The Lang 80504-03 thermocouple detects pilot flame heat and produces a small electrical signal measured in millivolts. This signal supports the gas control system's flame-sensing process in compatible 1980 Series commercial equipment. With a 60-inch length and a 20–30 mV rating, the assembly provides the specified reach and output range for its intended installation. https://partsfe.com/thermocouple-80504-03/1-80504-03.html