a lock that unlocks at the wrong time has failed

dec-sev

Senior Member
Russian
Hallo.

"For example, a lock that unlocks at the wrong time has failed, but it may be considered fail-safe if its failure does not send the door flying open or attract undue attention to the door's unlocked state. In contrast, a fail-secure lock will remain locked during a failure, but cannot be unlocked even by the correct key."

It's from here. I don’t understand the underlined part. What does “has failed” refers to? The phrase seems to be so structured that unlocking of the lock at the wrong time is its normal operating condition and “has failed” refers to the fact that the lock has failed to unlock at the wrong time. But that makes no sense. What do you think?
 
  • Thomas Tompion

    Senior Member
    English - England
    I agree that it's badly put, Dec-sev, but think that the example makes the meaning clear.

    The idea seems to be this: you have an automatic lock which is set to unlock at a particular time. If it fails, it unlocks at the wrong time - failure here means a failure of the timing mechanism, not of the lock's power to keep the door, or whatever, secure.

    The question is - what happens when the timing mechanism fails? In a fail-safe system the door stays shut, so the failure isn't obvious, but people can open the door. In a fail-secure system, the door stays shut, and cannot be opened, even by people with the key.
     

    b1947420

    Senior Member
    British English
    Hallo.

    "For example, a lock that unlocks at the wrong time has failed, but it may be considered fail-safe if its failure does not send the door flying open or attract undue attention to the door's unlocked state. In contrast, a fail-secure lock will remain locked during a failure, but cannot be unlocked even by the correct key."

    It's from here. I don’t understand the underlined part. What does “has failed” refers to? The phrase seems to be so structured that unlocking of the lock at the wrong time is its normal operating condition and “has failed” refers to the fact that the lock has failed to unlock at the wrong time. But that makes no sense. What do you think?
    It seems to me that there are two things to consider.
    1) The time-lock feature.
    2) The fail-safe feature.

    If the lock becomes unlocked at the wrong time then the time-lock feature could be considered to have failed.

    This time-lock feature however has failed in such a way as to safeguard the security aspect. The issue of not being able to open the lock under these circumstances is a lock design matter.

    Note: Posted without knowledge of Thomas's post.
     
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