HM Digital's QC-1 is a "Push-to-Test" TDS monitor designed to monitor the effectiveness of the water filter for your spot-free rinse. The unit is battery operated and can be easily installed within minutes. It has eight programmable settings (by dip switch) ranging between 1 and 50 ppm. Once installed, a user simply needs to press the button. If the filter is operating effectively, a green light will illuminate. If the filter needs to be changed, then a red light will illuminate. It’s backed by a one-year warranty.