Temperature sensor, 20,000-ohm Negative Temperature Co-efficient (NTC), duct mounted. Direct-wired temperature sensor used to sense discharge or return air temperature in duct controlled by Excel 10 Series 2000 controller. Rugged aluminum, six-inch insertion probe. Operating temperature range: 45-99F. For use with W7751 electronic control systems, primary and/or secondary sensor. Integral 20K-ohm non-linear NTC thermistor. Rugged aluminum insertion probe.