This low cost tester checks AC/DC voltage and continuity.  All voltages between 4.5V and 380V are indicated by two light emitting diodes. If both LEDs light up, an AC voltage is present. If one LED lights up, a DC voltage is present; the polarity at the display grip is indicated by a (+) or (–) sign. Continuity can be checked in the 0 to 20kΩ range.