Teletex System | Abandoned 20th Century Technology

This post is about the teletex system and should not be confused with teletext, which is a standard for displaying text and basic graphics on suitably equipped televisions. Also, it is not to be confused with telex, which is briefly discussed in the last paragraph of this post.

Some Examples of Teletex Terminals

IBM PS/2 teletex terminal. — IBM PS/2 teletex system terminal

Olivetti M24 teletex system terminal. — Olivetti M24 teletex system terminal

Sagem TCX2000 teletex system terminal. — SAGEM TCX2000 teletex system terminal

First image attribution: Federigo Federighi, CC BY-SA 4.0 via Wikimedia Commons. Second image attribution: Hinnerk11, CC BY-SA 4.0 via Wikimedia Commons. Derivative version is greyscaled. Third image: Jvjvjvjv, CC BY-SA 3.0 via Wikimedia Commons.

Scope of This Post

I did not use a teletex system, but as a telex operator, I knew it was available to UK subscribers from the mid-1980s to the early 1990s.

Information about teletex on the internet is limited, and the Wikipedia article is brief and lacks detail. I had to delve deep into the internet to find out more. There may be errors in my post, and I welcome your thoughts in the comments section at the foot of this post.

Research For This Article

What I found on the internet were quite a few snippets of information about the teletex system, but no single document that could explain this system in the detail I wanted for this post. I did find one excellent video by Harald Welte at RetroNetCall titled “Teletex: The brief abandoned step between Telex and Telefax.”

The video’s author also did not use teletex firsthand and compiled the video through extensive online research, which I partly used for this post.

Watch The Video

The brief abandoned step between Telex and Telefax.

Background and Intended Use of Teletex

Teletex is an obsolete communications system with parameters set by the ITU-T*. Teletex was a higher-specification document transmission system than telex. It was intended to serve as a bridge between email and fax.

*ITU-T. International Telecommunication Union Telecommunication Standardisation Sector.

The teletex system existed in Germany (only in West Germany) between 1981 and 1996. The system was also used in Austria, Denmark, Belgium, Finland, France, the Netherlands, South Africa, Switzerland, Turkey, the UK and the USA. Source: RetroNetCall’s video referenced above. I am unable to ascertain the start and end dates of teletex in the additional countries mentioned above. I imagine the dates were broadly in line with those in Germany.

Teletex could exchange documents that included more complex layouts, exceeding the capabilities of telex. Unlike telex, which was restricted to a basic character set and could not display graphics, teletex allowed for the transmission of documents with richer formatting and structure.

Restricted character set of teleprinters. — Restricted character set of teleprinters

Above Image attribution: User: Huestones with derivative work by User: TedColes, CC BY-SA 3.0, via Wikimedia Commons.

In some companies during the 1980s, fax machines were limited to Group 1 and Group 2 standards. Group 1 faxes took about 6 minutes per page and Group 2 about 3 minutes per page, often producing low-quality copies. I used a Group 1 fax machine in the 1980s, which was notably large. In contrast, teletex offered much faster transmission and better document fidelity than these early fax models.

What You Could Do With a Teletex Terminal

Use the terminal as an ordinary electronic typewriter.
Print documents with a connection to a separate printer.
Send and receive documents to and from any teletex terminal worldwide.
Send and receive telex messages to a teleprinter terminal as long as that teleprinter was connected to a public switched telex network and the character set used was compatible with the restricted character set limitations that a teleprinter could handle, in accordance with the International Telegraph Alphabet No. 2. Documents intended for a telex recipient needed have a line length restricted to 69 characters, which is the maximum line length most telex terminals could handle*.

*TWX teleprinters, such as the Teletype Model 33 in North America, were capable of a maximum line length of 74 characters. Source: Teletype Model 33 ASR. While I have not found any documents on the internet to prove otherwise, I would imagine that when sending documents from the Teletype Model 33 to most other teleprinters (which I believe were the majority of teleprinters worldwide), the operator would have to ensure, or should have ensured, that the character line length did not exceed 69 characters, to prevent over-printing at the end of lines.

Teletex Was Much Faster Than Telex

Teletex terminals could send messages at much higher speeds than telex machines could. The transmission speed was 2,400 bits/sec, around thirty times faster than telex. Source: Information Technology Impact on the way of life. PDF file. Page 30.

Teletex System Specifications

Here is a link to a PDF file on ITU-T’s website that details the equipment specifications for using the teletex service. The link will automatically open a PDF file on your computer or other device.

Complete Listing of ITU-T Teletex System Specifications

F.200, T.60, T.61, T.62, and T.70. Source: Teletex: The brief abandoned step between Telex and Telefax. Fast-forward the video to 5 minutes and 20 seconds to view that portion.

If you would like to view each of these PDF documents, you can visit the ITU-T’s website Home Page and use their search facility by typing in one of the document specification numbers listed above.

Why Was The Teletex System Abandoned

At the time of the initial concept for the teletex system in the early 1980s, commercial electronic mail had already been developed. It was being used by many companies worldwide. Source: Personal experience of the author in office environments. Group 3 and Group 4 fax machines were established in 1980 and 1984, respectively. Source: Fax Communications at Britannica. I found that these digital fax machines could send a page of A4 text in under 1 minute.

Crucially, however, in the 1990s, private email had already taken hold among home users and was rapidly gaining popularity within commercial enterprises. This popularity and accessibility of email must have signalled the end not only for the teletex system but also for the worldwide telex network.