Delta T Pro Lite Version 4.3.X firmware is for use ONLY with controls that have 3, 10K Ohm sensor inputs, not the 2 sensor input version. Loading incompatible firmware may cause a controller lockout and will void any warranty claims. The firmware software file has a .BIN extension. This file has been inserted into a folder then compressed into a .ZIP file for download below. Make sure to select the version applicable to the controller.