It has three positions: Normal, Unlock, and Lock.
To unlock the door, a pilot moves the switch to Unlock. In an emergency, the cabin crew can enter a secret code (easily extracted by any competent jihadi), which causes the door to unlock. However, if the pilots suspect trouble, they can move the switch to Lock. That disables the unlock code for the next five minutes to twenty minutes (programmable). The unlock code sounds an alarm first, reminding the pilots to renew their veto on entry. Of course, if they are incapacitated, that won't happen, and the door will unlock.
A training video is the top Google search result.
is it even possible that after the pilot opened the door to exit the cockpit, one of the passengers forced himself in and locked the door to take down that plane? Maybe the breathing wasn’t from the co-pilot, but from that someone else?
Thanks, I’m aware of the functions thanks to other posters.
What I meant was, where is it located, how is it set, etc. Concierge engineering and the like, or not.
This all plays into how easy it is - or is not - to use, especially while seated in either seat.
It is a frequent subject in accident investigation - where are XXXX and could the person get it, or make a mistake hitting it, etc.