Found in a Popular Electronics from the 90s, this Wien bridge oscillator uses a single-source operating. The frequency can be calculated from the formulas in the previous circuit.
This encrypted key was found in a 1989 documentation. It controls a relay that is activated only...
This circuit is from an American transistor book from the 60's. The transistor is germanium of the...
This simple SCR alarm circuit was found in an old Poptronics, but can be easily assembled as all...