This static switch or triac contactor was obtained from Philips 1969 documentation. The SCR is from the era, but modern equivalents depending on the load can be used.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...