The Resideo Q313A1139 is a Thermopile Generator a vital part of HVAC systems, which is used in converting thermal energy into electrical energy. This device has a length of 35 inches and an output voltage of 750 mV. It uses thermocouples to change the heat that is generated by a pilot flame or any other means into electrical energy. This electricity can then be used to power gas valve... https://www.partshnc.com/q313a1139-resideo-750mv-thermopile-gen35-lead