The central key system is a system, where several different individual keys operate one or several central cylinders.
Each tenant of an apartment building can open with his apartment key the main door, cellar, bike room or attic.
The central key system with a technical master key is a system where an additional key - the technical master key - is operating several different central cylinders.
Each tenant of an apartment building can open with his apartment key the main door, cellar, bike room or attic. Furthermore, there is a technical master key as access for service technicians or for the postman in case of interior mail boxes
The master key system is a locking system where one master key is operating all existent cylinders of the locking system.
The CEO of a company can operate with a master key all rooms of his company. All other keys just open the entrance door and several doors to the offices / work places.
A grand master key system is a locking system that combines two or more master key systems together. In this case, the master keys are called group keys and the key that is able to operate all cylinders of the locking system is called grand master key.
Various functional areas of the locking system can be divided into groups (e.g. administration, engineering, etc.). The respective heads of department can only operate the cylinder of their group; individual employees can operate the main entrance and the entrances to their offices or departments of their working areas within the group / department.