I did not know that yesterday!

Fax (short for facsimile - from Latin "fac simile", "make similar",
i.e. "make a copy" - or telefacsimile) is a telecommunications technology used to transfer copies of documents, especially using affordable devices operating over the telephone network. The words telecopy and telefax are also used as synonyms.

Overview
A fax machine is essentially an image scanner, a modem, and a computer printer combined into a highly specialized package. The scanner converts the content of a physical document into a digital image, the modem sends the image data over a phone line, and the printer at the other end makes a duplicate of the original document.

Obviously, a very high-quality fax machine with some additional electronics can connect to a computer, and can be used to scan documents into a computer, to print documents from the computer, and to make photocopies. Such high-end devices are called multifunction printers and cost more than fax machines.

Modern fax technology became feasible only in the mid-1970s as the sophistication and cost of the three underlying technologies improved to a reasonable level. Fax machines first became popular in Japan, where they had an clear advantage over competing technologies like telex; it is faster to write Japanese ideographs than to type them. Over time, they gradually became affordable and were very popular around the world by the mid-1980s.

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

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


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.

In 1861 the first fax machine, Pantelegraph, was sold by Giovanni Casselli - before even 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 in November 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.

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