What is the difference between fail-safe and fail-secure (normally open and normally closed) for Access Control?
All electrified locking devices require either power to lock or power to unlock and fall into the category of fail-safe or fail-secure.
Fail-safe
A fail-safe lock such as a magnetic lock uses a normally closed (NC) circuit or a constant stream of power to remain locked. Fail-safe locks are commonly used in applications where it is deemed acceptable to allow entry and free exit to anyone during a power outage or emergency event. Before using a magnet lock, consult the local Fire Marshal or appropriate authority to ensure local code requirements are being adhered to.
Fail-safe locks should open or unlock allowing free exit during these common events:
- If triggered by a request-to-exit device
- If triggered to do so by a fire alarm system
- During a power outage
Fail-secure
Fail-secure locks (e.g., an electric strike) use a normally open (NO) circuit and do not require power to remain in a locked state. A fail-secure lock should open or unlock when the circuit is completed by the access controller in the event of a remote command or successful entry attempt. Typically, fail-secure configurations use hardware that allows those on the secure side of the door to exit freely.