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How to Build a Morse Code Telegraph

Here are the instructions on how to build a Morse code buzzer and telegraph. We also have plans for a simpler buzzer. If you aren't sure which you would like to build, you can start with the simpler buzzer because it uses the same parts. You can use either buzzer to learn Morse code or to use in the classroom.

How it Works

The telegraph is very similar to the simple buzzer project, but it includes a light (LED) and a connector that you can attach to another buzzer to create a simple telegraph. By connecting more than one buzzer, you can signal someone with another box across the room.

To use the buzzer, simply press the button and the light will light and the buzzer will buzz. To buzz another box, first connect the two with the connecting wire. When the button on either box is pressed, the buzzers and lights on both boxes will operate.

Parts List

The buzzer and telegraph is simple to build, all you need is a button, a buzzer, a LED, a battery, a connector and a battery holder. All of these parts are available from Radio Shack:

• 12 Volt Buzzer (Radio Shack part # 273-055, $2.59)
• 12 Volt LED (Light Emitting Diode) (Radio Shack part # 276-011, $2.29)
• Momentary Button (Radio Shack part #275-609, two in a package for $2.79)
• 2.5 mm 2 conductor jacks (Radio Shack part #274-247, two in a package for $1.99)
• 2.5 mm 2 conductor plugs (Radio Shack part #274-289, two in a package for $1.89)
• 9V Battery Clip (Radio Shack part #270-325, five in a package for $1.39)
• 9V Battery (Radio Shack part #23-783, $1.29)
• Project Box (Radio Shack part #270-221, $2.29)
• 2 conductor wire (Radio Shack part #278-1509, $3.49 for 22 m (75 feet))

The total cost per buzzer is $12.04, plus $3.49 for the wire. It costs a little more if you only build one buzzer because battery clips and buttons come with more than per package. To make a complete telegraph, you will need 2 buzzers and a connecting wire. The total cost is $28.47 for a complete telegraph with 2 buzzers.

All of these parts are available from Radio Shack. The people at your electronics store may be able to recommend equivalent parts if they don't carry these exact parts. If you do not have a Radio Shack or other suitable electronics store near you, you can get these parts by mail order by calling 1 (800) 843-7422. (1 817 624 1196 for orders outside of the United States.) TerraX.org is not affiliated with Radio Shack in any way, this is just any easy way for everyone to use the same part numbers.

1. First you need to build two or more buzzer boxes.
2. Cut an appropriate length of 2 conductor (2 wire) cord for your purposes.
3. Add a 2.5 mm plug to each end of the cord.
   • Unscrew the plastic cover from the plug and slide the cover over the end of the cord so that the threads face the end where the plug will be attached.
   • Strip 1.5 cm (1/2 inch) of insulation from each end of the cord. This will reveal two wires.
   • Attach the wires to the contacts by sticking them through the holes in the contacts and then soldering them. You should use electrical tape to keep the bare wires from touching each other. There is no danger if they touch, but the buzzer will always sound! The order of the wires is unimportant, you cannot connect the wrong one to the wrong contact.

Testing the Telegraph

1. Press the button on the box, the LED should light and the buzzer should buzz.
2. Connect two boxes together with the telegraph wire. When either button is pressed, both LEDs should light and both buzzers should buzz.

Troubleshooting

Hopefully everything worked fine the first time, but in case something was mixed up, here are a few suggestions:

• Check to make sure that the battery is connected properly and that all of the wire connections are tight.
• Check to make sure wires that aren't supposed to touch don't.
• Both the buzzer and the LED are sensitive to + and - voltage. You should be able to follow the red wire from the battery to the button, through the button out to the red wires of the buzzer and the LED. Likewise the black and yellow wires from the buzzer and the LED respectively should be connected to the black wire at the battery.
• If the buzzer stays on, check to make sure that the wires are properly connected to the button and the jack.

That's it, you're done!

Visit the Morse code page or the teacher's lesson plan.

Notes and Schematic

We have included a schematic for those of you that are interested.

NOTE: You may have noticed that the LED and buzzer are both "12 volt" items, yet we have only specified a 9 volt battery. Both of the specified parts work well with only 9 volts. If you should replace either one with a different part, you may want to check that it works with 9 volts.

Optional Options

• You can remove either the buzzer or the LED light.
• If you don't need the telegraph option, you can build the simple buzzer instead.
• You can attach more than two buzzers to a telegraph line, simply add an extra plug for every box that you want to add.

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