You guys are all awful.

The triggerzone has a special parameter called "onoff". If it is set to "on" (ID=1) it activates the trigger when touched (the animation goes from the first to the last tile). If it is set to "off" (ID=0) it does the opposite. The beforementioned animation goes back from the last to the first tile, IF it was activated before. Of course, if you turn a trigger out before it is activated, you're basically doing nothing.

So, a bit easier to understand:

1. On opens door
2. Off closes door again
3. Off does nothing if door wasn't opened before
4. On does nothing if door is already open

(of course you can do anything not restricted to doors, that was just an example)