This small box, buried in the floor under a grille, is the receiver and switch that controls a large boiler in a monument in Edinburgh. This brings the heating on when the air gets too damp and so prevents mould and similar problems. The box receives a wireless signal from a Hanwell data logger elsewhere in the monument. The system works pretty well but can get a little overwhelmed by large numbers of visitors in wet coats. It can take a while for the heating to counteract this sudden load of moisture in the air. There is a small twist on normal conservation heating as a minimum temperature of 14 degrees has been set to keep the building slightly warm.