The young man in this picture is now close to 100 years old, but in 1940, you can see the look of pride in his face that his dad figured out how to economize on the cost of B batteries for their portable radio. Generally, such radios required two batteries–one, often 1.5 volts, for the filaments, and another one, usually 45-90 volts for the B+.

But here, Dad purchased a converter which allowed him to run the radio from a single 6-volt battery. The power supply, apparently manufactured by Electro Products Co., 549 W. Randolph, Chicago, produced all of the necessary voltages. It could be used, as shown here, with a dry cell battery. Or, it could be used in the car, where an external antenna might also be required.

The picture appeared in the August 1940 issue of Popular Mechanics.