The world is pretty standardised into these two now, but that can't always have been the case. In the early 1980s, my dad found an old valve keyboard / organ t

The world is pretty standardised into these two now, but that can't always have been the case. In the early 1980s, my dad found an old valve keyboard / organ thing at some jumble or car-boot sale that probably dated at least from the 1950s, and being curious I used to regularly take it to bits. One thing that was weird is that there was an input voltage selector on it, but it was a round thing with contacts arranged in a circle and a plug that would bridge one contact to the centre contact. The range of input voltages was 60VAC to 240VAC, and there were probably 10 or 12 different voltages in that range. Unfortunately, this was also how I destroyed the keyboard part (but not the separate valve amplifier that I continued to use for at least another decade) because the 60VAC was next to the 240VAC and I accidentally bridged it to 60VAC and fed it 240VAC. All the valves were powered at 4x what they should have been and there was a bang and nothing worked after that. In retrospect, I should probably have kept it as probably only a few valves took the brunt of power surge, but even then valves were hard to get hold of and these weren't all the same (my memory is fuzzy, but there were probably 30+ valves in the keyboard, I only pulled a few to look at them and they were obviously different), so we just decided it was something that didn't need to be repaired. But anyway, long story aside - there must have been some demand for such a wide range of input voltages for the power supply, or they wouldn't have come up with a selector switch with so many possible options.