Found in Ferranti's 1968 documentation, this circuit uses a Darlington photo transistor to drive a 12V relay. The circuit can be implemented with modern equivalent components.
This flip-flop circuit with general purpose transistors was found in American documentation from...
This circuit was found in a 90s Popular Electronics. The integrated circuit used is similar to the 741....
This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common...