Abstract: In order to control an external device 3, which may be associated with or remote from a terminal such as a mobile telephone 2, the terminal 2 sends a control request, for example in the form of an SMS message, to a telecommunications network 1. The network 1 converts the request into a control code which is in a form ready for controlling the external device 3. The control code is embedded in an SMS message which is then transmitted from the network 1 to the device 3, which has a GSM or other module associated with it in order to allow the embedded control code to be received, extracted, and supplied to the device 3 to perform the requested operation or function.