If you do any electrical work around the house, or even if you don’t, and you want to make sure the electrician did things right, you really ought to have an inexpensive outlet tester like the ones shown here. You’ll be able to tell at a glance whether the outlet is wired correctly, or if there’s some invisible fault. Those errors could include the polarity being reversed, either the neutral or the hot not being hooked up, or the absence of a ground connection. The one shown here is available on Amazon, and they can be had at low cost at any hardware store.

But fifty years ago, they weren’t so readily available, and the home handyman might consider making his own. The plans were shown in the March 1967 issue of Popular Mechanics. As you can see, the device is quite simple. If you want to make your own, here’s the schematic: