Central lock systems

Central lock systems are used in houses shared by several apartments. Central doors such as the front door, veloroom, underground garage, cellar entrance need to be able to be locked by every inhabitant of the house with their apartment key. No single apartment key should fit the lock to another apartment, however. Central lock systems can be upgraded to include letterboxes, the cellar, or storage boxes in the common garage area on the apartment key, giving only access to the authorised persons. Every tenant carries only a single key with them for the property they inhabit; the building manager doesn't need to obtain, issue, and keep track of individual keys for common doors.