Building Your Own Telegraph

Over the past five years I have built around eight telegraphs for other teachers and for use in my classroom. Bellow is a simple plan to build a telegraph. I have started to include some of my modifications below for unique models to allow for more student exploration.

PARTS LIST:

  • 2 Pieces of wood. (Any kind of wood will do fine.)
  • 9 Small wood screws or nails.
  • 2 Large IRON nails.(About 2-3 inches long.)
    (NOTE: It is important that these be IRON or STEEL nails. Aluminum and copper nails will not work.)
    (You can test these nails to be sure that they are Iron or Steel by making sure that a magnet is attracted to them or by holding a magnetic compass against them to see if it deflects the compass needle.)
  • 4 Flat strips of bendable metal. (Metal pipe strapping)
    Three of them should be about 4 inches long.
    One should be about 7 inches long.
    The long one MUST be iron-bearing or so-called “ferrous” metal which is metal that is attracted by a magnet.
    (This kind of metal is often found in some food cans.)
    (Be careful not to cut yourself as you cut the strips of metal !)
    (You can test this metal strip to be sure that it is ferrous by making sure that a magnet is attracted to it or by holding a magnetic compass against it to see if it deflects the compass needle.
  • 20 ft or more of INSULATED solid electrical wire.
    (22 – 30 gauge…. (the metal part of the wire should be about 1/64 inch or less in diameter.) (The MORE turns of wire you can wind around the nail, the stronger its magnetism will be and the better it will work.)
  • 2 Flashlight batteries. (The “D” Cells shown work best.)

CONSTRUCTION:

Construction of the telegraph set is very simple. Just look at the photographs and you will see how it is put together.

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BE CAREFUL NOT TO CUT YOURSELF ON THE EDGES OF THE METAL STRIPS.

If children will be using the set, you will want to round all sharp corners with a file or sandpaper and perhaps put tape over any exposed sharp edges.

The key is made by screwing one of the strips of metal to one of the pieces of wood so that pushing down on the strip brings the strip into electrical contact with the screw that is mounted under it.

The Battery Holder: is made by screwing two of the metal strips to the wood so that they can make electrical contact with each end of the lineup of the two batteries. A rubber-band may be used to maintain pressure on the battery contacts.

Be sure to put the batteries in the holder with the positive tip of one battery pushing against the negative bottom of the other battery. This is called a “series connection” of the batteries and adds the 1.5 volt voltage of one battery to the 1.5 volt voltage of the other battery to produce a total of 3 volts. Most flashlights are designed this way.

The Sounder: requires a bit of care in construction and adjustment.

The electromagnet coil consists of one of the iron nails with at least 100 turns of the wire wound neatly around it. ( If possible wind on 200 or more turns to make the magnetic force stronger. )

The longer iron-bearing strip of metal is screwed to the wooden base and bent so that it extends up and over the top of the nail. This piece has been labeled “IRON-BEARING” in the parts photograph to indicate that it is pulled in by the magnet. Many food cans are made of this type of metal. Be careful not to cut yourself on any sharp edges.

When the electric current passes through the coil of wire, it makes the nail into an electromagnet which pulls the strip of metal down to the nail and makes a clicking sound. (You may have to carefully adjust the strip of metal so it is close enough to the nail allow it to be pulled down by the magnet.)

The second nail is important because it keeps the strip of metal from pulling too far away from the electromagnet. It also serves to make a clicking sound when the strip of metal is released by the magnet and moves upward.

To complete the telegraph set, simply connect the key, batteries, and sounder with the wires as shown in the first picture.

OPERATION OF THE TELEGRAPH SET:

When you push down on the telegraph key it completes the electrical circuit from the key to one end of the coil and from the other end of the coil to one end of the battery and from the other terminal of the battery back to the other side of the key.
Now the sounder magnet should pull down the metal strip and make a CLICKING sound. When you release the key, the metal strip should spring upwards and make a CLACKING sound.
(If it does not work, please see the “Troublshooting section below.)

You can learn to tell the difference between the dots and the dashes of the Morse code by learning to tell the difference between the pull-in “CLICK” and the release-“CLACK”.

The pull-in “CLICK” is the sound the metal strip makes when it is pulled in by the electromagnet coil and strikes the nail which is in the center of the coil.

The release “CLACK” is the sound that the metal strip makes when it is no longer pulled by the electromagnet coil and it moves rapidly upward to strike the upper nail.

The Morse Code Characters are called DOTS (or ‘dits’) and DASHES (or ‘dahs’) They are made from the CLICKS and CLACKS as follows:

A DOT is created when there is just a LITTLE time between the pull-in CLICK and the release CLACK.
Try it now: Push the key and quickly release it.
Did you hear the CLICK followed quickly by the CLACK ?
That was a DOT in Morse code.

A DASH is created when there is a LONGER time between the pull-in CLICK and the release CLACK.
Try it now: Push the key and after a short wait, release it.
Did you hear the CLICK followed after a short wait by the CLACK ?
That was a DASH in Morse code.

Now let’s send the letter “A”.
In Morse Code, the letter “A” is: DOT DASH. (or Dit Dah).
Push down the key and release it quickly to make a DOT and then push down the key, wait a bit, and release it to make a DASH.
Try it! You have just sent the Morse Code letter “A”.