An actuator is provided having a temperature activatable actuating member comprising an inductively couplable material. The actuator has an electrical heating element for electrically heating the actuating member. The heating element is configured to inductively couple with said material when an AC current is passed through the heating element such that an opposing electromotive force is induced in the heating element. A detector is provided for detecting activation of the actuating member by sensing a change in the AC impedance of the heating element.
