HMS Series Overview Virtually Unbreakable Titanium Tube High Temp Resistant Heater Guard Out of Water Sensor Protection Audio Alert Over Heating Audio Alert 3 Digit Digital Display & Control 1/10th Degree Temperature Calibration Temperature Saving Memory Protection ± .5°F High Precision Accuracy Temperature Steady Low Variance Technology The HMS heater series uses an advanced digital processor that monitors and controls the water temperature in your aquarium. The heating controller receives temperature data from the remote sensor in the aquarium. The remote sensor contains no bi-metallic contacts to arc, corrode or wear out. This allows HMS heaters to have precise control, keeping the water temperature stable while avoiding wide temperature swings common with low-quality aquarium heaters. The controller displays the current temperature, allowing you to easily make temperature adjustments on the front panel. Temperature can be adjusted by a tenth of a degree. The remote sensor also functions as an automatic power cut-off switch. If the water level drops too low and exposes the temperature sensor to the air, power to the heater tube is turned off. This prevents over-heating of the aquarium, saving your prized aquarium life from harm. The heater is constructed of corrosion-resistant titanium, making it safe for freshwater and marine aquariums. The heater tube is virtually unbreakable and features a protective heater guard to prevent aquatic live from accidentally coming in contact with the heating tube. Maintenance: Secure the out-of-water sensor directly beneath the sensor cord clip, without any cord slack, and above the heating element at all times.  Clean and confirm the out-of-water sensor is functioning properly every 30 days. Do not use heater if the out-of-water sensor is inoperative.  Refer to the instruction manual for proper maintenance and care.