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Teletype, telex or TTY: what is it, what is it for and how does it work?


This German device was booming at the end of 1945 and gained wide acceptance in the postal companies of European governments due to the practicality of implementing this system.

In this article, we will show you what a telex is and what it is for . In addition, we will talk about its origin and evolution to this day and we will tell you who are the people who use this tool today .

We bring you all the information you need to know about a TTY. Continue reading until the end of this article and you will find out all the details.

What is a teletype or TTY and what are these devices for? ?

TTY or teletype is a device similar to a typewriter . It has an alphanumeric keyboard that manages to write messages for later sending. It also allows you to receive typed messages from point to point, joined by a telegraph cable for later printing.

The most modern models use a screen, on which you can print telephone communications. At present this mechanism is obsolete, but it is used in people who have hearing problems so they can get the telephone conversation in print.



This telegraphic device has its origin in Germany, in the mid-20s of the last century . It was used for the postal service of the Reich with which it was possible to transmit a little more than 60 words per minute. After the end of World War II it was possible to expand to the whole world.

After more than 50 years of its creation , the postal services of the main European governments initiated shortwave radio links, the standard being the “R.44” , belonging to the “ITU Telecommunication Standardization Sector” . Where the transmission of the data was done by a division in time according to time slots cyclically, resulting in a set of bits.

The system that had communication was done through direct current . Where it is interrupted in a very similar way to dialing a landline, using a starting point and a space line, ending again with a point to define a cycle.

Evolution and history

Most of these teletypes used the 5-bit code (called Baudot or ITA2) , which had a limit of 32 characters . Where, to enter some special character numbers, exclusive keys should be used for these.

At the beginning the equipment used a bit for start and stop, due to its electromechanical design. As time went by the devices became synchronous, the task of synchronizing their mechanical components being often difficult.

So it was decided to continue using the 5-bit Baudot code , where special versions were created to be able to apply them in certain reports, such as weather reports.

Postal and telegraph services that did not have large financial resources performed their operations on TOR or telex channels -radio to obtain a greater value from them. In this way over time the cost of these equipment was decreasing considerably and from 2016 people who are radio amateurs use this shortwave system known as RTTY .

How does a telex work to send and receive typed messages?

This equipment has a keyboard for writing and a receiving device that is used to print the reception of messages . Which are done through printed characters defined by electrical signals, which consist of different combinations of electrical impulses, both positive and negative.

In this way different characters are sent and they are interrupted according to an encryption predetermined by some standard. It is a system very similar to a fixed telephone dialing. Once the characters have arrived at the receiving telex, it begins printing them according to the standard assignment.

Telex vs Fax Which is better and how is each one?

While it is true that both devices have a similar physical appearance (considering the latest teletypes, since in their principles they were large and heavy) , the technological difference that exists in each of them is very big.

Since with telex you can send and receive messages through an integrated keyboard , while with a fax also, there is a messaging service, but you can incorporate images that the first does not support mechanical equipment.

In addition, the texts generated in the fax are not created on the same device, but a separate text computer is needed to get a written message.

In this way, we can conclude that a fax is much better today to send and admit messages that is a telex. This is because, not only can you send or receive texts, but you can also send different images or forms of drawings that can be digitized with special software and send them by email.