[publius911]

It is fail safe, in that if power fails in an emergency, the door unlocks automatically.

I sure hope that's true only after the plane is on the ground!

[chaosagent]

The electric lock is in addition to the standard manual locking mechanism that usually locks the door. The electric lock keeps someone from opening the door manually while the plane is taxiing, or flying under 8-10,000 feet when the pressure differential no longer keeps the door from being opened at all.