I had assumed that these two failure modes covered the full extent of the ways in which an electronic door lock could plausibly fail. Foolish me. This afternoon the speakers which make the locks go beep on unlocking have jammed on, so that all the locks in the building are emitting a continuous high-pitched whining noise.

ROFL. Doh!

Question: Trapped in? Are the doors not openable outwards with buttons, or did that fail also?

way of letting people like me know that they haven't nearly exhausted their options yet;

Indeed. It reminds me of trying to write about a demon-summoning from the demon's point of view. Despite having almost no power except where specifically granted, it eventually bends everyone to its will.

Each door has an infra-red sensor on the inside, and a pass-card reader on the outside. They're supposed to unlock when anyone walks up to them trying to get out, or when anyone waves a valid card at them wanting to get in.

The failure was apparently in the lock rather than the card reader, so they failed to unlock in either case.

(The IR sensors are good for a laugh at the end of the working day, too. Whenever I put my big black coat on, they suddenly have only a 50% chance of noticing me, presumably because the coat has been hanging on a hook all day and hence is at room temperature rather than body temperature.)

Ah, I see. That is unfortunate. I hope there were working fire doors just in case?

The IR sensors are good for a laugh at the end of the working day, too.

Stealth Simon! You've been watching too much Predator, except you're an ARM and free software designer rather than the ultimate military killing machine.

There's a fire door in the room I work in, but I don't think every room has one. So some people must have been genuinely trapped.

I've never actually seen Predator, although I think I sat in front of at least part of Predator 2 at one point without paying much attention. I assume the Predator does some similar sort of thing?

You could probably chuck a monitor through the window if you were really stuck.

That might be less fun for the people on the first floor, but yes, there would have been a variety of ways out given enough motivation. I didn't really mean "trapped" in the sense of "really actually likely to starve to death in there if the locks don't start working again", more in the sense of "unable to get out without causing somebody a serious inconvenience, no matter who it turns out to be".

I assume the Predator does some similar sort of thing?

Yes, though the antecedants may be confused. The IR door lock represents the alien, the predator, who has heat vision. You represent Arnie. The coat represents implausibly high heat capacity river mud. All that's necessary is for you to smash the lock with your bare hands and it'd be perfect; you can't say you're not tempted.

It would, of course, be vastly more amusing (in a glad-I'm-a-long-way-away kind of way) if, for the sake of accuracy, the door also featured a thermonuclear self-destruct system keyed to activate in the unlikely event that anyone succeeded in escaping from the building.

I don't think every room has one. So some people must have been genuinely trapped.

This is legal where you live?

Allowing for the possibility of trapping someone in case of a fire seems rather dodgy to me.

Hmm… I wonder if that works on security alarm motion sensors, too…

Of course, it's when the doors start saying "glad to be of service" that you have to start worrying in earnest.

My central locking spends several days not working at all, and then if I open the driver's window it goes ka-chunk-ka-chunk-ka-chunk in all the doors simultaneously (except the driver's which currently has no lock...) as it catches up. Innovative things, locks.

You want to do whoever designed those doors under Health and Safety, now rather than after lots of people die in a fire. They need an inside mechanical manual override.

I’d worry if they started following me down the corridor.

If unlocking door n unlocks doors f(n), how do you unlock door 1...? Also, see 13 ghosts.

At Nottingham in the new building, we had a fun fire drill. We accidentally overheatd a sub-station turning the server room on which a) set of the fire alarm and b) disconnected the power. This caused the locks to go into one of two states depending on their failsafe state and whether they could be used in a fire. (Ideally the locks would be arranged so that "fire" and "no power" were similar). Unfortunately, someone had installed the lock-on-power and lock-on-no-power electromagnets semirandomly, and configured the attached control box to do the right thing for that (randomly selected) bolt in normal conditions. This meant that when the power failed the doors altered configuration in two ways. Of course we didn't know the new building too well and there were no lights. Oh, and no windows in the firedoors apart from slits seven foot off the ground. Also some doors were stealth doors. Normally these were disguised as walls (being just slabs) but swung into the corridor in the case of a fire and locked (they should have closed, but shouldn't have locked). So we were in a building we dind't know, in the dark, and it had changed topology in unpredictable ways. And we had to get out. Sometimes they're just out to get you, :).

That sounds more like an unlikely computer-game scenario than a real fire drill! I'm impressed. :-)

The amusing thing is it happened about an hour after The Queen and Prince Philip had left after the official opening. It was more like one of those odd stress dreams.

A $nationality firedril perhaps.

Thing I'd do if I ever became an evil overlord (http://www.eviloverlord.com/lists/overlord.html) #96: My door mechanisms will be designed so that blasting the control panel on the outside seals the door and blasting the control panel on the inside opens the door, not vice versa.

Well, depends on your threat model really. If that's the door to a prison cell into which you think there's any possibility of throwing a hero who you have inadequately frisked for weapons, it's entirely back to front...

Bah! I am the overlord, "inside" is whichever side *I'm* on, damnit! :)