Space identification system

System and method for identifying various types of room facilities to find out and take into account space information. A tag of a space (S2) is included in the fluctuation of the intensity of the light emitted by a lamp (LF1) provided in the space in question. The receivers included in the system are arranged e.g. in commercial mobile stations (R1). These are provided with a light detector and with a DSP algorithm that analyses the signal given by said light detector. As a result of the analysis, for instance the mobile station is automatically switched off when entering the space in question. There is neither needed a separate transmitter nor separate energy supply arrangements to send the space tag, and the space tag signal can be detected throughout said space. As regards the mobile station, the space-specific operations can be performed automatically, so that the mobile station user does not need to bother, and his possible negligence does not prevent the precautions from being executed.