Product Name: Phase Detector Digital Display Socket Tester Model: ST05D Power supply voltage: 250 (V) Colour: Black Plug: US/EU/UK(Optional) Voltage measurement: 1. The normal voltage range of zero fire line is plus or minus 10% of the local standard voltage. If it is too high or too low, it may be because the circuit load is too high or the power supply is too low/ too high. 2. The normal voltage of zero-earth wire is le than 2V, if too high maybe it is because there is current leakage, or the three phase-sequence is out of balance or there is signal interference in the circuit. RCD TEST: Please turn off all electrical appliances before using this function to ensure that the power outage will not cause any harm. Features: -The polarity detection of the three hole power socket wiring -The protection function detection of the leakage switch -It can quickly and accurately detect the wiring -Widely used: fire protection/laboratory/factory/family Package Included: 1x Socket Tester