Teletex was an ITU-T

ITU-T

The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....

 specification for a text and document communications service that could be provided over telephone lines. Teletex allowed for the transmission and routing of Group 4 facsimile

Fax

Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 documents. It was rapidly superseded by e-mail

E-mail

Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

 but the name Teletex lives on in several of the X.500

X.500

X.500 is a series of computer networking standards covering electronic directory services. The X.500 series was developed by ITU-T, formerly known as CCITT, and first approved in 1988. The directory services were developed in order to support the requirements of X.400 electronic mail exchange and...

 standard attributes used in Lightweight Directory Access Protocol

Lightweight Directory Access Protocol

The Lightweight Directory Access Protocol is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol network...

.

Overview

Teletex was designed as an upgrade to the conventional telex service. The terminal-to-terminal communication service of telex would be turned into an office-to-office document transmission system by teletex. Teletex envisaged direct communication between electronic typewriters, word processor

Word processor

A word processor is a computer application used for the production of any sort of printable material....

s and personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s. These units had storage for transmitting and receiving messages. The use of such equipment considerably enhanced the character set available for document preparation.

Character sets

In addition to the standard character set, a rich set of graphic symbols and a comprehensive set of control character

Control character

In computing and telecommunication, a control character or non-printing character is a code point in a character set, that does not in itself represent a written symbol.It is in-band signaling in the context of character encoding....

s were supported in teletex. The set of control characters helped in preparation and reproduction of documents. In particular, they permitted the positioning of the printing element, specification of page orientation, left and right margins, vertical spacing and the use of underlining. The page control feature allowed standard A4 size

ISO 216

ISO 216 specifies international standard paper sizes used in most countries in the world today. It defines the "A" and "B" series of paper sizes, including A4, the most commonly available size...

 papers to be used for receiving messages instead of the continuous stationery

Continuous stationery

Continuous stationery or Continuous form paper is paper which is designed for use with dot-matrix printers and line printers. Other names for continuous stationery include fan-fold paper, sprocket feed paper, burst paper, tractor-feed paper, and pin feed paper...

 used in conventional telex systems.

Transmission and reception

A background/foreground operation was envisaged in teletex. Transmission/reception of messages should proceed in the background without affecting the work which the user might be carrying out in the foreground with the equipment. In other words, a user might be preparing a new document, while another document was being transmitted or received. The teletex would also maintain compatibility with the present telex system and inter-operate with it. Telex procedures called for the exchange of header information

Header (information technology)

In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body....

 before the actual document transfer took place. The header information consisted of four parts:

• Part 1: Destination id,
• Part 2: Originator id,
• Part 3: Date and time stamp,
• Part 4: Document reference.

Twenty four characters were used for source/destination ids, 14 characters for date and time stamp, and 7 characters for document reference which also specified the number of pages in the document. Destination/source id consisted of four fields

Field (computer science)

In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns....

:

• Field 1: Country/Network code,
• Field 2: National subscriber number,
• Field 3: Reserved for future use,
• Field 4: Terminal/Owner code.

The number of characters allotted to each of the above fields was variable, subject to a maximum for each field, the total being 24 characters.

External links

• Connected Earth website