Elenco Basic Electronic Experiments - Manual (Page 47)

47
EXPERIMENT #31: MORSE CODE
The forerunner of today’s telephone system was the telegraph, which was widely used in the latter half of the 19th century.
It only had two states
− on or off (that is, transmitting or not transmitting), and could not send the range of frequencies
contain in human voices or music. A code was developed to send information over long distances using this system and
a sequence of dots and dashes (short or long transmit bursts). It was named Morse Code after its inventor. It was also
used extensively in the early days of radio communications, though it isn’t in wide use today except in amateur radio (“ham”
radio). It is sometimes referred to in Hollywood movies, especially Westerns.
MORSE CODE
A
. _
I
. .
Q
_ _ . _
Y
_ . _ _
4
. . . . _
B
_ . . .
J
. _ _ _
R
. _ .
Z
_ _ . .
5
. . . . .
C
_ . _ .
K
_ . _
S
. . .
Period
. _ . _ . _
6
_ . . . .
D
_ . .
L
. _ . .
T
_
Comma
_ _ . . _ _
7
_ _ . . .
E
.
M
_ _
U
. . _
Question
. . _ _ . .
8
_ _ _ . .
F
. . _ .
N
_ .
V
. . . _
1
. _ _ _ _
9
_ _ _ _ .
G
_ _ .
O
_ _ _
W
. _ _
2
. . _ _ _
0
_ _ _ _ _
H
. . . .
P
. _ _ .
X
_ . . _
3
. . . _ _
Connect the circuit, it is the same oscillator circuit that you have been using. Press the switch in long and short bursts to
make a sound pattern representing the dots and dashes shown in the table above. You can use Morse Code and this circuit
to send secret messages to friends in hearing distance without others knowing what you’re saying. If the sound bothers
others in the room then you may send Morse Code messages using flashes of light instead. Use the same circuit as you
used in Experiment 14 (The Electronic Switch) and press the switch in the manner shown here. During World War II Navy
ships sometimes communicated by flashing Morse Code messages between ships using searchlights (they did this
because radio transmissions might reveal their presence or position to the enemy).
+9V
S
P
100k Ω
473
3.3k Ω