edVirtus Reference

What Is Telex?

How Did Telex Provide Worldwide Text Communication Before Email?

Telex was an international switched communication network that enabled users to exchange typed text messages directly between teleprinters. Widely used from the mid-twentieth century until the rise of email and the Internet, Telex provided reliable written communication for businesses, governments, shipping companies, airlines, banks, and news organisations around the world.

The basic principle is straightforward. Each Telex terminal consisted of a keyboard and a printer. When a user typed a message, each keystroke was converted into a standard digital character code and transmitted through the Telex network to a remote terminal, where the characters were printed automatically as they were received. The system established a dedicated circuit between the two terminals for the duration of the communication, much like a telephone call.

A useful analogy is a typewriter connected directly to another typewriter anywhere in the world. Every key pressed on one machine immediately caused the corresponding character to be printed on the other, allowing two users to exchange written messages in real time.

Telex networks employed circuit switching, using many of the same switching principles as the Public Switched Telephone Network (PSTN). Each subscriber was assigned a unique Telex number, allowing messages to be sent automatically to any other subscriber connected to the international network. Most systems used the International Telegraph Alphabet No. 2 (ITA2), also known as the Baudot code, a five-bit character encoding designed specifically for teleprinter communication.

One of Telex's greatest strengths was its reliability and legal acceptance. Because messages were printed directly at the receiving terminal and included details such as the sender's identity, many organisations regarded Telex messages as official business correspondence. The network became particularly important for international commerce, diplomatic communication, aviation, maritime operations, and financial transactions long before electronic mail became available.

It is important to distinguish Telex from teleprinter. A teleprinter is the terminal device used to type and print messages, whereas Telex is the switched communication network that interconnects those terminals. Likewise, Telex differs from email. Telex establishes a dedicated real-time communication circuit between two terminals, while email stores digital messages on computer servers for later retrieval without requiring both parties to be connected simultaneously.

Today, Telex has been almost entirely replaced by email, secure Internet messaging, and electronic data interchange (EDI). Nevertheless, it represented one of the earliest forms of global digital communication and introduced many concepts that remain familiar today, including unique network addresses, automatic message routing, international communication standards, and electronically transmitted written correspondence. Telex played a pivotal role in the evolution of modern telecommunications and laid important foundations for today's digital communication networks.