The TQ transmitters are used in air conditioning system for the detection of air quality (presence of human perspiration products, cooking vapors and tobacco smoke, etc.).Do not use for safety applications. In particular, the TQ-A31 model is intended for installation in the environment while the TQ- D31 model in the air duct. The TQ transmitters detect the air quality through a semiconductor sensitive element whose signal, appropriately linearized and amplified, is transformed into a voltage signal (0..10 Vcc ).