Elenco 130-in-1 Electronics Playground - Manual (Page 108)

-108-
The 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
that 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
0.02
μF and then to 0.1μF.
Notes:
EXPERIMENT #89: ALERT SIREN
Wiring Sequence:
1-29
2-30
3-116
5-70-108-137-121
80-63-132
64-90-92-115
65-89-107
66-82-91
81-67-118
78-79-68-117
69-119-124
77-138
122-131
Schematic