The device (No Key hardware unit) is directly connected to the electronic lock of the building (same as intercom) and it conducts unlocking process. The ability to unlock using the key intercom is not disturbed. During all usage options safety is ensured with unique code for a specific lock and special code for each resident of the building (at the moment of approach to the building, in the case that Bluetooth on the mobile telephone is turned on and if an automatic unlocking application is set ) The device operates in four ways: 1. Automatically, without user’s activity. The entrance door unlocking is completely autonomously, through pairing mobile telephone app and the lock. Upon the approach to the entrance door of the building, the lock and the telephone are paired through the Bluetooth device and the app sends the signal to the lock which unlocks itself upon the receipt of the signal. The resident of the building has interaction neither with mobile telephone nor with the lock before it unlocks. Upon the approach to the entrance door, it unlocks itself. 2. Clicking a phone app. through Bluetooth connection (app) of the mobile telephone and the lock. Upon the approach to the entrance door, the user by clicking mobile telephone sets Bluetooth on, the app is paired with the lock and it sends a request for the door to unlock, subsequently, the door is opened automatically. 3. Through internet connection of the mobile telephone and the electronic lock that is connected to the internet. Residents of the building are able to open the door of the building from any distant place. It is necessary for telephone to be connected to the internet and with a single click to the app on their phone they are able to open the door of the building where they reside (in the case when the lock is not in the range of the Bluetooth of the resident). 4. Through a Bluetooth pendant which, upon the approach to a certain distance from the door of the building, automatically connects and sends a signal to the device to unlock the building.