Information about Fax

Fax (short for facsimile, from Latin fac simile, "make similar", i.e. "make a copy") is a telecommunications technology used to transfer copies (facsimiles) of documents, especially using affordable devices operating over the telephone network. The word telefax, short for telefacsimile, for "make a copy at a distance", is also used as a synonym. The device is also known as a telecopier in certain industries.

Overview

A "fax machine" usually consists of an image scanner, a modem, and a printer combined into a single package. The scanner converts the content printed on a physical document into a digital image, the modem sends the image data over a phone line to another device, and the printer at the far end produces a copy of the transmitted document.

Some fax machines can be connected to a computer, and the individual components -- the scanner, printer, and occasionally the modem -- can be used independently. Such devices are usually called multifunction printers or MFPs. Fax capabilities are also offered as options for many high-volume workgroup printers and photocopiers.

Although devices for transmitting printed documents electrically have existed, in various forms, since the mid to late 19th century (see "History" below), modern fax machines became feasible only in the mid-1970s as the sophistication increased and cost of the three underlying technologies dropped. Digital fax machines first became popular in Japan, where they had a clear advantage over competing technologies like the teleprinter, since 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.

Although many businesses still maintain some kind of fax capability, the technology has faced increasing competition from Internet-based systems. However, fax machines still retain some advantages, particularly in the transmission of sensitive material which, due to mandates like Sarbanes-Oxley and HIPAA, cannot be sent over the Internet unencrypted. In the UK, because digital signatures on contracts are not recognized by law while faxed contracts with a copies of signatures are, fax machines enjoy continuing popularity in business.

In many corporate environments, standalone fax machines have been replaced by "fax servers" and other computerized systems capable of receiving and storing incoming faxes electronically, and then routing them to users on paper or via secure email. Such systems have the advantage of reducing costs by eliminating unnecessary printouts and reducing the number of inbound analog phone lines needed by an office.

Capabilities

There are several different indicators of fax capabilities: Group, class, data transmission rate, and conformance with ITU-T (formerly CCITT) recommendations.

For those who do not own a fax machine themselves, a fax machine can be contacted by another fax machine with a series of unique numbers (like a telephone number). Fax machines cannot be contacted by home lines or mobiles.

Group

Analog

Group 1 and 2 faxes were sent in the same manner as a frame of analog television, with each scanned line transmitted as a continuous analog signal. Horizontal resolution depended upon the quality of the scanner, transmission line, and the printer. Analog fax machines are obsolete and no longer manufactured. ITU-T Recommendations T.2 and T.3 were withdrawn as obsolete in July 1996.

• 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 are no longer manufactured. Group 2 fax machines can interoperate with Group 3 fax machines.

Digital

Group 3 and 4 faxes are digital formats, and take advantage of digital compression methods to greatly reduce transmission times.

• 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 synchronize). 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.

Fax Over IP (FOIP) Can transmit and receive pre-digitized documents at near realtime speeds. Scanned documents are limited to the amount of time the user takes to load the document in a scanner and for the device to process a digital file. The resolution can vary from as little as 150 DPI to 9600 DPI+. This type of faxing is not like the e-mail to fax service that still uses fax modems at least one way.

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 is T.32.
• Class 2.1 fax devices are referred to as "super G3"; they seem to be a little faster than the other 2 classes.

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.

ITU Standard	Released Date	Data Rates (bit/s)	Modulation Method
V.27	1988	4800, 2400	PSK
V.29	1988	9600, 7200, 4800	QAM
V.17	1991	14400, 12000, 9600, 7200	TCM
V.34	1994	28800	QAM
V.34bis	1998	33600	QAM

Note that 'Super Group 3' faxes use V.34bis modulation that allows a data rate of up to 33.6 kbit/s.

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

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 line scanned 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.

Matsushita Whiteline Skip

A proprietary compression scheme employed on Panasonic fax machines is Matsushita Whiteline Skip (MWS). It can be overlaid on the other compression schemes, but is operative only when two Panasonic machines are communicating with one another. This system detects the blank scanned areas between lines of text, and then compresses several blank scan lines into the data space of a single character.

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 for modems and some fax machines, but fax machines support speeds beginning with 2400 bit/s and typically operate at 9600 bit/s. The transferred image formats are called ITU-T (formerly CCITT) fax group 3 or 4.

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 use the fact that two adjacent scanlines are usually quite similar, saving bandwidth by encoding only the differences.

Fax classes denote the way fax programs interact with fax hardware. Available classes include Class 1, Class 2, Class 2.0 and 2.1, and Intel CAS. Many modems support at least class 1 and often either Class 2 or Class 2.0. Which is preferrable to use depends on factors such as hardware, software, modem firmware, and expected use.

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, inkjet printers and laser printers.

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.

Alternatives

One popular alternative is to subscribe to an internet fax service. Fax service providers allow users to send and receive faxes from their personal computers using an existing email account. No software, fax server or fax machine is needed. Faxes are received as attached .TIF or .PDF files, or in proprietary formats that require the use of the service provider's software. Faxes can be sent or retrieved from anywhere at any time that a user can get internet access. Some services even offer secure faxing to comply with stringent HIPAA and Gramm-Leach-Bliley Act requirements to keep Medical Information and Financial Information private and secure. Utilizing a fax service provider is a very popular option because it requires no paper, toner, fax line, etc. and increases efficiency and productivity in the workplace. Being service-based, there are no maintenance, upkeep or licensing issues to manage, keeping faxing as a simple, easy process.

Another alternative to a physical fax machine is to make use of computer software which allows people to send and receive faxes using their own computers. See Fax server and Unified messaging.

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.

Frederick Bakewell made several improvements on Bain's design and demonstrated the device at the 1851 Great Exhibition in London.

In 1861, the first fax machine, Pantelegraph, was sold by Giovanni Caselli, even before the invention of workable telephones.

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.

An early method for facsimile transmission, the Hellschreiber, was invented in 1929 by Rudolf Hell, a pioneer in mechanical image scanning and transmission.

Prior to the introduction of the now ubiquitous fax machine, one of the first being the Exxon Qwip in the mid-1970s, facsimile machines (the word "fax" had not yet been coined) worked by optical scanning of a document or drawing spinning on a drum. The reflected light, varying in intensity according to the light and dark areas of the document, was focused on a photocell to be converted to an electrical signal varying in frequency. This audio tone was then transmitted using a common telephone handset inserted in an acoustic coupler serving as a modem. At the receiving end, the same technique (handset in acoustic coupler) converted the varying tone into mechanical movement of a pen or pencil to reproduce the image on a blank sheet of paper on an identical drum rotating at the same rate. A pair of these expensive and bulky machines could only be afforded by companies with a serious need to communicate drawings, design sketches or signed documents between distant locations such as an office and factory.

In 1985, Dr. Hank Magnuski, founder of GammaLink, produced the first computer fax board, called GammaFax.

See also

• 3D Fax
• Black fax
• Called Subscriber Identification (CSID)
• Error correction mode (ECM)
• Fax-over-IP T.38
• Fax server
• Faxlore
• Fultograph
• Junk fax
• Telautograph
• Transmitting Subscriber Identification (TSID)

External links

• A Brief History of Facsimile, at HFFAX wireless facsimile site
• The historical evolution of Fax, at technikum29, museum of calculator, computer and communication technology
• World's First Color Fax Machine, article "Tune in a Painting" in 1947 Popular Science
• How Does a fax work?
• Group 3 Facsimile Communication a '97 essay with technical details on compression and error codes, and call establishment and release.
• Scanning & faxing dpi question

Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
..... Click the link for more information.

Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier times telecommunication may have involved the use of
..... Click the link for more information.

facsimile is any copy or reproduction, which bears a close resemblance to the original. The word is mainly used in the context of fax telecommunications technology. A "Facsimile Edition" [1] in publishing is a new edition of an (often classic) book, in the form of an
..... Click the link for more information.

The telephone is a telecommunications device which is used to transmit and receive sound (most commonly speech). Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone.
..... Click the link for more information.

For the taxonomical term, see .

Synonyms (in ancient Greek, συν ("syn") = plus and όνομα ("onoma") = name
..... Click the link for more information.

In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner.
..... Click the link for more information.

Modem (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.
..... Click the link for more information.

A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper transparencies.
..... Click the link for more information.

MFP (Multi Function Printer/Product/Peripheral), multifunctional, all-in-one (AiO), mopier (Multiple Optical coPIER), or Multifunction Device (MFD)
..... Click the link for more information.

A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper transparencies.
..... Click the link for more information.

A photocopier is a machine which makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat.
..... Click the link for more information.

Centuries: 19th century - 20th century - 21st century

1940s 1950s 1960s - 1970s - 1980s 1990s 2000s
1970 1971 1972 1973 1974
1975 1976 1977 1978 1979

- -
- The 1970s decade refers to the years from 1970 to 1979, also called
..... Click the link for more information.

Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.

A teleprinter (teletypewriter, Teletype or TTY for TeleTYpe/TeleTYpewriter) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical
..... Click the link for more information.

input method editor (IME) is a program or operating system component that allows computer users to enter characters and symbols not found on their keyboard. This, for instance, allows the user of a Western keyboard to input Chinese, Japanese, Korean and Indic characters.
..... Click the link for more information.

Origins
Traditional Chinese
Variant characters
Simplified Chinese
Simplified Chinese (2nd-round)
Traditional/Simplified (debate)
Kanji
- Man'yōgana
Hanja
- Idu
Han Tu
- Chữ Nm

..... Click the link for more information.

worldwide view of the subject.
Please [ improve this article] or discuss the issue on the talk page.

This article may contain original research or unverified claims.

Please help Wikipedia by adding references.

..... Click the link for more information.

Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government
..... Click the link for more information.

This article or section may contain original research or unverified claims.

Please help Wikipedia by adding references. See the for details.
This article has been tagged since August 2007.

The Sarbanes-Oxley Act of 2002 (Pub. L.
..... Click the link for more information.

The Health Insurance Portability and Accountability Act (HIPAA) was enacted by the U.S. Congress in 1996.

According to the Centers for Medicare and Medicaid Services (CMS) website, Title I of HIPAA protects health insurance coverage for workers and their families when
..... Click the link for more information.

digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
..... Click the link for more information.

A fax server is a set of software running on a server computer which is equipped with one or more fax-capable modems attached to telephone lines (or, more recently, software modem emulators which use T.38 ("Fax over IP") technology to transmit the signal over an IP network).
..... Click the link for more information.

E-mail (short for electronic mail; often also abbreviated as e-mail, email or simply mail) is a store and forward method of composing, sending, storing, and receiving messages over electronic communication systems.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

Analog television (or analogue television) encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal.
..... Click the link for more information.

scan line is one line, or row, in a raster scanning pattern, such as a video line on a cathode ray tube (CRT) display of a television or computer. A scan line represents a row of picture elements (pixels) in the image being displayed.
..... Click the link for more information.

Modem (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.
..... Click the link for more information.

handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins.
..... Click the link for more information.

This article details the ITU-T V-Series Recommendations for protocols that govern approved modem communication standards and interfaces.

Note: the bis and ter suffixes are ITU-T standard designators of successive iterations of a standard.
..... Click the link for more information.