Abstract: A system uses a mobile unit to control access to physical spaces with electrical locking devices. An authority means connected to the mobile unit issues authorizing data (AD) access rights, which are sent to an authorization means connected to the authority means, generate a mobile unit alpha-numerical key and send the key and the mobile unit's unique identifier to an operator connected to the authorization means. The operator sends the alpha-numerical key to the mobile unit identified by the unique identifier. An electrical locking device and the mobile unit use an authentication protocol with the alpha-numerical key to authenticate the mobile unit, which, when authenticated, sends the authorizing data (AD) to the electrical locking device. If the authorizing data (AD) comprises an identifier of the electrical locking device, the mobile unit can open the electrical locking device using a communication means in the mobile unit for near field communication.