Manual

-108-
T
he sirens in Projects 88 and 89 (“Sweep Oscillator”
and “Falling Bomb”, respectively) adjust the pitch
only in one direction. This circuit makes a low sound
t
hat becomes higher, and goes back to its original
low sound. The siren sounds only when you press
the key.
Set the switch to position B and build the circuit.
Turn on the siren by sliding the switch to position A.
When you press the key, the siren starts over at the
original low pitch. Do you hear the siren sound
change pitch? Does it do so as you expected? IC 1
is an oscillator that produces a triangular signal
when you press the key. Then the output is sent to
IC 2, which acts as an astable multivibrator.
See how the pitch changes when you set C to
0.02mF and then to 0.1mF.
N
otes:
EXPERIMENT #89: ALERT SIREN
Wiring Sequence:
o 1-29
o 2-30
o 3-116
o 5-70-108-137-121
o 80-63-132
o 64-90-92-115
o 65-89-107
o 66-82-91
o 81-67-118
o 78-79-68-117
o 69-119-124
o 77-138
o 122-131
Schematic
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