The Vulcan Hart 00-722248 Thermocouple uses the heat of the pilot flame to convert the heat into a small electrical signal of 20-30 millivolts to regulate the flow of gas in a safe manner. It measures the temperature variations at the burner and makes the gas valve open or close accordingly. The thermocouple is mounted close to the pilot assembly, and it reaches to the gas control sys... https://partsfe.com/thermocouple-for-vulcan-part-00-722248