fail-safe

剑桥词典

very unlikely to fail
万无一失的，万全的
a fail-safe plan 万无一失的计划

If something is fail-safe, it has been designed so that if one part of it does not work , the whole thing does not become dangerous .
可自动防止故障危害的；有自动保险装置的
a fail-safe device 故障保护装置 返回 fail-safe