A good columnist is never unintentionally tedious, but this week’s effort is about obsolete telephone directories, binary counter overflow, and the alternating current waveform. The boredom is the point.

Start with alternating current. As most of us once learnt and have since half-forgotten, mains electricity is supplied by an oscillating current whose direction changes rapidly. In the UK, for example, the current flips back and forth 50 times a second.

This system is highly efficient but suffers from a serious downside: if the frequency slips outside a tightly defined target range, both the system and many of the appliances plugged into it can be damaged. That almost sounds interesting, but of course it is boring after all, because electricity is generated by power stations that all but guarantee a stable, reliable waveform: heavy, rapidly spinning hunks of metal powered by steam heated by burning hydrocarbons or a nuclear reaction. Or so it used to be, but thermal generation is rapidly going out of style in favour of wind turbines that do not spin at a predictable rate, and solar panels, which produce direct current instead.