S.T. International Aquarium Thermostat with Automatic Alert Alarm, 1200-watt Equipped with an automatic alert with alarm-controlled by a micro-chip If there is a change in temperature + or  5 F (3 C) from the preset temperature, the alarm will sound and the temp will be adjusted appropriately If the temperature increases to 95 F and above, the power supply will be cut off If below 68 F, it will continue to heat