Elenco 130-in-1 Electronics Playground - Manual (Page 25)

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XI. TEST AND MEASUREMENT CIRCUITS
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With this experiment you may want to be careful not
to confuse your neighbors. This experiment sounds
as like a loud siren just like the real sirens on police
cars and ambulances. The tone is initially high but as
you close the key the tone gets lower. You are able
to control the tone just as the police and ambulance
drivers do.
The oscillator circuit being used is the same type
used in many other experiments in this kit. Press the
key and another capacitor is added to the circuit to
slow the action of the oscillator circuit.
Notes:
EXPERIMENT #14: PATROL CAR SIREN
Wiring Sequence:
o 1-29
o 2-30
o 3-104-106-110
o 4-85-120
o 5-41-109
o 40-137-105-86
o 103-138
o 42-119
Schematic