This highly sensitive light sensor was found in a 1970 General Electric documentation. The circuit can use the 2N2646 for the UJT and the phototransistor can be of any type.
This circuit was obtained from documentation from the 90s. The solution that can be found...
This receiver powered by the signal captured by the antenna (which must be long) was found in...
This circuit measures the temperature through the voltage drop across a diode. The circuit was...