... and displays real time AC phase voltage, line voltage, and current with LED display in 3P3W or 3P4W network. It is ... is an economical and practical AC voltage/current measurement device.Model DescriptionYD9120:3 phase current, voltage input, 4 bits display,YD9121:3 ... , 4 bits display + one relay contact output,YD912A:3 phase current, voltage input, 4 bits display +one RS485 + one passive contact ...