Adjustable thermal switch is the simplest thermal switch which must be mounted near the heat source. The fan will turn on when the temperature at the switch reaches the temperature the knob is set to and turns off when the temperature is 10 degrees lower. It can be set to turn the fan on between 80 and 130 degrees. To install simply plug the thermal switch accessory into an always-live source of 120Vac power and plug the system 1's fan into the female end of the thermal switch's power cord. Place the thermal switch assembly where it can sense the heat generated by the equipment in the enclosure. Set the adjustable switch's knob to the desired turn-on temperature. There is a fixed 10 degrees temperature differential, the fan will turn off about 10 degrees below the temperature at which it turns on. Hair dryer can be used to test the thermal switch for proper operation. The face plate of the switch is the temperature-sensitive element.