Klein Tools ET40 Is An Electronic Ac/DC Voltage Tester. It Features Indicators For Positive and Negative DC Polarity, and Tests DC Voltages As Low As 1.5V. It Tests Ac Voltages 12-240VAC. Excellent For Checking, Verifying or Troubleshooting Common Residential Electrical Wiring In Electrical Outlets, Light Fixtures, Doorbells and More. It Operates On 2 X AAA Batteries.