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An example of a modern fax machine.

Fax (short for facsimile - from Latin "fac simile", "make similar", i.e. "make a copy" - or telefacsimile) is a telecommunications technology used to transfer copies of documents, especially using affordable devices operating over the telephone network. The words telecopy and telefax are also used as synonyms. Image File history File links Please see the file description page for further information. ... This page is a candidate to be moved to Wiktionary. ... Latin is an ancient Indo-European language originally spoken in the region around Rome called Latium. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ... Look up Synonym in Wiktionary, the free dictionary. ...

Overview

A fax machine is essentially an image scanner, a modem, and a computer printer combined into a highly specialized package. The scanner converts the content of a physical document into a digital image, the modem sends the image data over a phone line, and the printer at the other end makes a duplicate of the original document. CanoScan9950F Desktop scanner, with the lid raised. ... A modem (a portmanteau constructed from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Fax machines with additional electronic features can connect to computers, can be used to scan documents into a computer, and to print documents from the computer. Such high-end devices are called multifunction printers and cost more than fax machines. Multifunction printer A multifunctional printer An MFP (Multi Function Printer/Product/Peripheral), multifunctional, all-in-one (AiO), or mopier or Multifunction Device (MFD), is an office machine that includes the following functionality in one physical body, so as to have a smaller footprint in a home or small-business setting...

Although fax machines of some sort or another have existed since the mid-late 19th century (see "History" below), modern fax technology became feasible only in the mid-1970s as the sophistication and cost of the three underlying technologies improved to a reasonable level. Fax machines first became popular in Japan, where they had a clear advantage over competing technologies like the teleprinter; at the time, before the development of easy-to-use input method editors, it was faster to handwrite kanji than to type the characters. Over time, faxing gradually became affordable, and by the mid-1980s, fax machines were very popular around the world. The 1970s decade refers to the years from 1970 to 1979, inclusive. ... Teletype machines in World War II A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ... An IME for inputting Japanese characters in Mac OS 9 An input method editor (IME) is a program or operating system component that allows computer users to enter complex characters and symbols (such as Chinese, Japanese, Korean and Tibetan characters), using a standard Western keyboard. ... Japanese writing Kanji 漢字 Kana 仮名 Hiragana 平仮名 Katakana 片仮名 Manyogana 万葉仮名 Uses Furigana 振り仮名 Okurigana 送り仮名 Rōmaji ローマ字 Kanji (Japanese: ) are the Chinese characters that are used in the modern Japanese logographic writing system along with hiragana (平仮名), katakana (片仮名), arabic numerals, and the Roman alphabet. ... The 1980s decade refers to the years from 1980 to 1989, inclusive. ...

However, although most businesses still maintain some kind of fax capability, the technology appears increasingly dated in the world of the Internet.

Capabilities

There are several different indicators of fax capabilities: Group, class, data transmission rate, and conformance with ITU-T (formerly CCITT) recommendations. The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... ITU-T is the telecom standardization organization of the International Telecommunication Union (ITU). ...

Group

• Group 1 faxes conform to the ITU-T Recommendation T.2. Group 1 faxes take six minutes to transmit a single page, with a vertical resolution of 98 scan lines per inch. Group 1 fax machines are obsolete and no longer manufactured.
• Group 2 faxes conform to the ITU-T Recommendations T.30 and T.3. Group 2 faxes take three minutes to transmit a single page, with a vertical resolution of 100 scan lines per inch. Group 2 fax machines are almost obsolete, and not manufactured. Group 2 fax machines can interoperate with Group 3 fax machines.
• Group 3 faxes conform to the ITU-T Recommendations T.30 and T.4. Group 3 faxes take between six and fifteen seconds to transmit a single page (not including the initial time for the fax machines to handshake and synchronise). The horizontal and vertical resolutions are allowed by the T.4 standard to vary among a set of fixed resolutions:
  • Horizontal: 100 scan lines per inch
    • Vertical: 100 scan lines per inch
  • Horizontal: 200 or 204 scan lines per inch
    • Vertical: 100 or 98 scan lines per inch ('Standard')
    • Vertical: 200 or 196 scan lines per inch ('Fine')
    • Vertical: 400 or 391 (note not 392) scan lines per inch ('Superfine')
  • Horizontal: 300 scan lines per inch
    • Vertical: 300 scan lines per inch
  • Horizontal: 400 or 408 scan lines per inch
    • Vertical: 400 or 391 scan lines per inch
• Group 4 faxes conform to the ITU-T Recommendations T.563, T.503, T.521, T.6, T.62, T.70, T.72, T.411 to T.417. They are designed to operate over 64 kbit/s digital ISDN circuits. Their resolution is determined by the T.6 recommendation, which is a superset of the T.4 recommendation.

Class

Computer modems are often designated by a particular fax class, which indicates how much processing is offloaded from the computer's cpu to the fax modem.

• Class 1 fax devices do fax data transfer where the T.4/T.6 data compression and T.30 session management are performed by software on a controlling computer. This is described in ITU-T recommendation T.31.
• Class 2 fax devices perform T.30 session management themselves, but the T.4/T.6 data compression is performed by software on a controlling computer. The relevant ITU-T recommendation T.32.

Data transmission rate

Several different telephone line modulation techniques are used by fax machines. They are negotiated during the fax-modem handshake, and the fax devices will use the highest data rate that both fax devices support, usually a minimum of 14.4 kbit/s for Group 3 fax. A modem (a portmanteau constructed from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... In telecommunication and microprocessor systems, the term handshaking has the following meanings: In data communications, a sequence of events governed by hardware or software, requiring mutual agreement of the state of the operational modes prior to information exchange. ...

Note that 'Super Group 3' faxes use V.34bis modulation that allows a data rate of up to 33.6 kbit/s. Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). ... Quadrature amplitude modulation (QAM) is a modulation scheme which conveys data by changing (modulating) the amplitude of two carrier waves. ... In telecommunication, trellis modulation (also known as trellis coded modulation, or simply TCM) is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines. ... Quadrature amplitude modulation (QAM) is a modulation scheme which conveys data by changing (modulating) the amplitude of two carrier waves. ... V.34bis, also known as V.34plus is an ITU-T recommendation for a modem, building on the V.34 standard but allowing up to 33. ...

Compression

As well as specifying the resolution (and allowable physical size of the image being faxed), the ITU-T T.4 recommendation specifies two compression methods for decreasing the amount of data that needs to be transmitted between the fax machines to transfer the image. The two methods are:

• Modified Huffman (MH), and
• Modified READ (MR)

Modified Huffman coding is used in fax machines to encode black on white images (bitmaps). ...

Modified Huffman

Modified Huffman (MH) is a codebook-based run-length encoding scheme optimised to efficiently compress whitespace. As most faxes consists mostly of white space, this minimises the transmission time of most faxes. Each scanned line is compressed independently of its predecessor and successor.

Modified Read

Modified Read (MR) encodes the first scanned line using MH. The next line is compared to the first, the differences determined, and then the differences are encoded and transmitted. This is effective as most lines differ little from their predecessor. This is not continued to the end of the fax transmission, but only for a limited number of lines until the process is reset and a new 'first line' encoded with MH is produced. This limited number of lines is to prevent errors propagating throughout the whole fax, as the standard does not provide for error-correction. MR is an optional facility, and some fax machines do not use MR in order to minimise the amount of computation required by the machine. The limited number of lines is two for 'Standard' resolution faxes, and four for 'Fine' resolution faxes.

The ITU-T T.6 recommendation adds a further compression type of Modified Modified READ (MMR), which simply allows for a greater number of lines to be coded by MR than in T.4. This is because T.6 makes the assumption that the transmission is over a circuit with a low number of line errors such as digital ISDN. In this case, there is no maximum number of lines for which the differences are encoded.

Typical characteristics

Group 3 fax machines transfer one or a few printed or handwritten pages per minute in black-and-white (bitonal) at a resolution of 100x200 or 200x200 dots per inch. The transfer rate is 14.4 kilobits per second (kbit/s) or higher (but fax machines support speeds beginning with 2400 bit/s). The transferred image formats are called ITU-T (formerly CCITT) fax group 3 or 4. The word resolution has several meanings, depending on context. ... A bit refers to a digit in the binary numeral system (base 2). ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ...

The most basic fax mode transfers black and white only. The original page is scanned in a resolution of 1728 pixels/line and 1145 lines/page (for A4). The resulting raw data is compressed using a modified Huffman code optimized for written text, achieving average compression factors of around 20. Typically a page needs 10 s for transmission, instead of about 3 minutes for the same uncompressed raw data of 1728×1145 bits at a speed of 9600 bit/s. The compression method uses a Huffman codebook for run lengths of black and white runs in a single scanned line, and it can also uses the fact that two adjacent scanlines are usually quite similar, saving bandwidth by encoding only the differences. This example shows an image with a portion greatly enlarged. ... A comparison of different paper sizes A4 is a standard paper size, defined by the international standard ISO 216 as 210×297 mm (roughly 8. ... In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ... In computer science, Huffman coding is an entropy encoding algorithm used for lossless data compression. ...

There are different fax classes, including Class 1, Class 2 and Intel CAS.

Fax machines from the 1970s to the 1990s often used direct thermal printers as their printing technology, but since the mid-1990s there has been a transition towards thermal transfer printers and inkjet printers. Direct thermal printers create an image by selectively heating coated paper when the paper passes over the thermal print head. ... Thermal transfer Barcode Printers Barcode Printers typically come in fixed sizes of 4 inches, 6 inches or 8 inches wide. ... Inkjet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper. ...

One of the advantages of inkjet printing is that inkjets can affordably print in color; therefore, many of the inkjet-based fax machines claim to have color fax capability. There is a standard called ITU-T30e for faxing in color; unfortunately, it is not yet widely supported, so many of the color fax machines can only fax in color to machines from the same manufacturer. Color is an important part of the visual arts. ...

Alternatives

A modern alternative for sending a fax is sending an email with one or more image files as attachments. This allows colour and is more versatile with respect to resolution. See Internet fax E-mail, or email, is short for electronic mail and is a method of composing, sending, and receiving messages over electronic communication systems. ... For images in Wikipedia, see Wikipedia:Images. ... A computer file is a collection of information that is stored in a computer system and can be identified by its full path name. ... The term attachment has multiple meanings: An email attachment Psychological attachment: see Attachment theory Attachment as a vice in Buddhism; see Buddhism This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Internet fax uses the internet to receive and send faxes. ...

At the receiving end, much research has occurred into how to more efficiently process incoming faxes, now that digital storage is much cheaper than it was in the 1970s, and junk faxes have become a common problem (and an enormous waste of paper). Junk faxes are unsolicited advertising via fax transmission. ...

Some high-end communications servers do not automatically print out all incoming faxes, but instead integrate them into a single in-box along with other forms of store and forward communications like email and voice mail (see unified messaging). Store and forward is a communications technique in which messages are sent to a intermediate station where they are kept and sent at a later time to the final destination or to another intermediate station. ... Voicemail (or voice mail; abbreviated v-mail or vmail) is a specific application of an interactive voice response system. ... Unified Messaging (or UM) is the integration of different streams of messages (email, Fax, voice, video, etc. ...

History

Scottish inventor Alexander Bain is often credited with the first fax patent in 1843. He used his knowledge of electric clock pendulums to produce a back-and-forth line-by-line scanning mechanism. Alexander Bain (October 1811 – January 2, 1877), was a clockmaker who invented an electric clock, the electric printing telegraph and the first fax machine. ... 1843 was a common year starting on Sunday (see link for calendar). ... An analog wall clock A clock (from the Latin cloca, bell) is an instrument for measuring time and for measuring time intervals of less than a day—as opposed to a calendar. ... Simple gravity pendulum assumes no air resistance and no friction of/at the nail/screw. ...

In 1861 the first fax machine, Pantelegraph, was sold by Giovanni Caselli, even before the invention of workable telephones. 1861 is a common year starting on Tuesday. ... The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ...

As a designer for the Radio Corporation of America (RCA), in 1924, Richard H. Ranger invented the wireless photoradiogram, or transoceanic radio facsimile, the forerunner of today’s "Fax" machines. A photograph of President Calvin Coolidge sent from New York to London on November 29, 1924 became the first photo picture reproduced by transoceanic radio facsimile. Commercial use of Ranger’s product began two years later. Radio fax is still in common use today for transmitting weather charts and information. RCA, formerly an initialism for the Radio Corporation of America, is now a trademark used by two companies for products descended from that common ancestor: Thomson Consumer Electronics, which manufactures RCA-branded televisions, DVD players, video cassette recorders, direct broadcast satellite decoders, camcorders, audio equipment, telephones, and related accessories; and... Richard Howland Ranger (1899-1961) was an American electrical engineer and inventor. ... A weather map received via radiofax, from the Bureau of Meteorology, 5100 kHz, WMC (Charleville). ... John Calvin Coolidge, Jr. ... November 29 is the 333rd (in leap years the 334th) day of the year in the Gregorian Calendar. ... 1924 (MCMXXIV) was a leap year starting on Tuesday (link will take you to calendar). ...

An early method for facsimile transmission, the Hellschreiber, was invented in 1929 by Rudolf Hell, a pioneer in mechanical image scanning and transmission. The Hellschreiber or Feldhellschreiber was a facsimile-based teleprinter invented by Rudolf Hell. ... 1929 (MCMXXIX) was a common year starting on Tuesday (link will take you to calendar). ... Rudolf Hell (December 19, 1901 – March 11, 2002) was a German inventor. ...

In 1985 Dr Hank Magnuski, founder of GammaLink, produced the first computer fax board, called GammaFax. This article is about the year. ... Prior to founding NCast, Dr. Hank Magnuski was cofounder and CEO of GammaLink. ... GammaLink Inc. ... The first computer fax board, GammaFax, was produced in 1985 by GammaLink. ...

See also

• error correction mode (ECM)
• telautograph
• MyFax
• WinFax
• Faxmail for windows

Error correction mode (ECM) is an optional transmission mode built into Class 1 fax machines or fax modems. ... The telautograph is an analog precursor to the modern fax machine. ... WinFax is a Windows-based software product designed to let computers equipped with fax-modems to communicate directly to stand-alone fax machines, or other similarly-equipped computers. ... FaxMail for Windows is a Windows program that allows computers to receive and transmit faxes to and from fax machines and other computers with fax software. ...

External links

• A Brief History of Facsimile
• What is Fax and History of Fax
• FAQ: How can I send a fax from the Internet?
• Death of the Fax Machine!
• Stupidity of Faxing
• Group 3 Facsimile Communication a '97 essay with technical details on compression and error codes, and call establishment and release.
• World's First Color Fax Machine