Make your own Telegraph
Materials:
-2 electric buzzers
-two 6-volt batteries
-roll of 18-gauge wire
-2 small blocks of wood
-2 thin strips of metal
-four round-head screws
Direction:
Make two sending keys. For each, use a block of wood as a base and a small strip of metal as a sender, ask an adult to help you cut the metal from the lid of a tin can. Bind the sharp edges of the metal strip with adhesive tape so you do not cut yourself. Scrape or sandpaper the lacquer off the underside of one end to allow the electric current to pass through.
Screw on of the screws into one end of the block. This is your contact screw. Attach one end of the metal strip to the other end of the block with a second screw so that the unattached end of the strip is over the contact screw. Bend the metal upward so that it will not make contact with the screw unless pressed down.
Attach the wires as shown in the diagram. The batteries have positive and negative terminals, indicated by + and - signs. Be sure to connect the + terminal of one battery withe the - terminal of the other. Scrape off or push back the insulation at the end of a wire when making a connection so that the connection is made with bare wire. If your buzzers come with lead wires already attached, position the positive (red) leads as shown. Make each buzzer connection by twisting the bare ends of the connecting wires together. Then cover the connection with tape. To connect the wires to the sending keys. Loop the bare wire under the head of each screw and then tighten the screw against the wood.
When both keys are pressed tot he contact screws, a complete electrical circuit is formed. Electric current flows through the circuit, and the buzzers sound. To send messages, use Morse code, keeping the key down longer for a dash than for a dot. Messages can be sent by only one person at a time. When your partner is sending a message, you must hold your key down so that there will be a continuous electric circuit.