Sort of implies that copper smelting was really the important innovation, to warrant the need for electricity? In all seriousness though, the printed circuit b

Sort of implies that copper smelting was really the important innovation, to warrant the need for electricity? In all seriousness though, the printed circuit board might be a good one to bundle with that. The old methods of creating a mechanically robust compact electrical package were nowhere near as efficient. They're also very recent and very easy to make yourself, even if it's thin plywood with tinfoil glued on.