Giovanni Caselli was an Italian priest, inventor, and physicist. He studied electricity and magnetism as a child which led to his invention of the pantelegraph, the forerunner of the fax machine. The world's first practical operating facsimile machine ("fax") system put into use was by Caselli. He had worldwide patents on his system. His technology idea was further developed into today's analog television.

Fax, sometimes called telecopying or telefax, is the telephonic transmission of scanned printed material, normally to a telephone number connected to a printer or other output device. The original document is scanned with a fax machine, which processes the contents as a single fixed graphic image, converting it into a bitmap, and then transmitting it through the telephone system in the form of audio-frequency tones. The receiving fax machine interprets the tones and reconstructs the image, printing a paper copy. Early systems used direct conversions of image darkness to audio tone in a continuous or analog manner. Since the 1980s, most machines transmit an audio-encoded digital representation of the page, using data compression to more quickly transmit areas that are all-white or all-black.