Wireless programmable room thermostat designed and made by (Resideo) under the brand TotalHome as a direct replacement for the following Honeywell models:- CM727 CMS727 CMT727 CM921 CMS921 CM927 CMS927. The receiver can be paired to Honeywell BDR91 relay boxes that came with latter Honeywell models, they are generally square in shape rather than rectangular. An instruction video is available by scanning the QR code on the packaging. If needed, the relay box is simple to install and instructions are included. However professional installation is recommended. It must be installed at least 30cm away from the boiler to ensure maximum range. The receiver provides wireless communication with the relay box. It comes pre-bound so it will work without any pairing required. It offers 7 day programming and the ability to copy days to simplify the programming process. It has optimum stop/start and is boiler plus compliant which is part of Part L building regulations in to regards to new boiler installations. It will increase efficiency over a standard room thermostat and save energy and money on your bills. Programming is simple and intuitive. 7 days are individually programmable but you can easily copy a day to any of the other days of the week.