A mobile communications device control system is provided. The system is for use with a device capable of receiving and transmitting data in the form of calls or messages. The device is provided with receiving means for receiving a signal from a location (2), processing the signal and altering the operating condition of the device in accordance with the received signal. The signal emitted from the location (2) is effective within a localised, determinable area (8) of the location, thereby providing a localised controlling effect on the operation of the device.