Fail-unlocked 39
The electric strike is locked for as long as the power is on. If the power is switched off or if there is a power cut, the keeper can be moved and the door can be opened.

Electric strike 39
Adjustable keeper (FF, FaFix®), Fail-unlocked

Electric strike 3905
Adjustable keeper (FF, FaFix®), Diode (05), Fail-unlocked