i had those as a kid, with clamp boards where you could plug in resistors, transistors, switches, diodes, a spool and in later editions even simple IC's, speakers, lamps, a potentionmeter and so on; was powered by a 9V battery and you could build a radio, flipflop's, alarm circuits and so on; i spent countless hours with that, was called Elektro Technik by Kosmos. They still have similar stuff on https://store.thamesandkosmos.com/ from what i saw, even if there aren't as many expansions as i had, but instead there's more robotics stuff (which is probably more fun for kids anyways)