Simple Two Transistor Audio Oscillator That Produces Loud Sound

This video is a demonstration of a two transistor audio oscillator that produces a loud audible sound. The circuit consists of a PNP and an NPN transistor that are directly coupled. This circuit differs from the previous circuit is that the PNP and NPN transistors are interchanged. The base of the NPN transistor is connected to the collector of the PNP transistor. The emitter of the NPN transistor is connected to the ground and the collector is coupled through a loudspeaker to the positive supply line. The base of the PNP transistor is coupled in series with a resistor and capacitor to the collector of the NPN transistor. The base of the PNP transistor is connected to a resistor in series with a variable resistor to the negative supply line. The variable resistor can vary the frequency of this RC audio oscillator. The entire circuit is powered using a 9 volt battery.
The output from this circuit produces a loud audible sound. This circuit is used for in producing alarm sound, burglar alarm, emergency alarm, audio tone signal, audio oscillator for electronic devices, toys, etc.