The Wurlitzer 940 battery pack was an accessory for some Wurlitzer 140 electronic pianos. It was intended to allow the Wurlitzer to be used when unplugged from AC power. The batteries must have been substantial, because not only does the 140 require a high reed bar voltage, but the germanium power transistors used a fair amount of current to power the speaker.

As far as we know, there are no photos of the battery pack, which makes some of the technical drawings a little mysterious.