The UTY-TTRXZ1 is a thermostat converter for Fujitsu high-efficiency Halcyon mini-split and Airstage variable refrigerant (VRF) heating and cooling systems which allows the Fujitsu system to be controlled by a third-party thermostat. By installing the converter between the third-party thermostat and Fujitsu system, control of the heating and cooling system is provided, including on/off control, operation mode, room temperature, fan speed, and error notifications via LED lights. Tested with Honeywell, Nest, and other thermostats.