit knocked out some engine controllers six seconds after Columbia lurched off the pad.

CNN: Challenger explosion

Circuit boards are double-insulated to protect against power surges, and there are backup power supplies that can be switched out on the fly.

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