This circuit uses a diode as a radiation sensor. The operational ones are old because the publication is from the 80's, but modern low voltage equivalents can be tested.
Any JFET can be used in this circuit suggested by Electronics Now magazine, April 1993. The...
This circuit allows you to view two low frequency signals on a single channel oscilloscope. It was...
Found in an old Popular Electronics this circuit is still current. The SCR can be of the 106...