Found in a 90s Popular Electronics, this circuit provides sinusoidal signals at frequencies given by the components, as shown in the table beside the circuit.
With this circuit it is possible to use a common hair dryer as a hand dryer. The circuit is timed...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
This circuit was obtained in a 1975 magazine, but it can be easily assembled using BC548...