This circuit from a Radio Electronics from October 1965 shows how to obtain the action of an SCR when triggering a relay using two transistors. The relay is according to the circuit supply voltage.
In the figure we have a high stability voltage reference, providing a voltage of 10 V at the...
We find this circuit in an American 1980s documentation. Integrated circuits are uncommon today as...
The diagram is from a 1990s document. The integrated circuit must be equipped with a heat sink. The...