Compatible with the Signet 515 and 525 flow sensor, large digital display indicates flow rate and totalized flow volume simultaneously. Four-button keypad provides for simple operation while setting screen displays and programming the system. Calibration can be easily performed by entering the AutoCal feature and entering a value to match an external reference. Long lasting lithium batteries. Requires two 3.6 V lithium thionyl chloride AA-size batteries. Low battery indication will appear on LCD display.