An access control system will constitute four key elements; a tag, reader, controller and lock. Each user will have a tag, such as a card or a smartphone, which will be authorised on specific doors at specific times by an administrator. These credentials will then be read by the reader. Should the tag be authorised at that time, on that door, and presented near to the reader, the door will unlock. The controller is then the core of the system, which will store all of the information about who is authorised and when which is controlled by a central computer. Finally, the lock is an electro-mechanical locking device.