Rugged CAT IV NCV with Visual and Adible Live Wires Indicator Use DV23 to quickly check for the presence of live wires before performing any electrical testing. Suitable for outlets or against wire insulation testing, this AC Voltage Detector for non-contact detection of AC Voltage from 50 to 600V (50/60Hz). Red LED indicates the presence of voltage. CAT IV 600V safety rating. Comes with two AAA batteries.