Non-Fail Safe and Fail Secure Electric Door Strike
A fail safe electric strike needs power to keep it locked. A fail secure electric strike stays locked even without power. The most common by far is a fail secure. When using a fail secure electric strike even without power it stays locked from the outside coming in. For egress or getting out, a door knob or lever on the lock allows for safe exit. If you must use a fail safe electric strike don't forget to back it up.