Fax (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. 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 instantenous, yet its disadvantages in quality and its proprietary format have relegated it to a position beneath email as the prevailing form of electronic document transferral.
There are several different indicators of fax capabilities: Group, class, data transmission rate, and conformance with ITU-T (formerly CCITT) recommendations.
For those who do not own a fax machine themselves, a fax machine can be contacted by another fax machine with a series of unique numbers (like a telephone number). Fax machines cannot be contacted by home lines or mobiles.
Prior to the introduction of the now ubiquitous fax machine, one of the first being the Exxon 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 to be converted to an electrical signal varying in frequency. This audio tone was then transmitted 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.
In 1985, Dr. Hank Magnuski, founder of GammaLink, produced the first computer fax board, called GammaFax.
