Abstract: A heat-triggered, mechanically-actuated apparatus comprising a heating and conducting linkage connected in parallel with an automatically resetting safety control switch across the power supply of electrical equipment, an initial opening of the control switch being indicated by the steps of heating of a heat-softenable rigid rod by the power supply passing through the heating and conducting linkage supported thereby, and breaking the linkage by a spring biasing the heat-softened rod to collapse and release a frictional connector in the linkage, and oppositely biasing an indicator, normally concealed a part of the linkage, into view.