Energizing a vacuum-tube flip-flop module from a 1948 IBM system

In 1948, IBM introduced the 604 Electronic Calculating Punch. This machine was a programmable calculator, about the size of a double refrigerator. It was not quite a computer, but was programmed by plugging wires into a plugboard. This machine read numbers from a punch card, performed up to 60 calculations on these numbers, and then recorded the results by punching holes in the card.1 It processed 100 cards per minute—over one card per second—and IBM advertised it as the equivalent of 150 engine...