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.
This signal follower, from a publication from the 1970s, uses old germanium transistors such as...
This sophisticated photometer that has a light comparator with LED indicator came out in an...
The presented circuit is used to test ordinary fluorescent lamps. This circuit also has a mains...