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.
This circuit determines the frequency of a signal by beating with a known signal. The circuit was...
With the values of the components indicated, this timer controls intervals from a few seconds to a...
The purpose of this circuit is to automatically turn a water pump on and off. Sensor 1 is the...