Dot-dot-dot-dot; dot; dot-dash-dot-dot; dot-dash-dot-dot; dash-dash-dash. That's Morse Code for hello. Named after the American inventor Samuel Morse, Morse code is a system of short dots and longer dashes which represent the letters of the alphabet. Signals are sent by starting and stopping the flow of electricity through a wire.

You can make your own telegraph for sending secret messages to a friend. This project may require a trip to the store, some patience, and maybe a bit of help, but it's well worth it. After connecting all your wires and buzzers, you'll be able to "talk by lightning" (as telegraphy was once called).

• 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)
• pliers
• tape

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 at the right shows the positive and negative connections.

1. Using wire strippers or scissors, remove about 1.5 cm of the plastic insulation from the ends of each piece of wire.
2. We will need to distinguish between the three long pieces of wire. The easiest way to do this is to put a piece of tape on each and letter one A, one B, and one C.
3. Put a bend in each of the two small pieces of cardboard about 2 cm from one end. Tape these pieces to the right side of the larger cardboard pieces. These will be the switches.



4. Tape the battery to the centre of one of the large pieces of cardboard. The positive (knobby) side should be positioned as in the photograph.
5. Tape two of the short wires to the negative (flat) side of the battery. It's important to make sure the metal from the wire is making contact with the metal part of the battery.
6. Push a tack through the larger piece of cardboard right underneath the cardboard switch.



7. Make a loop in the free end of one of the pieces of wire taped to the battery and hook it around the tack. Use pliers to bend the tack over on the other side of the cardboard so the wire won't slip out.
8. Tape the buzzer to the other side of the large piece of cardboard.
9. Twist the free end of the second wire to the buzzer's black wire. Make sure the metal parts are touching one another. It's also a good idea to wrap tape around the twist to make sure it doesn't come apart.



10. Push a tack up through the underside of the cardboard switch. When you push the switch down, the two tacks must touch.
11. Put a loop in one end of wire A, and hook it around the tack. Use pliers to bend the tack as before.
12. Tape one end of wire B to the positive (knobby) end of the battery. Remember the metal of the wire must touch the metal on the battery.
13. Twist one end of wire C to the red buzzer wire. Wrap tape around the twist.
14. Push a tack through the second large cardboard piece below the free end of the cardboard switch. Put a loop in the free end of wire B and one end of the remaining short wire. Hook both wires around the tack. Use pliers to bend the tack back.
15. Tape the light to the other side of the piece of cardboard as shown.



16. Attach the free end of the short wire to the light.
17. Attach the free end of wire A to the other side of the light.



18. Push a tack up through the underside of the cardboard switch. When you push the switch down, the two tacks must touch.
19. Put a loop in the free end of wire C, and hook it around the tack. Bend the tack back.

That's it. Pushing down on the switches completes the electric circuit and turns on the light (or sounds the buzzer) on the other piece of cardboard. If it doesn't work, check your connections: wire has to be touching wire (or tack) at each connection. If it still doesn't work, try pushing the wires more firmly against the ends of the battery.

One final note. If you are using LEDs, you may find them hard to connect to the wires. The photo below shows one easy way.

• o What does the international distress signal SOS stand for? Save our Ships, Save our Souls, Save our Saucepans? Nope, it doesn't stand for anything. It's just a combination of three dots, three dashes, and three more dots chosen by a 1903 international committee because it's easy to remember and transmit.
• o "OK" was used in 1846 by a telegraph company to say messages had been received. The expression originally came from "Oll Korrect" used in the 1840 U.S. political campaign.

A .- B -... C -.-. D -.. E . F ..-. G - -. H .... I .. J .- - - K -.- L .-.. M - - N -. O - - - P .- -. Q - -.- R .-. S ... T - U ..- V ...- W .- - X -..- Y -.- - Z - -.. Period .-.-.- Comma - -..- - Out .-.-. (message done)