Abstract: A security system for not enabling, enabling or disabling electrical devices for deterring theft, or preventing unauthorized use of such devices. The security system comprises a plurality of electrical devices which are operationally linked via a bi-directional communication medium, which may be via a mains power supply or a microwave or radiowave medium. Programmable means are provided for controlling operation of the operative parts of the electrical devices. The programmable means may have a signal transmitting and receiving means associated with it for transmitting and receiving control signals over the communication medium.