Fax - AbsoluteAstronomy.com

Fax sometimes called telecopying, 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

Bitmap

In computer graphics, a bitmap or pixmap is a type of memory organization or image file format used to store digital images. The term bitmap comes from the computer programming terminology, meaning just a map of bits, a spatially mapped array of bits. Now, along with pixmap, it commonly refers to...

, the information is then transmitted as electrical signals through the telephone system. The receiving fax machine reconverts the coded image, printing a paper copy. Before digital technology became widespread, for many decades, the scanned data was transmitted as analog.

Although businesses usually maintain some kind of fax capability, the technology has faced increasing competition from Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

-based alternatives. Fax machines still retain some advantages, particularly in the transmission of sensitive material which, if sent over the Internet unencrypted, may be vulnerable to interception, without the need for telephone tapping

Telephone tapping

Telephone tapping is the monitoring of telephone and Internet conversations by a third party, often by covert means. The wire tap received its name because, historically, the monitoring connection was an actual electrical tap on the telephone line...

. In some countries, because electronic signature

Electronic signature

An electronic signature, or e-signature, is any electronic means that indicates either that a person adopts the contents of an electronic message, or more broadly that the person who claims to have written a message is the one who wrote it . By comparison, a signature is a stylized script...

s on contracts are not recognized by law while faxed contracts with copies of signatures are, fax machines enjoy continuing support in business.

In many corporate environments, standalone fax machines have been replaced by "fax server

Fax server

A fax server is a system installed in a local area network server that allows computer users whose computers are attached to the LAN to send and receive fax messages...

s" and other computerized systems capable of receiving and storing incoming faxes electronically, and then routing them to users on paper or via an email

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...

(which may be secured). 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.

Wire transmission

Scottish inventor Alexander Bain

Alexander Bain (inventor)

Alexander Bain was a Scottish inventor and engineer who was first to invent and patent the electric clock. Bain installed the railway telegraph lines between Edinburgh and Glasgow.-Early life:...

worked on chemical mechanical fax type devices and in 1846 was able to reproduce graphic signs in laboratory experiments. He received the first fax patent in 1843. Frederick Bakewell

Frederick Bakewell

Frederick Collier Bakewell was an English physicist who improved on the concept of the facsimile machine introduced by Alexander Bain in 1842 and demonstrated a working laboratory version at the 1851 World's Fair in London.-Biography:Born in Wakefield, West Yorkshire, he eventually moved to...

made several improvements on Bain's design and demonstrated telefax machine, the Pantelegraph

Pantelegraph

The pantelegraph was an early form of facsimile machine transmitting over normal telegraph lines developed by Giovanni Caselli, used commercially in the 1860s, that was the first such device to enter practical service, It could transmit handwriting, signatures, or drawings within an area of up to...

, was invented by the Italian physicist Giovanni Caselli

Giovanni Caselli

Giovanni Caselli was an Italian physicist. He is the inventor of the pantelegraph , the predecessor of the modern fax machine...

. He introduced the first commercial telefax service between Paris and Lyon in 1865, some 11 years before the invention of telephone

Telephone

The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

s.

In 1881, English inventor Shelford Bidwell

Shelford Bidwell

Shelford Bidwell was an English physicist and inventor. He is best known for his work with "telephotography", a precursor to the modern fax machine.-Private Life:...

constructed the scanning phototelegraph that was the first telefax machine to scan any two-dimensional original, not requiring manual plotting or drawing. Around 1900, German physicist Arthur Korn

Arthur Korn

Arthur Korn was a German-born physicist, mathematician and inventor, who was of Jewish ancestry...

invented the Bildtelegraph, widespread in continental Europe especially, since a widely noticed transmission of a wanted-person photograph from Paris to London in 1908, used until the wider distribution of the radiofax. Its main competitors were the Bélinograf by Édouard Belin

Édouard Belin

Édouard Belin was born in Vesoul, Haute-Saône on March 5, 1876, and died on March 4, 1963 in Territet .He is the inventor in 1907 of a phototelegraphic apparatus called the Bélinographe, a system able to send remote photographs, via telephone and telegraphic networks...

first, then since the 1930s the Hellschreiber
Hellschreiber
The Hellschreiber or Feldhellschreiber is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on typewriter systems, the Hellschreiber was much simpler and more robust, with only two moving parts...

, invented in 1929 by German inventor Rudolf Hell

Rudolf Hell

Rudolf Hell was a German inventor. He was born in Eggmühl, Germany.From 1919 to 1923 he studied electrical engineering in Munich....

, a pioneer in mechanical image scanning and transmission.

Wireless transmission

As a designer for the Radio Corporation of America (RCA), in 1924, Richard H. Ranger

Richard H. Ranger

Richard Howland Ranger was an American electrical engineer, music engineer and inventor. He was born in Indianapolis, Indiana, the son of John Hilliard and Emily Anthen Gillet Ranger, He served in the U.S. Army Signal Corps during World War I, earning the rank of Major...

invented the wireless photoradiogram, or transoceanic radio facsimile

Radiofax

Radiofax, also known as weatherfax and HF fax , is an analogue mode for transmitting monochrome images. It was the predecessor to slow-scan television...

, the forerunner of today’s "Fax" machines. A photograph of President Calvin Coolidge

Calvin Coolidge

John Calvin Coolidge, Jr. was the 30th President of the United States . A Republican lawyer from Vermont, Coolidge worked his way up the ladder of Massachusetts state politics, eventually becoming governor of that state...

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 to ships at sea. Also in 1924, Herbert E. Ives

Herbert E. Ives

Herbert Eugene Ives was a scientist and engineer who headed the development of facsimile and television systems at AT&T in the first half of the twentieth century. He was also a critic of the special theory of relativity, and attempted to disprove the theory by means of logical arguments and...

of AT&T

AT&T

AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...

transmitted and reconstructed the first color facsimile, using color separations. Around 1952 or so, Finch Facsimile, a highly-developed machine, was described in detail in a book; it apparently was never manufactured in quantity.

In the 1960s, the United States Army transmitted the first photograph via satellite facsimile

Facsimile

A facsimile is a copy or reproduction of an old book, manuscript, map, art print, or other item of historical value that is as true to the original source as possible. It differs from other forms of reproduction by attempting to replicate the source as accurately as possible in terms of scale,...

("fax") to Puerto Rico

Puerto Rico

Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

from the Deal Test Site

Deal Test Site

The Deal Test Site is located in Ocean Township, New Jersey.The Joe Palaia Park was originally started as the Foxburst Farm, a tract which is now the southern portion of the park. It was purchased by Western Electric, , in 1919. The site was later expanded with an additional purchase by AT&T in...

using the Courier satellite

Courier 1B

Courier 1B was the world's first active repeater satellite after launch on 4 October 1960. Courier was built by the Palo Alto, California–based Western Development Labs division of Philco, previously known as Army Fort Monmouth Laboratories and now the Space Systems/Loral division of Loral Space &...

Telephone transmission

Prior to the introduction of the ubiquitous fax machine, one of the first being the Exxon

ExxonMobil

Exxon Mobil Corporation or ExxonMobil, is an American multinational oil and gas corporation. It is a direct descendant of John D. Rockefeller's Standard Oil company, and was formed on November 30, 1999, by the merger of Exxon and Mobil. Its headquarters are in Irving, Texas...

Qwip in the mid-1970s, facsimile machines 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 so that the current in a circuit varied with the amount of light. This current was used to control a tone generator (a modulator), the current determining the frequency of the tone produced. This audio tone was then transmitted using an acoustic coupler

Acoustic coupler

In telecommunications, the term acoustic coupler has the following meanings:# An interface device for coupling electrical signals by acoustical means—usually into and out of a telephone instrument....

(a speaker, in this case) attached to the microphone of a common telephone handset

Handset

On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

. At the receiving end, a handset’s speaker was attached to an acoustic coupler (a microphone), and a demodulator

Fax demodulator

A fax demodulator is a device used to intercept fax messages by listening in on a telephone line or radio signal.A typical fax transmission requires a two-way conversation between two modems . Each modem may be part of a “fax machine” incorporating an image scanner and a printer...

converted the varying tone into a variable current that controlled the 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. Western Union began a "Faxcimile Telegraphy" service in 1935. Their first coast-to-coast message contained images of Mickey Mouse

Mickey Mouse

Mickey Mouse is a cartoon character created in 1928 by Walt Disney and Ub Iwerks at The Walt Disney Studio. Mickey is an anthropomorphic black mouse and typically wears red shorts, large yellow shoes, and white gloves...

Computer facsimile interface

In 1985, Dr. Ayaz Asmat, founder of GammaLink

GammaLink

GammaLink Inc. was founded in Sunnyvale, California by Dr Hank Magnuski and Dr Michael Lutz. The company was the first to invent the PC-to-fax communications technology, GammaFax....

, produced the first computer fax board, called GammaFax

GammaFax

The first personal computer fax board, GammaFax, was produced in 1985 by GammaLink....

Capabilities

There are several different indicators of fax capabilities: Group, class, data transmission rate, and conformance with 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....

(formerly CCITT) recommendations.

Fax machines utilize standard PSTN lines and telephone numbers.

Analogue

Group 1 and 2 faxes are sent in the same manner as a frame of analogue television, with each scanned line transmitted as a continuous analogue signal. Horizontal resolution depended upon the quality of the scanner, transmission line, and the printer. Analogue 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 96 scan line
Scan line
A scan line or scanline is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube display of a television set or computer monitor....

s 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 96 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 ('Basic')
- 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 ('Ultrafine')
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 using ITU-T recommendation T.38 to send digitised images over an IP network using JPEG

JPEG

In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....

compression. T.38 is designed to work with VoIP services and often supported by analog telephone adapters used by legacy fax machines that need to connect through a VoIP service. 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 or more. This type of faxing is not related to 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 2.0 is different from Class 2.
Class 2.1 is an improvement of Class 2.0. Class 2.1 fax devices are referred to as "super G3"; they seem to be a little faster than Class 1/2/2.0.
Class 3 fax devices are responsible for virtually the entire fax session, given little more than a phone number and the text to send (including rendering ASCII text as a raster image). These devices are not common.

Data transmission rate

Several different telephone line modulation techniques are used by fax machines. They are negotiated during the fax-modem

Modem

A modem 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. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

handshake

Handshaking

In information technology, telecommunications, and related fields, 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...

, 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 Phase-shift keying Phase-shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal ....
V.29	1988	9600, 7200, 4800	QAM Quadrature amplitude modulation Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...
V.17	1991	14400, 12000, 9600, 7200	TCM Trellis modulation In telecommunication, trellis modulation is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines...
V.34	1994	28800	QAM Quadrature amplitude modulation Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...
V.34bis	1998	33600	QAM Quadrature amplitude modulation Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...

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
Modified Huffman coding
Modified Huffman coding is used in fax machines to encode black on white images . It combines the variable length codes of Huffman coding with the coding of repetitive data in run-length encoding....

(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 consist 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.

Modified Modified Read

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

Optical resolution

Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.An imaging system may have many individual components including a lens and recording and display components...

of 204×98 (normal) or 204×196 (fine) dots per square inch. The transfer rate is 14.4 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

ITU-T

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

(formerly CCITT) fax group 3 or 4.

The most basic fax mode transfers black and white colors only. The original page is scanned in a resolution of 1728 pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

s/line and 1145 lines/page (for A4). The resulting raw data is compressed

Data compression

In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

using a modified Huffman code

Huffman coding

In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on...

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 preferable 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 printer

Thermal printer

A thermal printer produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image...

s as their printing technology, but since the mid-1990s there has been a transition towards thermal transfer printer

Thermal transfer printer

A thermal transfer printer is a printer which prints on paper by melting a coating of ribbon so that it stays glued to the material on which the print is applied. It contrasts with direct thermal printing where no ribbon is present in the process...

s, inkjet printer

Inkjet printer

An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...

s and laser printers.

One of the advantages of inkjet printing is that inkjets can affordably print in color

Color

Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

; 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 widely supported, so many of the color fax machines can only fax in color to machines from the same manufacturer.

Stroke speed

Stroke speed in facsimile systems, is the rate at which a fixed line perpendicular to the direction of scanning is crossed in one direction by a scanning or recording spot. Stroke speed is usually expressed as a number of strokes per minute. When the fax system scans in both directions, the stroke speed is twice this number. In most conventional 20th century mechanical systems, the stroke speed is equivalent to drum speed.

Fax paper

As a precaution, thermal fax paper is typically not accepted in archives or as documentary evidence in some courts of law unless photocopied. This is because the image-forming coating is eradicable and brittle, and it tends to come off after a long time in storage.

Alternatives

One popular alternative is to subscribe to an internet fax

Internet fax

Internet fax uses the Internet to receive and send faxes.Internet faxing, "e-Fax" or "online faxing" is a general term which refers to sending a document facsimile using the Internet, rather than using only phone networks with a fax machine.Depending on the specific method/implementation ,...

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 TIFF

Tagged Image File Format

TIFF is a file format for storing images, popular among graphic artists, the publishing industry, and both amateur and professional photographers in general. As of 2009, it is under the control of Adobe Systems...

or PDF

Portable Document Format

Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....

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

Health Insurance Portability and Accountability Act

The Health Insurance Portability and Accountability Act of 1996 was enacted by the U.S. Congress and signed by President Bill Clinton in 1996. It was originally sponsored by Sen. Edward Kennedy and Sen. Nancy Kassebaum . Title I of HIPAA protects health insurance coverage for workers and their...

and Gramm–Leach–Bliley Act requirements to keep medical information and financial information private and secure. Utilizing a fax service provider does not require paper, a dedicated fax line, or consumables.

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