Elenco Electronics EP-130 - Crisis Siren

-109
-
This siren
g
ives off alternatin
g
hi
g
h and low sounds
.
Slide the switch to position B and construct th
e
circuit. After you complete the wiring and slide th
e
sw
i
tc
h
to pos
i
t
i
on
A
, t
h
e power turns on an
d
t
he
speaker creates the sound of a two-pitch siren
.
This siren is made up of two astable multivibrators
.
IC 2 provides the normal beep sound. IC 1 produce
s
the signal that alters the pitch o
f
its sound at regula
r
intervals
.
L
et
’
s execute a sma
ll
exper
i
ment now.
Th
e s
i
ren
g
ives out an intermittent beep instead o
f
the two
-
pitch sound once you detach the 22k
Ω
k
resistor.
C
a
n
you decipher why? The IC 1 interrupts the siren
sound produced by I
C
2.
N
otes:
EXPERIMENT #90: CRISIS SIRE
N
W
iring Sequence:

1
-
29

2
-30

3
-
116

5
-
83
-7
0
-
108
-
112
-
121

8
5-63-131

64
-
90
-
92
-
11
5

6
5-107-89

6
6-82-84-86-91

81
-
94
-
88
-
6
7

93
-
68
-
111

69
-
80
-
8
7

7
9
-
119
-
124

122
-
132
S
chematic