Abstract: A protective circuit for protecting electrical equipment. The circuit has a eat sensor for sensing heat from the electrical equipment, an amplifier for amplifying the sensor voltage. The circuit also has a power supply, a heater, and drive transistor for conducting current from the power supply to the heater due to amplified sensor voltage on the drive transistor. The circuit further has a heat sensitive switch that has a switching temperature. The heat sensitive switch is between another power supply, for the electrical equipment, and the electrical equipment. The heat sensitive switch initially conducts electrical power to the electrical equipment. The switch will interrupt electrical power to the electrical equipment, after a selected rate of heat from the electrical equipment activates the circuit to cause the heater to produce a switching heat. This switching heat from the heater raises the temperature of the heat sensitive switch above its switching temperature.