SECURITY SYSTEMS

In a security system in which home control units communicate with a remote operations centre to receive coded information characterising release signal s for security aware apparatus, the home control unit is responsive to signals from global positioning satellite system (GPS signals) to determine its location. The locational data may then be transmitted to the remote operatio ns centre by direct radio communication (45), by communication by way of low earth orbital satellites (49), by communication through a GSM cellular switching centre (51) or by way of connectionless communication using the internet (52) or electronic mail messaging systems.