Introduced to electrical power networks at the turn of the century, the use of power electronic devices to control and regulate single-phase networks has trailed behind. A likely reason for this outcome is the relative cost of ‘smart devices’ in a system of low earned revenue. Now a feature of grid modernisation projects, interest in ‘smart devices’ as a means to extend the useful life of distribution assets, delay capital expenditure, lower operating costs and to improve the supply reliability, is growing. Described in this paper for the control of single-phase transformers and reactors is a concept ‘smart switch’ that uses a low voltage low power thyristor. Built with a novel magnetic core and winding arrangement, the disconnection and reconnection of a transformer or reactor is controlled by the semiconductor switch. The concept design is demonstrated in this paper for a thermal overload and switched shunt reactor transformer applications.