This is one of the many possible siren configurations for the 555 integrated circuit. We found it in the October 1992 Radio Electronics magazine. It has a power stage.
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This old fashioned amplifier can source some watts to a low impedance loudspeaker. The circuit...
This 50 Hz rejector or notch filter was found in a 1975 documentation. Other frequencies can be...