SMAKN&reg; DC-DC 0.36" Digital Voltmeter 300V Limit Alarm 2/3 Wires Universal Voltage TesterRed) New high-precision digital voltmeter, with upper and lower limit voltage alarm output function. Can 3-wires, and you can change it to 2-wires. Input with anti-reverse protection. When the measured voltage below 10V, automatic transfer decimal point, increase the resolution of lo Upper and lower limit setting method: press two keys simultaneously, the red indicator(HV) light, pr