The PRV240 works with both AC and DC equipment, producing a very specific voltage reading when activated--if your tools are working correctly, they should see "240 Volts." If they give you anything else, it's time to take a step back and check your gear!
Even though this was a relatively simple project, we still explored multiple form factors and ergonomic positions, paying particular attention to what happen when the user applied pressure to the input jacks while performing a test. In the end, a face-up design with a flat bottom was chosen.
The PRV240 design incorporates Fluke's trademark "Toolpak" magnet + strap accessory, making it easy to hang or mount to a variety of surfaces. This is a great convenience to the user -- some teams even like to mount one near their shop door, so everyone habitually validates their tools whenever they leave to go do a job.