The testo 745 Non-Contact Voltage (NCV) Tester quickly checks for the presence of voltage in AC powered systems. It can be safely used up to 1000 VAC. When AC voltage is detected, the testo 745 gives indication by flashing RED LEDs and buzzing audible tones. You can easily determine the hot and neutral legs of an outlet without lengthy and risky removal of the outlet. The testo 745 NCV has a built-in Low Pass Filter which greatly reduces high frequency interference which causes false indications. The included 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 1000V and CAT IV 600 V.