Master key system: how does it work?
A master key system, also known as a key plan or master key scheme, determines which key opens which doors. Each employee carries one key; the person in charge carries a master key. This is how it works.
Three types of keys
In a master key system, the doors are in rows and the keys in columns. An individual key opens one or a few doors: an office, a storeroom. A group key opens all doors of a department or unit, for example the technical rooms. A master key opens everything included in the plan.
Because each cylinder must accept multiple keys without the wrong key fitting, the plan is calculated in advance. That is precisely why a master key system can be extended without replacing existing cylinders, provided room for this was allowed for in the design.
What is included?
Not just door cylinders. Padlocks for gates and storage, thumbturn cylinders, half cylinders for technical cabinets, furniture locks and even a container lock can all use the same key. An employee no longer needs to carry a bunch of keys.
Exclusive profile and key card
A patented system such as Mul-T-Lock MTL 400 or MTL 800 comes with a key card. Additional keys are duplicated only on presentation of that card and after verification of authorisation. If the supplier also works with an exclusive key profile, keys and cylinders stay within a single channel. That is the essence of copy protection: not the lock, but the procedure around the key.
What if a key is lost?
A mechanical key cannot be blocked remotely. If one is lost, you check which doors it opens; to be certain, you replace all those cylinders. With an electronic system, the key is deprogrammed. A good plan limits the impact: an individual key affects one door, a master key the whole building. That is why master keys are best kept in an electronic key cabinet with logging.
Mechanical and electronic together
A master key system determines who can open which door. Electronic key management determines who receives the key and records when it is returned. Together they form a complete chain: fewer keys in circulation thanks to the plan, and visibility of the keys that do circulate thanks to the cabinet.
See also: Mechanical locking systems · MTL 800 · Key duplication
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