How an Access-Controlled Door Works

Every access-controlled door is made of the same few parts. Tap each one to see what it does, and what happens when the fire alarm sounds or the power goes off.

1. 1.Reader: Checks the fob, card, phone or PIN, and asks the controller whether this person may open this door now.
2. 2.Controller: Decides who can go where and when, and keeps a log of every door event, so you can see who opened which door.
3. 3.Lock: A magnetic lock or electric strike holds the door shut until a valid credential, exit button or fire alarm releases it.
4. 4.Exit button: Lets people out from the inside without a credential.
5. 5.Green break-glass: Cuts power to the lock in an emergency so the door can be opened at once.
6. 6.Door contact: Tells the system if the door is forced open or left open too long.
7. 7.Power supply and battery: Powers the lock and reader, with a battery to keep the door working for a time if the mains fails.
8. 8.Fire alarm link: Releases the door automatically when the fire alarm sounds, so nobody is trapped on an escape route.

Fail safe (fail unlocked)

Unlocks when the power fails or the fire alarm sounds.

Used for: Escape routes and fire exits

Fail secure (fail locked)

Stays locked when the power fails, with a mechanical key override.

Used for: Store rooms and cash offices, never an escape route

Fob or card

Best for

Most staff doors

Watch out for

Can be lent or lost, so remove leavers promptly

Phone

Best for

Staff who always carry a phone, and remote sites

Watch out for

Needs the app set up on each phone

PIN

Best for

Adding a second check to a fob

Watch out for

Codes get shared if used on their own

Biometric

Best for

High-security rooms

Watch out for

Higher cost, and personal data rules apply

Answers come only from our standards library and quote their sources. They are general guidance, not advice for a specific building, and are produced automatically, so check the source before relying on them. Please don't include names or personal details in your question.

What happens to the doors in a fire or a power cut?

Fobs, cards, PINs, phones or biometrics?

What is the difference between Net2 and Paxton10?

How often should access control be maintained?