Back in the day, kids were warned about things like not listening to the radio in the bathtub, or even to wear shoes in the basement. This was because caution was warranted around many electrical devices, especially the “AC-DC” radio, which was the most common design.

These circuits were such that one side of the electrical cord was often connected directly to the chassis. For some semblance of safety, there were some precautions taken. First of all, the cabinet was often made of wood or plastic, which insulated the chassis inside. Even then, though, there was often a screw visible in the back. In some cases, the connection to the chassis was through a capacitor, although that could eventually become leaky. So taking your five-tube radio into the bathroom probably wasn’t a good idea.

This hint for adding a bit more safety appeared in Radio-Electronics 75 years ago, May 1950. If the plug is plugged in with the correct polarity, then the risk of shock is minimized considerably. These days, if you’re restoring an old radio, it’s a good idea to add a polarized cord and/or a three-prong plug.  Even so, it’s probably best not to use it in the bathroom or near the kitchen sink.