Sunday, August 23, 2009

Wire transmission

Scottish inventor Alexander Bain worked on chemical mechanical facsimile type devices and in 1846 was able to reproduce graphic signs in lab experiments. Frederick Bakewell made several improvements on Bain's design and demonstrated his device at the 1851 Great Exhibition in London. Bain and Bakewell's systems were inferior and could reproduce only poor quality images. They lacked synchronization between the transmitting mechanism and the receiving mechanism. In 1861, the first practical operational electro-mechanical commercially exploited telefax machine, the Pantelegraph, was invented by the Italian physicist Giovanni Caselli. He introduced the first commercial telefax service between Paris and Lyon some 11 years before the invention of workable telephones.[1][2]
In 1881, English inventor Shelford Bidwell constructed the scanning phototelegraph that was the first telefax machine to scan any two-dimensional original, not requiring manual plotting or drawing anymore. Around 1900, German physicist Arthur Korn 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 first, then since the 1930s the Hellschreiber, invented in 1929 by Rudolf Hell, a pioneer in mechanical image scanning and transmission

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 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 (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 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 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.

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.

.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
4800, 2400
9600, 7200, 4800
14400, 12000, 9600, 7200
Note that 'Super Group 3' faxes use V.34bis modulation that allows a data rate of up to 33.6 kbit/s.


A "fax machine" usually consists of an image scanner, a modem, and a printer.
Although devices for transmitting printed documents electrically have existed, in various forms, since the 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[citation needed]. In some countries, because electronic signatures 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 servers" and other computerized systems capable of receiving and storing incoming faxes electronically, and then routing them to users on paper or via an email (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.


FFax (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. Although fax is not an acronym, it is often written as “FAX”. The device is also known as a telecopier in certain industries. When sending documents to people at large distances, faxes have a distinct advantage over postal mail in that the delivery is nearly instantaneous, yet its disadvantages in quality have relegated it to a position beneath email as the prevailing form of electronic document transfer.

Saturday, August 22, 2009

What is a FAX?

The transmission of photographs, drawings, maps, and written or printed words by electric signals. Light waves reflected from an image are converted into electric signals, transmitted by wire or radio to a distant receiver, and reconstituted on paper or film into a copy of the original.
Facsimile is used by news services to send news and photos to newspapers and television stations, by banks, airlines, and railroads to transmit the content of documents, and by many other businesses as an aid in data handling and record keeping.
Facsimile systems involve optical scanning, signal encoding, modulation, signal transmission, demodulation, decoding, and copy making.
Scanning is done in a manner similar to that used in television. An original, a photo for example, is illuminated and systematically examined in small adjacent areas called pixels (picture elements). Light reflected from each pixel is converted into electric current by an electronic device, a photocell, photodiode, or charge-coupled device (CCD).
A single such device may be used to cover one pixel after another in a row, row after row from top to bottom until the entire image has been translated into electric impulses. This is rectilinear scanning. Scanning may also be done a row at a time by a battery of devices; this is array scanning.
In multispot scanning, a vertical array of photodevices moves across the image, examining the pixels column by column. As the array passes down the copy, it produces a set of current pulses from each photodevice. The separate currents, however produced, are then transmitted successively over a single circuit to the distant receiver.
To secure fine detail in the reproduced image it is necessary to use very small pixels. In one standard, Group 3 of the International Telegraph and Telephone Consultative Committee ( CCITT ), each pixel is a rectangle 0.12 by 0.13 mm ( 1 inch=25.4 mm ). On this standard, subject copy measuring 8 by 11 inches ( 20 x 28 cm ) is divided into 3.6 million pixels.
This compares with about 200,000 pixels for televised images. The pixels used in high-resolution facsimile systems have dimensions one-fifth those of the CCITT standard mentioned above, whereas in low-definition systems the dimensions may be twice as great.
The image may be illuminated as in rectilinear scanning, or a relatively large area of the image may be illuminated, the photodevice viewing the image through a lens aperture that restricts its field to a single pixel at a time.
In a commonly used facsimile scanning system ( invented by Frederick Bakewell in 1848 and based on Alexander Bain's work of 1842 ) the subject copy is wrapped around a drum. A finely focused spot of light falls on the copy and the light reflected from that pixel is picked up by the photodevice. The drum is rotated so that the light spot traces a line across the copy, examining each pixel in turn.
As the drum rotates, the light source is moved slowly on a carriage parallel to the drum axis, tracing out a spiral of adjacent lines until the entire area of the copy has been scanned. At least once in each rotation of the drum a signal transmitted to the recorder keeps the scanner and the recorder in step.
In drum scanning, the copy may also be illuminated broadly and examined by a photodevice fitted with a lens aperture.
Copy cannot always be conveniently wrapped around a drum. In such cases, flat copy may be scanned by a spot of light directed across its surface by a moving mirror. Mirror scanning may also be used when the copy is wrapped on a drum, or while it is being pulled from a roller. Laser light produces a very fine beam that travels across the copy, row by row, as the copy moves vertically.
In one arrangement the mirror is rocked back and forth, moving the beam across the copy. In another, a rotating polygonal mirror is used. This mirror typically has 18 flat mirror surfaces on its periphery, each capable of scanning a row of pixels.
Very fast scanning can be achieved by rapid rotation of the mirror and corresponding vertical motion of the copy. The beam is reflected from each pixel into a photodevice that converts successive light values into corresponding currents. Electronic scanning of flat copy may also be done by arrays of photodiodes or charge-coupled devices.
For scanning rates higher than about 6 rows per second laser beams with polygonal mirrors and arrays of photodevices are favored.

Breakthrough at last

The Japanese state telecom was the pioneer in opening its lines to public fax machines - not surprisingly, considering the advantages that the fax machine offers for transmitting text in a language with as many letters as Japanese, a nightmare to write on a teleprinter. The Japanese were drawing the practical conclusions of what the Chinese emperor had realized almost a century earlier. This was the start of the brief but intense heyday of the fax, which has radically changed our ways of communicating, only to be progressively replaced by direct communication between computers.It is intriguing to speculate about the enormous consequences for business and news services, not to mention homes, that an early breakthrough for Caselli's pantelegraph might have had. With telephone lines already spanning the world, the technology for the fax revolution was in place one hundred years ago. So it is not too far-fetched, after all, to imagine Queen Victoria faxing off her order for Scottish salmon!

Modest progress

The fax made progress nevertheless. Dr Arthur Korn, a German scientist, invented the principle of photoelectric reading in 1902. By 1910 newspapers were regularly sending and receiving pictures between major cities in Europe. In 1922, Dr Korn managed to transmit images between Europe and the U.S. by radio. In the U.S. of the Roaring Twenties, the fax was expected to become a common household appliance and millions of dollars were spent on developing it. However, the anticipated breakthrough did not occur, and it was not until the 1960s that the fax machine spread from the offices of the leading newspapers to become a familiar item of equipment in other business sectors.Electronics companies, meanwhile, were preoccupied with other, seemingly more glamorous, inventions, such as television, and it was some time before fax machines became mutually compatible and reasonably priced. In 1970, there were no more than 50,000 facsimile machines in the entire USA. But by 1948, the AT&T fax system could be incorporated in a desktop fax and transmit a 15 x 20 cm photograph in seven minutes.

Fax machine commercialized

However, it is a far cry from merely demonstrating a device at an exhibition to making it into a commercial success. The honor of designing the first fax service in actual use goes to Giovanni Caselli, an Italian abbot, born in Siena in 1815, who turned his hand to science and was, by 1849, editing a scientific magazine. In 1856 he claimed that he had developed a device, which he called a "pantelegraph," that could send facsimiles of images and text.Caselli received enthusiastic support from the French emperor, Napoleon III, who personally visited Caselli's workshop in 1860. He ensured that Caselli had access to the telegraph lines he needed, and a commercial fax service was inaugurated in Paris in 1865. It transmitted pictures and text between major French cities for some five years. A Pantelegraph Society was also founded in order to promote the new invention, which attracted extensive and enthusiastic press coverage at the time. When Caselli succeeded in opening a regularly working fax connection between Paris and Lyons, he was awarded the Cross of the Legion of Honor by Napoleon III. There still exist fully legible copies of letters sent by facsimile during this period, and a few contemporary facsimile machines are displayed in French museums.After Caselli's fax service achieved worldwide renown in the 1860s, he was invited by King Victor Emmanuel of Italy to demonstrate the fax machine at a world exhibition in Turin. He also made successful experimental fax transmissions between London and Manchester, and a company was founded to start regular services. However, it was swept away by the bank crisis of 1864

Space Meteorology History

Meterology is the focus of many scientists all over the world, meteorology forecasts were not available on mass to the general public until H.C. Russell, New South Wales Government Astronomer and Meteorologist from 1870 to 1905, produced Australia's first newspaper weather map in 1877.Space meteorology on the other hand had its origins in the early 1950s. It was not until the 1st of April 1960, that the TIROS-I (Television Infrared Operational Satellite) the world's first meteorological satellite was launched. The first direct picture transmission took place on 21st December 1963 by TIROS-VIII. The World Weather Watch (WWW) and Global Atmospheric Research Program (GARP) were established worldwide.The WWW developed as an international collaborative system for global weather observation by satellite and by conventional means.The Global Research Program initiated a series of innovative developments in meteorological satellite technology during the 1960s and 1970s.The First GARP Global Experiment (FGGE) of 1979 provided the first global view of the earth's atmosphere, essential to the provision of medium-range forecasts, and essential to the understanding of the meteorological processes, which govern the evolution of climate.The spin-scan camera on board the Applications Technology Satellite ATS-1 provided near-continuous photo coverage of the earth and its cloud cover. This was the first weather satellite in a geostationary orbit, launched 6 December 1966.Three years later the first detailed quantitative measurements by satellite of the temperature and moisture of the atmosphere at various levels were obtained.

1898 Hummel's Telediagraph

The Telediagraph was one of several early fax-like devices sending pictures via telegraph lines. It was invented circa 1895 by Ernest A. Hummel, a watchmaker of St. Paul, Minnesota. The first machines were installed in the office of the New York Herald in 1898. By 1899, Hummel had improved the machine and the newspaper had machines in the offices ofthe Chicago Times Herald, the St. Louis Republic, the Boston Herald, and the Philadelphia Inquirer.The system used synchronised rotating 8-inch drums, with a platinum stylus used as an electrode in the transmitter. The original image was drawn on 8x6" tin-foil using a non-conducting ink made from shellac mixed with alcohol. The image was received on carbon paper wrapped between two sheets of blank paper. When the electrode touched the tin-foil in the transmitter the circuit was closed; when it touched the shellac the circuit was open.The signal controlled a moving stylus in the receiver, making it touch or move back from the paper. At the end of each rotation a synchronising signal was sent, and the styluses in both machines moved 1/56" to the left before scanning the next line.The first picture sent was "an accurate picture of the first gun fired at Manila." The machine took 20-30 minutes to send the picture

Electro-chemical copying of Caselli

In 1865 Italian physics professor Giovanni Caselli established the first commercial fax system, which linked Paris and several other French cities, using a device called a Pantèlègraphe which was a modification of Alexander Bain's original idea. He transmited nearly 5,000 faxes in the first year.Made of cast iron and standing more than 2m high, this primitive but effective machine worked as follows. The sender wrote a message on a sheet of tin in non-conducting ink.The sheet was then fixed to a curved metal plate and scanned by a needle, three lines to the millimetre. The signals were carried by telegraph to the marked out the message in Prussian blue ink, the colour produced by a chemical reaction, as the paper was soaked in potassium ferro-cyanide. To ensure that both needles scanned at exactly the same rate, two extremely accurate clocks were used to trigger a pendulum which, in turn, was linked to gears and pulleys that controlled the needles.

Early fax machine

Facsimile: Sytemes (de facsimile) phototelegraphiques = Phototelegraphie or Systemes (de facsimile) documentaires = Document-telegraphyFacsimile (Fac*sim”i*le) n.; pl. Facsimiles [L. fac simile make like; or an abrivation of factum simile made like; facere to make + similes like. See fact, and Simile. ]A copy of anything made, either so as to be deceptive or so to give every part and detail of the original; an exact copy likeness.Facsimile telegraph, a telegraphic apparatus reproducing messages in autograph.Facsimile (Fac*sim”i*le), v. t. make a facsimile

fax transmission from PC to plain fax machine problem

some times the transmission doesn't even start and other times it stops by the end of the first page!i also tried to send a 2-pages fax from my pc(line b) to the other line(a) where the fax machine is on and happens the same(no problem to other receivers until now). i tried to put a different fax machine(panasonic) in the same place(a) and it worked.the wierd thing is that when i tried to change the telephone line of the pc(b) with a third one(x) and send again... no problem!so i liked this "x" line but...when i tried to send from pc(b) to the fax machine(telcom) which i placed on the (x) line i got the same problem!the 2 lines (a) and (x) are by the new "hol" provider and the third line (b) is thankfully still on the old provider "ote".i suppose it could propably has to do something with my new provider and router(onaccess) because i have this problem since i installed it.i would really appreciate any kind of help since the technical department of the provider comes with nothing every time i bring the matter !!! i was trying today again and it worked... so i called them to see what happened differently and before i say anything they told me that they face a general problem today with their servers... unfortunatelly their problem was solved but brought up mine again

Fax machines versus sliced bread

Before I complain any more, let me say that I'd rather have a fax machine than not have one. Without a fax machine, I'm just a dot on the map. With a fax, I'm connected to corporate America. And, however bad it gets, I'm never tempted to throw my fax machine out the window, something I thought of daily when dealing with dot-matrix printers. But the fax machine is not as efficient as everyone seems to think. And a lot of people misuse the beast.
Here are some of the things that get my dander up. I send a three-page fax and then get a call saying that the last page didn't arrive. It left my place intact, slipped right through the scanner and across the phone lines--did it stop for coffee along the way? Or, I send a 10-page fax but get a call saying that pages 2, 5, and 7 are missing. Obviously, those pages went through the fax two at a time. So I have to resend the vagrant pages.
On the receiving end, the same thing happens, often with an additional annoying twist. Ostensibly, I get all the pages that were sent, but here and there I see 5 or 10 blank lines, where part of a page was erased because of a less-than-smooth ride through the fax-feed rollers.
And don't you love newspaper clippings? "Isn't that a great photo?" someone will ask me, referring to a four-by-four-inch blur that looks like a bottom sample from the Mississippi River. Fax machines have controls, such as high and low contrast and fine and superfine mode, which are designed for items such as newsprint and photos. But people don't use them.
Americans love fax machines because we are fascinated by appliances. We just push buttons and the machine does the rest. But even appliances need to be told what to do. Don't people choose warm- or cold-water settings on the washer? Set controls on a toaster? How many people use broadcasting, delayed multiple polling, voice request, turnaround polling, or delayed transmission? Probably as many as program their VCRs. But setting contrast and resolution controls on a fax is no different from adjusting a television picture.
For instance, the documentation for my Hitachi says to use high contrast and superfine resolution for newspapers; for photographs and color, turn on the gray scale. I must admit I'm no more attentive than the next guy when it comes to fine tuning. When sending a news clipping, all my effort goes into guiding it through the rollers so that it doesn't rip into shreds and set off alarms.
I also learned from my documentation that low-contrast pictures or characters in a received copy might be the fault of a dirty scanning unit. "Cleaning should be done once a month," it says. Ha! Have I ever considered cleaning the scanning unit? Have you? Or the feed rollers, which might account for paper sticking together?
Here's another beauty. I fax a note to someone, and a week later, in the course of conversation, I discover that the information I sent was never received. It arrived, but was never routed to the addressee. This problem doesn't occur in home offices, where people can check their fax machines while brushing their teeth, but it is rampant in corporate offices. Not everyone has a secretary to check the fax machine every 10 minutes; and when people do walk by the machine, they pick up and route material of interest only to them or their department.
Try this on for size. I receive a faxed document with handwritten comments on it. The document itself is crystal clear, but the comments look like the last request of a madman. The commentator hasn't read his or her manual, wherein it says to use superfine resolution when sending handwriting. It should also encourage the use of a pen, not a pencil.
One of my least favorite tasks is resending a fax I've received. I get 10 pages of thermal paper, mark them up with my comments (applying ink and observing all rules of good penmanship), and prepare to resend. But if the chances of sending a stack of fresh, clean paper without suffering a jam are slim, the chances of successfully sending a stack of thermal paper are nil. In fact, you're lucky if you can get through the process without ruining one of the pages in a devastating jam that will crinkle it beyond recognition.

Portable Fax Machines

As long as fax remains an essential part of doing business, every office will have a fax machine. But what if an essential part of your business is not being in the office? How are you supposed to send and receive faxes from the road? E-mail and Internet fax technology have been a boon for road warriors, but some people still like to have that piece of paper in their hand. That's where portable fax machines come in.

Fax Machine Troubleshooting

Fax machines are complicated pieces of equipment with delicate sensors, motors and finely calibrated moving parts. As much as you might want to kick your office fax machine when there's a paper jam, there are other solutions. Here are some troubleshooting tips for the most common fax problems: image quality, paper jams and connectivity issues.
The most common image quality problems with faxes are pages that come out too dark, too light or are unreadable due to streaks, splotches and spots. For dark and light pages, it could be as simple as changing the darkness or density setting on the receiving machine [source: FineStar Imaging]. If the receiver does a test print and the page comes out clean, then the problem is most likely with the sender's machine.
The sender should open up the document feed area of the fax machine and clean all the surfaces and moving parts with a slightly damp cloth [source: Sands Office Equipment, Inc.] If the fax machine is one of those all-in-one gadgets that doubles as a scanner and copier, clean off the scanner glass as well with a little glass cleaner

How to Use a Fax Machine

Even though traditional fax machines are fast being replaced by e-mail and Internet fax services, it's still important to know how to use this workplace workhorse. Here are some basic instructions for sending and receiving a fax.
Sending a fax:
Make sure the fax machine is plugged into a power source and also plugged into a working phone jack.
Turn the fax machine on.
Obtain the fax number of the destination fax machine.
Gather the documents you want to send and put them in the order you want them to be received.
Fill out a separate piece of paper called a coversheet with the following information:
recipient's name
recipient's fax number/phone number
your name
your phone number
a short message intended for the recipient similar to the subject line of an e-mail
number of pages (including coversheet)
Lay the documents face-up in the fax machine feeder tray with the coversheet on top
Dial the recipient's fax number (dialing instructions for international calls)
Press the "fax" or "send" button, depending on the particular fax machine model

Receiving a Fax

The bits for the scanned document travel through the phone line and arrive at a receiving fax machine. The bits are decoded, uncompressed and reassembled into the scanned lines of the original document. There are five common ways to print the fax, depending on the type of machine that receives it:
Thermal paper -- When fax machines started infiltrating offices en mass in the 1980s, most of them used thermal paper. The paper is coated with chemicals that react to heat by turning black. Thermal paper has several big advantages:
It's very inexpensive to build a thermal printer.
Thermal printers have no moving parts except for the paper-feed mechanism.
There are no expendables like ink or ribbons because the paper contains the ink.
Thermal printers are nearly indestructible.
The only disadvantage is that the paper discolors over time, and it turns completely black if you leave it in a hot car.

Modern Fax Machines

A modern fax machine does not have the rotating drums and is a lot faster, but it uses the same basic mechanics to get the job done:
At the sending end, there is some sort of sensor to read the paper. Usually, a modern fax machine also has a paper-feed mechanism so that it is easy to send multi-page faxes.
There is some standard way to encode the white and black spots that the fax machine sees on the paper so that they can travel through a phone line.
At the receiving end, there is a mechanism that marks the paper with black dots.

Basic Idea Behind Fax Machines

Fax machines have been around in one form or another for more than a century -- Alexander Bain patented the first fax design in 1843 (see Science Line: Alexander Bain & the Fax Machine to learn more). If you look back at some of the early designs, you can get a very good idea of how they work today.
Most of the early designs involved a rotating drum. To send a fax, you would attach the piece of paper to the drum, with the print facing outward. The rest of the machine worked something like this:
There was a small photo sensor with a lens and a light.
The photo sensor was attached to an arm and faced the sheet of paper.
The arm could move downward over the sheet of paper from one end to the other as the sheet rotated on the drum. In other words, it worked something like a lathe.
© Chris Hondros/Getty ImagesFax machines are frequently used to send resumes and other important papers.
The photo sensor was able to focus in and look at a very small spot on the piece of paper -- perhaps an area of 0.01 inches squared (0.25 millimeters squared). That little patch of paper would be either black or white. The drum would rotate so that the photo sensor could examine one line of the sheet of paper and then move down a line. It did this either step-wise or in a very long spiral.
To transmit the information through a phone line, early fax machines used a very simple technique: If the spot of paper that the photo cell was looking at were white, the fax machine would send one tone; if it were black, it would send a different tone (see How Modems Work for details). For example, it might have sent an 800-Hertz tone for white and a 1,300-Hertz tone for black.
At the receiving end, there would be a similar rotating-drum mechanism, and some sort of pen to mark on the paper. When the receiving fax machine heard a 1,300-Hertz tone it would apply the pen to the paper, and when it heard an 800-Hertz tone it would take the pen off the paper

fax machine

Short for facsimile machine, a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image -- dividing it into a grid of dots. Each dot is either on or off, depending on whether it is black or white. Electronically, each dot is represented by a bit that has a value of either 0 (off) or 1 (on). In this way, the fax machine translates a picture into a series of zeros and ones (called a bit map) that can be transmitted like normal computer data. On the receiving side, a fax machine reads the incoming data, translates the zeros and ones back into dots, and reprints the picture.
The idea of fax machines has been around since 1842, when Alexander Bain invented a machine capable of receiving signals from a telegraph wire and translating them into images on paper. In 1850, a London inventor named F. C. Blakewell received a patent for a similar machine, which he called a copying telegraph.
But while the idea of fax machines has existed since the 1800s, fax machines did not become popular until the mid 1980s. The spark igniting the fax revolution was the adoption in 1983 of a standard protocol for sending faxes at rates of 9,600 bps. The standard was created by the CCITT standards organization and is known as the Group 3 standard. Now, faxes are commonplace in offices of all sizes. They provide an inexpensive, fast, and reliable method for transmitting correspondence, contracts, résumés, handwritten notes, and illustrations.
A fax machine consists of an optical scanner for digitizing images on paper, a printer for printing incoming fax messages, and a telephone for making the connection. The optical scanner generally does not offer the same quality of resolution as stand-alone scanners. Some printers on fax machines are thermal, which means they require a special kind of paper.
All fax machines conform to the CCITT Group 3 protocol. (There is a new protocol called Group 4, but it requires ISDN lines.) The Group 3 protocol supports two classes of resolution: 203 by 98 dpi and 203 by 196 dpi. The protocol also specifies a data-compression technique and a maximum transmission speed of 9,600 bps.
Some of the features that differentiate one fax machine from another include the following:
speed: fax machines transmit data at different rates, from 4,800 bps to 28,800 bps. A 9,600-bps fax machine typically requires 10 to 20 seconds to transmit one page.
printer type: Most fax machines use a thermal printer that requires special paper that tends to turn yellow or brown after a period. More expensive fax machines have printers that can print on regular bond paper.
paper size: The thermal paper used in most fax machines comes in two basic sizes: 8.5-inches wide and 10.1-inches wide. Some machines accept only the narrow-sized paper.
paper cutter: Most fax machines include a paper cutter because the thermal paper that most fax machines use comes in rolls. The least expensive models and portable faxes, however, may not include a paper cutter.
paper feed : Most fax machines have paper feeds so that you can send multiple-page documents without manually feeding each page into the machine.
autodialing: fax machines come with a variety of dialing features. Some enable you to program the fax to send a document at a future time so that you can take advantage of the lowest telephone rates.
As an alternative to stand-alone fax machines, you can also put together a fax system by purchasing separately a fax modem and an optical scanner. You may not even need the optical scanner if the documents you want to send are already in electronic form.


Facsimile Transmission, or fax, communications system for the electrical transmission of printed material, photographs, or drawings. Facsimile transmission is accomplished by radio, telephone, or undersea cable. The essential parts of a fax system are a transmitting device that translates the graphic material into electrical impulses according to a set pattern, and a synchronized receiving device that retranslates these impulses and prints a facsimile copy. In a typical system the fax scanner consists of a rotating cylinder, a source projecting a narrow beam of light, and a photoelectric cell. The copy to be transmitted is wrapped around the cylinder and is scanned by the light beam, which moves along the cylinder as it revolves.The output of the photoelectric cell is amplified and transmitted to the receiving end, where a similar cylinder, covered with specially impregnated paper, revolves in synchronism with the transmitting cylinder. A light of varying intensity moves along the rotation cylinder and darkens the paper by chemically reproducing the pattern of the original.

The Fax Machine

SciTech, Carbons to Computers series from the Smithsonian Institution.The facsimile machine was invented in 1842 by Alexander Bain, a Scottish clockmaker, who used clock mechanisms to transfer an image from one sheet of electrically conductive paper to another. Bain patented the "automatic electrochemical recording telegraph" in 1843.

history of fax machine

The use of the fax machine to transmit images via telephone lines did not become common in American businesses until the late 1980s, but the technology dates back to the nineteenth century. In 1843 in England, Alexander Bain (1818-1903) devised an apparatus comprised of two pens connected to two pendulums, which in turn were joined to a wire, that was able to reproduce writing on an electrically conductive surface.
In 1862, the Italian physicist Giovanni Caselli built a machine he called a pantelegraph (implying a hybrid of pantograph and telegraph), which was based on Bain’s invention but also included a synchronizing apparatus. His pantelegraph was used by the French Post & Telegraph agency between Paris and Marseilles from 1856 to 1870.
Elisha Gray (1835-1901), American inventor, born in Barnesville, Ohio invented and patented many electrical devices, including a facsimile transmission system. He also organized a company that later became the Western Electric Company.
In 1902, Arthur Korn (1870-1945) in Germany invented telephotography, a means for manually breaking down and transmitting still photographs by means of electrical wires. In 1907, Korn sent the first inter-city fax when he transmitted a photograph from Munich to Berlin.
In 1925, Edouard Belin (1876-1963) in France constructed the Belinograph. His invention involved placing an image on a cylinder and scanning it with a powerful light beam that had a photoelectric cell which could convert light, or the absence of light, into transmittable electrical impulses. The Belinograph process used the basic principle upon which all subsequent facsimile transmission machines would be based. In 1934, the Associated Press introduced the first system for routinely transmitting "wire photos," and 30 years later, in 1964, the Xerox Corporation introduced Long Distance Xerography (LDX).
For many years, facsimile machines remained cumbersome, expensive and difficult to operate, but in 1966 Xerox introduced the Magnafax Telecopier, a smaller, 46-pound facsimile machine that was easier to use and could be connected to any telephone line. Using this machine, a letter-sized document took about six minutes to transmit. The process was slow, but it represented a major technological step. In the late 1970s, Japanese companies entered the market, and soon a new generation of faster, smaller and more efficient fax machines became available.