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.
We obtained this circuit in a Maxim documentation from the 90s. The circuit is based on the...
This indicator or VU meter for stereo amplifiers was found in a 90s Radio Electronics. The...
This circuit was found in 1967 General Electric documentation. The transistors of the time can be...