This circuit was found in documentation from the 1980s. The circuit uses several components of the time, which are uncommon today. We must not supply it with a transformerless power supply.
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,...