Telex vs. Fax

Main Difference

The main difference between Telex and Fax is that the Telex is a switched network of teleprinters and Fax is a method of transmitting images, often of documents.

• Telex

  The telex network was a public switched network of teleprinters similar to a telephone network, for the purposes of sending text-based messages. Telex was a major method of sending written messages electronically between businesses in the post-World War II period. Its usage went into decline as the fax machine grew in popularity in the 1980s.

  The “telex” term refers to the network, not the teleprinters; point-to-point teleprinter systems had been in use long before telex exchanges were built in the 1930s. Teleprinters evolved from telegraph systems, and, like the telegraph, they used binary signals, which means that symbols were represented by the presence or absence of a pre-defined level of electric current. This is significantly different from the analog telephone system, which used varying voltages to represent sound. For this reason, telex exchanges were entirely separate from the telephone system, with their own signalling standards, exchanges and system of “telex numbers” (the counterpart of telephone numbers).

  Telex provided the first common medium for international record communications using standard signalling techniques and operating criteria as specified by the International Telecommunication Union. Customers on any telex exchange could deliver messages to any other, around the world. To lower line usage, telex messages were normally first encoded onto paper tape and then read into the line as quickly as possible. The system normally delivered information at 50 baud or approximately 66 words per minute, encoded using the International Telegraph Alphabet No. 2. In the last days of the telex networks, end-user equipment was often replaced by modems and phone lines, reducing the telex network to what was effectively a directory service running on the phone network.

• Fax

  Fax (short for facsimile), sometimes called telecopying or telefax (the latter short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other output device. The original document is scanned with a fax machine (or a telecopier), which processes the contents (text or images) as a single fixed graphic image, converting it into a bitmap, and then transmitting it through the telephone system in the form of audio-frequency tones. The receiving fax machine interprets the tones and reconstructs the image, printing a paper copy. Early systems used direct conversions of image darkness to audio tone in a continuous or analog manner. Since the 1980s, most machines modulate the transmitted audio frequencies using a digital representation of the page which is compressed to quickly transmit areas which are all-white or all-black.

• Telex (noun)

  an international system of telegraphy with printed messages transmitted and received by teleprinters using the public telecommunications network

  “networks can be set up to send and receive text by telex”

  “telex messages”

• Telex (noun)

  a device used for telex

  “I found it waiting on the telex in Mitch’s office”

• Telex (noun)

  a message sent by telex

  “I received your telex yesterday”

• Telex (verb)

  communicate with (someone) by telex

  “he had telexed Ms Starnes from Zurich”

• Telex (verb)

  send (a message) by telex

  “telexing a 70 page document is a time-consuming process”