Buyers Products Self-Grounding Back Up Alarm Delivers A Low Frequency Tone To Warn Pedestrians And Other Drivers. It Meets Requirements Of Osha, The U.S. Bureau Of Mines, Gsa, All State Regulations, And Sae J994 Criteria. The Alarm Has A Voltage Range From 12V To 24V Dc And Can Function In Temperatures Between -22?? And 122?? Fahrenheit. It'S Epoxy-Sealed To Resist Moisture, Dust, And Vibration.