Elenco Electronics 202 - Manual (Page 77)

Project #175 Symphony of Sounds
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Project #174 Changing Siren
OBJECTIVE: To build a siren that changes after a few seconds.
OBJECTIVE: To combine sounds from the music, alarm, and
space war integrated circuits.
Build the circuit shown. Turn it on and press the press switch (S2)
several times and wave your hand over the photoresistor (RP) to hear
the full symphony of sounds that this circuit can create. Have fun!
When you turn on the press switch (S2), the integrated circuit (U2) will
make a loud siren sound and the LED (D1) will light. After a few
seconds the sound will change to a different siren. Leave the circuit
off for a while to recharge the first siren.