Metronome using operational (CB22060E)

We found this circuit in an English publication. The transistor can be BC549, and the power supply can be between 5 and 9 V.

Infrared Optical Link (CB14674E)
In the figure we have the transmitter and the receiver for an optical audio link via infrared. The...
Power Siren (CB15709E)
This circuit is indicated for applications in alarms generating an intermittent high-power tone in a...
Motor Speed Control (CB15937E)
This full wave control with SCRs uses a different solution to avoid using a diode bridge: a pulse...