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En telefaks (ofte forkortet faks; eg. telefaksimile) er en telekommunikasjonsteknologi for overføring av trykket informasjon, som dokumenter, brev, tegninger og fotografier, spesielt ved bruk av rimelige apparater over et telefonnett.
En telefaksmaskin er i all vesentlighet en kombinasjon av en scanner, et modem og en printer. Scanneren konverterer trykket informasjon til digitale bilder, modemet sender bildeinformasjonen over en telefonlinje og printeren i den andre enden skriver ut en kopi av det opprinnelige dokumentet.
Although fax machines of some sort or another have existed since the mid-late 19th century (see "History" below), modern fax technology became feasible only in the mid-1970s as the sophistication and cost of the three underlying technologies dropped to a reasonable level. Fax machines first became popular in Japan, where they had a clear advantage over competing technologies like the teleprinter; at the time, before the development of easy-to-use input method editors, it was faster to handwrite kanji than to type the characters. Over time, faxing gradually became affordable, and by the mid-1980s, fax machines were very popular around the world.
Although most businesses still maintain some kind of fax capability, the technology appears increasingly dated in the world of the Internet.
Fax communications cannot be hacked, is a legally binding document, and continues to be a critical communications tool for hospitals, insurance and financial companies, radiology groups, and manufacturing organizations. Companies use fax server technology products to automatically route inbound and outbound faxes to and from users, groups and departments, electronically, taking advantage of corporate standard analog, digital or VoIP telecommunications infrastructure.
So while "fax machines" themselves are becoming more and more obsolete, the technology and fax transmission is still key for many businesses - small, medium and enterprise.
Et populært alternativ er å abonnere på en internettbaser fakstjeneste. Fakstjenester som er levert via internett lar brukere sende og motta telefaks fra deres egen pc ved bruk av deres egen epostadresse. Med slike tjenester trenger man ikke faksserver, teleline eller en telefaksmaskin. Telefakser blir mottat hos brukeren på enten .Tiff eller .PDF format levert som et epostvedlegg. Dermed kan man sende og motta telefakser fra hele verden så lenge man har tilgang til internett. I norge leverer blandt annet Telenor og Telsys dette i all hovedsak til bedrifter.
En annen mulighet er å bruke en datamaskin og sette den opp som en telefaksserver som bruker telenettet.
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 World's Fair 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 Xerox Qyx 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 tranmitted 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.
I 1985, Dr. Hank Magnuski, stifter av GammaLink, produced the first computer fax board, called GammaFax.
Kategori:Telekommunikasjon