This circuit is powered by a voltage of 4.5 V, being common in radios of the 60's. The circuit is from Mullard's transistors reference manual.
This circuit was found in an old American documentation. The integrated circuit used is uncommon...
In this circuit, the current in solenoid X1 can be adjusted and its intensity measured to the...
This circuit is from a Popular Electronics from the 90s. It uses an opto-coupler with SCR directly...