How does the transistor work in this circuit

AI Thread Summary
In the discussed circuit, the transistor operates as a Hartley Oscillator, influencing the sound emitted by the speaker based on switch positions. When switch S1 is down, sound is produced, and the pitch varies with the position of switch S3, altering the tuning capacitor values and thus the frequency. A lower pitch is heard when S3 is down, while a higher pitch occurs when both switches are up. The transistor's role is crucial for oscillation, and it is suggested that an NPN configuration may be more appropriate than a PNP setup. Understanding these dynamics clarifies the function of the transistor in sound modulation.
gsingh2011
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In the circuit attached, when S1 is down, a sound is emitted from the speaker. When S3 is down(connected) a lower pitched sound is heard. When S3 is up and S1 is up, a high pitched sound is heard. I don't understand why the pitch changes in those settings, and I also don't understand the purpose of the transistor in the circuit. Why does it need to be there?EDIT: To view the image you have to click on the thumbnail and then click on the image that comes up, which looks black, and then you'll see it. IDK why that's happening..
 

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Also, I think the transistor should be NPN instead of PNP with the bias voltages in the given circuit.
 
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