Reptiles are ectotherm, and use heat from an external source to thermoregulate their optimal body temperature. Most reptiles use direct radiant heat from the sun in combination with conductive heat from sun-heated surfaces such as branches, rocks or other heat accumulating structures. Providing such an appropriate, species related, temperature gradient in the terrarium is an important factor in successful reptile keeping. With the Exo Terra Thermostats you can create a well-controlled 24-hour heating/humidifying system that allows you to maintain the required temperature and humidity conditions similar to those found in desert and tropical environments. The Thermostats will also help to prevent overheating and undercooling during hot summer days or cold winter nights. Exo Terra Thermostat Dimming SettingThe Dimming Setting of our Exo Terra Thermostats a very accurate temperature control setting that allows the use of visible light emitting heat sources. Instead of switching the power ON and OFF, like bimetallic and Electronic ON/OFF Thermostats do, the Dimming setting literally dims the electrical current sent to the heating element. The dimming Thermostat gradually increases and dims the electrical current sent to the heating element depending on the temperature increase that is needed. For instance, when the heating element is first switched on, the electrical current sent to the heating element will gradually increase until the set temperature is reached. Once the set temperature is close to being reached, the Thermostat will dim the electrical current sent to the heating element in order to maintain a perfectly stable temperature. The Dimming Setting virtually eliminates temperature swings in the terrarium. Exo Terra Thermostat Pulse Proportional SettingThe Pulse Proportional setting of our Exo Terra Thermostats is the most accurate temperature control setting for use with non-visible light emitting heat sources. Instead of switching the power ON and OFF, like bimetallic and Electronic ON/OFF Thermostats do, the Pulse Proportional setting sends the electrical current in proportionate pulses to the heating element. The pulses vary in duration and frequency depending on the temperature increase that is needed. For instance, when the heating element is first switched on, the pulses will be longer and more frequent until the set temperature is reached. Once the set temperature is reached, the pulses will become shorter and less frequent in order to maintain a perfectly stable temperature. The Pulse Proportional setting virtually eliminates temperature swings in the terrarium. Exo Terra Day/Night TimerThe Day/Night Timer of our Exo Terra Thermostats allows the daytime and night-time temperature to be set individually of each other simply and easily. The Exo Terra Thermostats should be set according to the needs of the animals. Thoroughly research the preferred optimum temperature (POTR) and humidity range for your specific reptile, so you can create the correct temperature gradients and humidity inside the terrarium to allow your reptiles to thermoregulate and maintain their moisture levels.