If you were a radio dealer 85 years ago, you wanted to be the one on the left, and not the one on the right. But it wasn’t quite that simple, as discussed in the August 1940 issue of Service magazine.

There was a wide variety of non-standard batteries for radios, and if a dealer stocked them all, there would be the problem of selling stale ones when the customer for one of the rare ones came in. So first of all, when selling new portables, you would keep your customers satisfied in the long run by selling only sets using standard batteries. In some cases, it was an underhanded trick by the manufacturer–they would design the set so that only their proprietary batteries would fit (not unlike printer manufacturers today, who make their profits from selling ink cartridges, a practice which can be beat by taking the advice on our website).

Customers were often reluctant to have you permanently change the wiring of their set to add a plug that would fit standard batteries. A good solution was often to sell them an adapter. Some were available off the shelf. In other cases, you could make an adapter by removing the socket from the old battery and connecting it to a standard plug.