Elenco Upgrade Kit SC500 to SC750 - Manual (Page 9)

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Project #512
OBJECTIVE: To make a siren that slowly starts up and fades
away.
Turn on the slide switch (S1), and then press the press switch (S2) for
a few seconds and release. A siren starts up and then slowly fades
away as the 10
μ F capacitor (C3) discharges.
Siren
Project #513
OBJECTIVE: To make a low-frequency oscillator.
Build the circuit and turn on the slide switch (S1), you hear a sound like
raindrops. The adjustable resistor (RV) controls the rain. Turn it to the
left to make a drizzle and turn to the right to make the rain come
pouring down.
You can replace the 10K Ω resistor (R4) with the 1K Ω (R2) or 5.1K Ω
(R3) resistors to speed up the rain.
Electronic Rain