TrueRH™ HT-670x Series Humidity Transmitters come in both wall or duct mount packages to meet a variety of sensing application needs. These attractively styled controllers offer ease of installation and application flexibility. Features TrueRH technology features patented improvements in circuitry and calibration techniques. All-Polymer humidity sensor provides accurate and reliable humidity sensing with the patented sensing element. tested and calibrated with equipment certified to be in compliance with National Institute of Standards and Technology (NIST) guidelines. jumper-selectable output: 0 to 10 VDC or 4 to 20 mA maximizes application flexibility. all-plastic material for duct probe improves thermal performance and complies with Underwriters Laboratories Inc. ® (UL) flammability ratings for plenum use.