The grand master keyed system is a system where two or more master keyed systems are combined. In this case the master key is called group key and the key that can operate all cylinders of the system is called grand master key.


Example:
Various areas of the system are divided into groups (e.g. administration, technical department, etc.). The respective manager of the department can only operate the cylinders of his group. The owner of the grand master key has access to all rooms of the system.