Found in a Popular Electronics from the 90s, this game can be seen in other configurations on this site. The circuit uses components that are still common today.
This precision full-wave rectifier used in instrumentation was found in a technical documentation from the...
In the figure we have the way to control the frequency of an oscillator with a NE602 using a...
This filter was found in a publication for radio amateurs in 1977. The components can be changed for...