The testers have a hazardous-voltage warning light and will detect voltages even when the batteries (two AAA cells) are dead.

More importantly from a safety standpoint, the devices comply with NFPE 70E Article 110.9A), which says, "Test equipment . . . shall be rated for circuits and equipment to which they will be connected." So the units carry CAT IV 600-V and Cat III 1,000-V ratings. This makes them suited for most environments in which electricians work. Both devices have GFCI trip, an on/off switchable beeper, and a flashlight. The T+Pro features a rotary field indicator, resistance, voltage, and continuity measurement, and a backlit digital display. The T+, which is aimed at residential electricians and HVAC technicians, measures voltage and continuity.