Filtersmarts Electro-Optical Heating/Cooling System Sensor

* Flashing indicator - flashes when filter becomes clogged
* Buzzer indicator - beeps (quad beep) after 2-1/2 days of "change filter soon" indicator flashing
* Reset switch - tells sensor to store measurement of clean filter -Provides automatic adjustment for filters of different optical densities (pleated or non-pleated sensors)
* Fits most filter installations
* Assembly required
* 9-Volt battery not included