With this circuit of a Popular Electronics from the 90's it is possible to test a diode with the oscilloscope visualizing its characteristic curve. The transformer can have currents starting from 100 mA.
This Schmitt trigger was found in old documentation. The transistors can be of the general-purpose type like...
This circuit can be used with previous transmitters to decode a signal transmitted via power grid....
This circuit was suggested by General Electric in a 1965 documentation. The circuit can be...