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 circuit was found in old American documentation. Transistor is general purpose and relay is...
This simple alarm with latching uses a relay as the main element. The circuit is from a Radio...
This circuit is from an Italian publication called Fare Elettronica from 1987. What we have is an...