23 December

Scientists at AT&T’s Bell Laboratories first demonstrate the transistor

1947 Before transistors, the sort of electric currents used in audio systems, radio and television receivers and the like were managed by thermionic valves (or vacuum tubes in American usage). They looked a bit like old-fashioned light bulbs. Depending on the wiring and where the signal was put in, tubes/valves could act as amplifiers or switches or detectors, enlarging the signal or shutting it off, or separating it out from the high-frequency carrier wave needed to send it from broadcaster to receiver. But they used a lot of power, generated a lot of heat, and often blew out – just like light bulbs.

At the Bell labs, William Shockley and his team found that crystals of silicon or germanium ‘doped’ (grown) with impurities like boron or phosphorus would become semiconductors – that is, materials that neither conducted electrical currents nor insulated against them, but performed something in between these functions. When they sandwiched the semiconductor in between two conducting plates, they found that small variations of current applied to the sandwich ‘filling’ would control large flows across the device as a whole. So the transistor could act as a valve, amplifying current or switching it on and off.

That’s the simplest model. Transistors soon grew into a bewildering variety of design and function. But their ability either to amplify or switch meant that they could be used in binary computer processors and memory, in place of those banks of valves that used to occupy floor after floor of old mainframe computers – back in the days when ‘mainframe’ was a literal description.

The final stage was the integrated circuit. Transistors and other components could be assembled, not by soldering but by being layered on to circuit boards, then assembled as microchips so tiny that it takes a microscope to see the connections.

So what has this got to do with literature? Simply that the microchips underpin the way modern books, newspapers and magazines are written and produced – and increasingly read. In its impact on literacy, the invention of the transistor may not yet rank alongside that of the printing press, but it’s catching up fast.