Elenco Electronics 202 - Manual (Page 73)

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Project #163
OBJECTIVE: To build a high-frequency oscillator.
Tone Generator
Project #164
Tone Generator (II)
OBJECTIVE: To lower the frequency of a tone by increasing
circuit capacitance.
Replace the 0.02 μF capacitor (C1) with the larger 0.1μF capacitor (C2).
You now hear a low frequency sound, due to more capacitance.
Project #165
Tone Generator (III)
OBJECTIVE: To raise the frequency of a tone by decreasing
circuit resistance.
Next, replace the 1K Ω resistor (R2) with the smaller 100Ω resistor (R1).
The tone has a higher pitch now, since less resistance increases the
frequency.
Build the circuit and turn it on. You hear a
high-frequency sound.