Thinking about Fax Technology

Overview:

We generally think of the fax machine as a descendant of the telephone, but its fundamental processes were discovered well before the telephone was even invented. On May 27, 1843, the Scottish inventor Alexander Bain filed a patent for the first contraption designed to convert images into electrical impulses and send them over wire. Dependent largely on Samuel Morse's invention of the telegraph, which made possible the transmission of written messages over wire, Bain called his machine a "recording telegraph" because of its ability to draw images rather than write messages over great distances.

In the early 20th century, Bain's invention was modified and refined by inventors around the world, but his original conception for the device remained the same. By the 1930s and 1940s, fax and "wire photo" machines were used regularly by news agencies, weather services, and the military to transmit images. The costly and cumbersome equipment and impractically long transmission times, however, limited the technology's general use for decades. It was not until the development of digital fax technology in the late 1970s and 1980s that the device became feasible for the everyday business user. Digital technology allowed for sending higher quality reproductions much faster than earlier analogue counterparts. The increasing affordability of electronics manufacturing during the period quickened the fax machine's wide adoption in the modern office. The rise of the Internet in the 1990s posed a challenge to fax technology as document scanning and email technologies replaced many of the fax machine's central functions. Nevertheless, it has remained a technological mainstay of the modern workplace.

So how does the modern fax machine work? To send a document via fax, first you need to tell the machine where you'd like to send it by dialing the receiver's fax number. After initiating the process, the machine will feed your document past a photosensitive scanning mechanism, which converts the visual information on your document into electrical signals. The fax machine will then encode these signals into a digital binary language of 1s and 0s. This process allows your fax machine to compress data and send documents faster. The 1s and 0s are then converted into an analogue signal so that it may travel over the phone lines.

The sending machine then "dials up" the receiving machine, which hears the chirping sound of the sending machine's CNG tones (or calling tones). These tones instruct the receiver to gather the transmission and convert it back into binary coding. After the receiving fax machine decompresses the transmission, it prints the document using a printing mechanism. Older fax machines print on a roll of thermal paper, which registers an image when the printing mechanism exposes it to heat. Today, most fax machines employ laser or inkjet printing technologies, which are commonly used in office or home printers.