WJ-11 / RY51 / WJ-12 / RJ-12 are control units and I / O modules that serve as part of a building management system for the purpose of controlling heating, ventilation and air conditioning systems (HVAC). The reliable and robustly designed devices can be seamlessly locked together. In order to obtain the desired system control, the unit may be combined flexibly to improve the energy-saving performance of buildings. It is possible to set parameters and validate data through NFC on a smartphone.