Found in an old Popular Electronics this circuit is still current. The SCR can be of the 106 series and the relay according to the voltage used in the supply. The voltage can be 12 V.
The operational amplifier used in this circuit is not common today, but it can be implemented with...
This circuit is used to test triacs. It can be connected in series with a resistive load such as...
In the figure we have the configuration of a transistor as a temperature sensor. The circuit is...