The starting default AC voltage detection range of the tester: About 48〜lOOOV.Press the AC voltage detection range switching button (S), the detection range indicator lights up, and the detectable voltage range of the tester is about 12〜1000V. Press the AC voltage detection range switching button (S) again, the detection range indicator lights off, and the detectable voltage range of the tester is about 48〜lOOOv. 6.Automatic shutdown function When there\'s no operation of the tester and there's no voltage signal detected by the tester within 5 minutes, the tester will power off automatically. 7 .Battery undervoltage indication When the battery voltage is lower than about 2.6V, the power indi cator flashes for 3 times,while the buzzer makes a sound and then turns off. Please replace the battery timely. Before use, specially check whether the probe is cracking or broken. If you suspect there\'s a problem, please send the tester forrepair timely. Please do not apply voltage exceeding rated voltage indicated on thetester. When testing voltage above AC 36V, be very careful, to avoid eletiicsliock. Please comply with local and national safety codes. Use proper protective equipment according to regulations of local or national authorities.