The Testo 745 ncv has a built-in low pass filter which greatly reduces high frequency interference which causes false indications. The built-in LED flashlight is bright and focused to make testing simple in Dark spaces. It also includes a low battery indication and is waterproof and Dustproof rated per IP 67. The Testo 745 is rated to cat III 1000 V and cat IV 600 V. Test's history of efficiency, innovation, and quality now extends into the entire electrical lineup. Once again, Testo brings high value, feature-packed products to the HVAC contractor market. made in United States. Manufactured by Testo, Inc.