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Working of a Telegraph

Working of a Telegraph

Introduction: (Initial Observation)

The telegraph was the only long distance instant communication device until radio and other means came along. Railroads were always the largest users of the telegraph and utilized them for more than a century. The railroads would have had a very hard time operating safely and efficiently without them.

The Telegraphic Apparatus invented by Samuel Morse in 1833 consists of a signal key for breaking and closing the circuit, and an electro-magnet, the armature of which is attached to a lever carrying a steel point or style, which embosses a mark upon a narrow strip of paper, moved uniformly along by clock-work. As long as a current continues to flow through the coils of the electro-magnet the armature is attracted, and the mark is made upon the moving paper. As soon as the circuit is broken the armature ceases to be attracted, and is withdrawn from contact with the paper by means of a spring. The duration of the current, and consequently the length of the mark, depends upon the duration of the contact made by the key.

The Morse Signal Key is shown in the above figure. It consists of a brass lever, A, four or five inches in length, which is hung upon a steel arbor, G, between adjustable set screws, D D, in such a manner as to allow it to move freely in a vertical direction. This movement, however, is limited in one direction by the anvil C, and in the other by the adjustable set-screw, F.

Paper telegraph was used until 1849, when telegraph operators noticed that they can read the code, just by listening to the sound of the REGISTER. So they designed a SOUNDER – mounted in a wooden box (a resonator) to mechanically amplify sound. Most later telegraph systems were a pair of key and sounder.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.  

Project advisor

Please be careful not to hurt yourself while building a telegraph set. The improper use of tools during construction can cause serious injury. The original designer of the set and the maintainer of this web page accept no liability for injuries caused by the construction or operation of the set.

Information Gathering:

Find out about Morse code and telegraph system. Read books, magazines or ask professionals who might know about the history of telegraph, Morse code or telegraph apparatus. Keep track of where you got your information from.

Search the internet with keyword such as “Telegraph” and “Morse Code”.

Following table shows the international Morse code. As you see it consists of dots and dashes. If the duration of a dot is taken to be one unit then that of a dash is three units. The space between the components of one character is one unit, between characters is three units and between words seven units. To indicate that a mistake has been made and for the receiver to delete the last word send …….. (eight dots).

International Morse Code

Letter Morse   Letter Morse   Digit Morse
A .-   N -.   0 -----
B -...   O ---   1 .----
C -.-.   P .--.   2 ..---
D -..   Q --.-   3 ...--
E .   R .-.   4 ....-
F ..-.   S ...   5 .....
G --.   T -   6 -....
H ....   U ..-   7 --...
I ..   V ...-   8 ---..
J .---   W .--   9 ----.
K -.-   X -..-
L .-..   Y -.–
M --   Z --..


Letter Morse Punctuation Mark Morse
Ä .-.- Full-stop (period) .-.-.-
Á .--.- Comma --..--
Å .--.- Colon ---...
Ch ---- Question mark (query) ..--..
É ..-.. Apostrophe .----.
Ñ --.-- Hyphen -....-
Ö ---. Fraction bar -..-.
Ü ..-- Brackets (parentheses) -.--.-
Quotation marks .-..-.

If the duration of a dot is taken to be one unit then that of a dash is three units. The space between the components of one character is one unit, between characters is three units and between words seven units. To indicate that a mistake has been made and for the receiver to delete the last word send …….. (eight dots).

Listen to the sound of Morse codes.

Click Here to access an online Morse Code Translator

Question/ Purpose:

The purpose of this project is to learn who telegraph system works. We will make a working model of a telegraph system and use it to test sending messages.

Identify Variables:

We will study components of a telegraph apparatus and coding system that is used to transmit messages.


My hypothesis is that a combination of sound signals in a telegraph system, represents a character, so a telegraph operator must listen to the signals and interpret the message.

Experiment Design:

The main focus and purpose of this project is to understand the Morse code and logics ant techniques used to send messages, not the mechanics and equipment. If you have any other method to obtain a telegraph system for test, you will not have to make your own telegraph system.

Experiment 1:

In this experiment we will first make a simple telegraph set and then use it to transmit some messages.


you will need a small buzzer, a push button switch, a 6 volt battery and some wires.


Connect your battery, the switch and the buzzer in series and close the circuit by connecting the two open ends. Now by pushing the button, the buzzer must make sound

A BATTERY supplies the electricity or voltage.
A KEY is used to complete or break the circuit.
A BUZZER is used to generate the sparks and the radio waves.

The circuit is shown below: (The lines indicate the wires and the arrowheads show the path of the electrical current as it flows through the wires.)

!—>—->—->—— BATTERY —->—->—->—–!
!                    (Supplies the voltage)                       !
KEY                                                                 BUZZER
(Completes or breaks                                      (Generates sparks
the electric circuit)                                          & radio waves)
!                                                                        !


The WIRES can be virtually any kind of electric wire with the insulation removed from the ends where the connections are made.

The BATTERY can be flashlight or lantern batteries generating about 6-Volts.

The KEY can be any electric switch or a simple piece of metal which can be bent down to make an electrical contact.

The BUZZER can be a door buzzer which can be found in any hardware store. You can also make a buzzer by removing the bell from a doorbell.

Pressing the telegraph key completes the electrical circuit and allows electricity from the battery to flow through the sounder’s coil and it makes a clicking sound as the metal strip strikes the nail in the center of the coil.

Releasing the telegraph key allows the metal strip to spring upwards and strike the other nail, making a different click.

You may use up to 100 feet of wire between the key and the sounder.

Use your device to produce Morse code and send messages to a friend in the same room. If you want to transmit code to a distant location, you will need two sets of keys and buzzers and some wires.

Experiment listening to Morse code and recognizing the codes or writing them down.

Also experiment creating the codes using your computer keyboard and the code translator program.

Experiment 2: (optional)

The following project is the simplest functional telegraph system construction project that I could find. It requires very few parts and all of them should be commonly available.


Material used in this experiment are:

  • 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.)
  • 4 Flat strips of metal. Three of them should be about 4 inches long.
    One should be about 7 inches long and MUST be iron-bearing or “ferrous” metal which is metal that is attracted by a magnet.
    (This kind of metal is often found in food cans.)
  • 20 ft or more of INSULATED solid wire.
    (22 – 30 gauge…. about 1/64 inch or less in diameter.)
  • 2 Flashlight batteries.

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

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 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.

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.

Materials and Equipment:

Material list can be extracted from the experiment section.

Results of Experiment (Observation):

What did you learn from experimenting Morse code. Is Morse code still useable? Can you use other devices to send Morse Code? Does Morse code and telegraph system has any relation to future developments of Telex, Teletype and Computer?


Nor required.

Summery of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


List of References

Questions and answers:

Q. “I built a prototype using two strips of sheet metal screwed down to a piece of wood for the switch or key to switch the electricity on or off.”

“I used a nail as the core of my electromagnet and I wound 100 turns of insulated wire around the nail. I mounted the nail so that it would attract a piece of springy iron when it was activated. (at first, I used a piece of aluminum or copper metal and discovered that the metal had to be iron or ferrous metal for the magnet to be able to pull on it).”

“I connected them all as in your diagram and used a battery holder and two “D” size flashlight batteries to provide the voltage.”

“When I push the key, it brings the two pieces of metal together and completes the electrical circuit. The electromagnet then pulls in the piece of springy iron and it makes a nice click.”

“I can’t figure out how to differentiate between a dot and a dash when all I get is a click”. (All he needs to do is to put a second piece of metal up OVER the piece of springy sheet metal of the sounder to make a second click. when the sounder releases, and he will have made a complete replica telegraph system. – – see detailed explanation below – -)

“I built another prototype hooking a buzzer to the circuit instead of the sounder. That took care of the problem of telling the difference between a dot and a dash, but it isn’t much of a challenge or learning experience for the kids.”

“Any help or suggestions would be appreciated.”


A. What a great project! Congratulations on creating a working system like that… Yes, It is easier to have the kids learn to use a buzzer than to use a clicking “sounder”. A doorbell buzzer, available in hardware stores approximates the early buzzer sounds quite well.

The sounders used from 1850-1950 were like your nail/solenoid…. IF… you were to modify it by putting a piece of metal OVER the piece of sheet metal that is moved by the electromagnet. This would give you a system that made a click when the electromagnet pulled IN and a slightly different clack when the electromagnet released.

Sounders all make a slightly different sound when they pull-in rather than release and the operator learns to discriminate between these two different sounds and soon unconsciously can tell a dot from a dash.
Click-in..clack-out is a dot.
Click-in…………..clack-out is a dash.

That might be a bit of a challenge to learn so you might want to go to the buzzer system used from about 1910 to 1950.

You could also try using very different metal parts to strike on the pull-in and release to make the sound difference even more noticeable.

You could also use a light bulb as an adjunct to the sounder and have it go on whenever the sounder was activated. This might help the kids learn to copy the code.

You could also mount a pencil on the sounder arm and have it mark a piece of paper with either a high mark or a low mark while the paper was pulled under the pencil at an approximately constant speed. This would approximate Samual Morse’s very first telegraph systems used before people learned to copy code by ear. Morse invented a “register” which used a clockwork mechanism to pull a paper tape under a pencil which was moved in and out by an electromagnet.

If you used this system, you could translate the short downwards pencil marks on the paper as dots… and the long downwards pencil marks on the paper as dashes…

Good luck with your project.


Overheating and dead batteries

One parent emailed that all his completed set did was to have the coil of wire get very hot and that the battery went dead shortly afterwards.

After asking him a few questions, I found out that he had wound bare (uninsulated) wire around the nail. I explained that the coil of wire had to be made from insulated wire so that the individual turns in the coil did not electrically connect to each other.

Sticking Sounder:

One parent noted that closing the key caused the electromagnet to attract the metal armature of the sounder but that it did not release after the circuit was opened.

I suggested increasing the strength of the springiness of the metal that pulled the armature away from the nail…
….. AND
INSERTING a very thin piece of plastic sheeting or wrapping material between the nail and the armature to prevent the metal armature from directly coming into contact with the nail.

PLEASE let me know if you have problems or solutions that might be of interest to other builders…
Good Luck with your project… and don’t forget to send pictures…