What access control systems actually do, and when a business needs one
Keys have one flaw you cannot engineer around: you can't tell who has a copy. Here's what replaces them, and the point at which it becomes worth doing.
A mechanical key has one weakness that no lock design fixes: you cannot tell how many copies exist. Every departing employee, every contractor who held a key for a week, every tenant who moved out — each is an unknown. The only honest response to a lost key is to rekey the cylinder, and that cost repeats every time.
Access control replaces the physical key with a credential you issue and revoke centrally. When someone leaves, their access ends that afternoon, whether or not you ever get anything back from them.
The three parts of any system
Regardless of manufacturer, every installation is the same three things:
- A credential — the card, fob, PIN, fingerprint, or phone that identifies a person.
- A reader — the device on the wall that reads it, wired back to a controller.
- A controller — the box, usually in a closet, that decides whether the door opens and records that it happened.
The controller is the part that matters and the part nobody looks at. It holds the permissions and the audit log, and it is what determines whether the system still works when the internet is down. Ask about that specifically: a controller that fails open is a security problem, and one that fails locked can be a life-safety problem.
Credential types, honestly compared
- Keypad / PIN — cheapest, no credential to issue. But codes get shared, and a shared code destroys the audit trail because every entry looks identical.
- Card or fob — the common commercial default. Easy to issue and revoke. Older 125kHz proximity cards can be cloned with hardware costing under fifty dollars; modern encrypted formats cannot.
- Mobile credential — the phone becomes the credential. Nothing to hand out, nothing to collect, and people notice a lost phone far faster than a lost fob.
- Biometric — fingerprint or face. No credential to share or lose, which makes the audit log genuinely trustworthy. Slower per entry and unpopular at high-traffic doors.
When it becomes worth doing
There is a reasonably clear threshold. Access control pays for itself when any of these are true:
- Staff turnover means you are rekeying, or quietly deciding not to bother.
- Different people need access to different areas — a stockroom, a server closet, a records room.
- You need to know who entered and when, whether for an incident, an insurer, or a compliance requirement.
- You have more than one site and are managing each one separately.
- Doors need to lock and unlock on a schedule rather than by someone remembering.
Below that threshold — a single door, three people, no turnover — good locks are a reasonable answer and anyone telling you otherwise is selling.
The part that gets skipped
Access control touches life safety. Doors on an egress path must release when the fire alarm sounds, and that interface is inspected. A system installed without it can fail inspection, and in the worst case can trap people. This is exactly why New York licenses this work.
Ask any contractor for their licence number before they touch a door on an egress route. Including us.