It is a plug-in thermostat that is pre-set to come on at a set temp and go off at a pre set temp. Most of the ones we use on this forum come on at 35 degrees and shut off at 45 degrees. Ones that you use for farm tractors and the like come on at 20 degrees and off at 30 degrees to enable starting engines. I am not as thrilled with the thermocube as I would like to be and may opt for an in-line thermostat where I can adjust the temp points. Hop this helps.