BJ Enterprises Sentry Tank Monitor is a self-contained, battery-operated unit designed to indicate a low or high tank level by sounding a 103-decibel siren. Engineered for use on most single- and double-walled above-ground tanks, the Sentry is primarily used by automotive and industrial markets to help prevent costly and unnecessary tank overflows or untimely inventory shortages, ideal for monitoring interstitial space as well. When activated to an alarm condition, this unit will sound its built-in siren for up to 4 days on a fresh 9-volt battery. A low-cost unit that is simple to install and easily maintained on-site, the Sentry is ideal for remote areas where AC power is not accessible. This unit also features weather-resitant housings for all its buttons, a UL buna sensor, and a 1/2" x 6' pipe that is easily field adjustable to provide a tank depth from 2" to 10'. The Sentry can not be used to run accessories.