• two pieces of cardboard
approximately 20 cm x 10 cm
• two pieces of cardboard approximately 3 cm x 8 cm
• three pieces of wire approximately 19 cm long
• three long pieces of wire (see note)
• one new "D" cell battery
• four thumbtacks
• two lights (see notes)
• wire strippers (or scissors)
If you want to build this project so you can communicate with
a friend/brother/sister in another room, the three long pieces
of wire need to be long enough to reach that room. You can also
build the telegraph with shorter wires and then replace them with
longer wires later.
The lights can be replaced by buzzers
or light emitting diodes (LEDs: semiconductors which glow when
electricity flows through them; used as power indicators on computers
and other electronic gadgets.) All of these are inexpensive and
available from Radio Shack or similar electronics stores. The
“D” cell battery used in this project is 1.5 volts
so it’s important to buy compatible 1.5 volt LEDs, buzzers,
or lights (we used a 2.37 volt light bulb which worked fine).
If they are not available, don’t worry, you can simply tape
two batteries together. Of course, you can mix-and-match: use
a buzzer in one room and a light in the other.
Buzzers and LEDs only work if the electricity
flows in the correct direction. So you have to pay close attention
when connecting them. On the buzzer, the red wire indicates the
positive side, and the black wire indicates the negative side.
On a LED, the long side usually means positive. You can also look
to see if one side has a flat spot. If it does, that is the negative
side. The circuit diagram below shows the positive and negative