This tool can be used to detect the polarity of the three-hole power socket wiring, and this tool can be widely used in your home, factory, laboratory and other places. If you are looking for this tool, come and have a try, it will not let you down. Features: Portable Size: The small size of this tool is very convenient for everyday use, you can carry it in your tool bag without taking up too much storage space. Large Color Screen: The large screen allows you to read the data more clearly, you can use it even in the dark. This tool can be used to detect the polarity of the three-hole power socket wiring, the protections function detection of the leakage switch and quickly and accurately detect the wiring. RCD Test: You should turn off all electrical appliances before using this function. Then you can insert the tester into the socket, and make sure to pre the RCD button when the display prompts "correct wiring" (preing time is30mA RCD working voltage: 220 V20V Power: 2 * AAA batteries (NOT INCLUDED) Package size: 70 * 70 * 65mm / 2.8 * 2.8 * 2.6in Package weight: 105g / 3.7ounce Note: If zero-fire line voltage is too high or too low, it may be because the circuit load is too high or the power supplys is too low/ too high. Zero-ground voltage is generally le than 2V, such as high voltage may be the circuit leakage current, three-phase power imbalance or interference signal in the circuit. Packing list: 1 * Socket Tester 1 * Manual