The telautograph is an ancestor of the modern fax machine. It transmits electrical signals representing the position of a pen or tracer at the sending station to repeating mechanisms attached to a pen at the receiving station, thus reproducing at the receiving station a drawing, writing, or signature made by the sender. It was the first such device to transmit drawings to a stationary sheet of paper; previous inventions in Europe had used a constantly moving strip of paper to make such transmissions and the pen could not be lifted between words. Surprisingly, at least from a modern perspective, some early telautographs used digital/pulse-based transmission while later more successful devices reverted to analog signaling.
The inventor Elisha Gray
Elisha Gray's Telautograph Transmitter and Receiver in use
Foster Ritchie's Telautograph Receiver and Transmitter c. 1904
Sample work of telautograph
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.
This fax machine from 1999 used relatively new inkjet printing technology on normal paper.
Like many fax machines, this 1990 model used thermal printing on relatively expensive thermal paper which came in rolls. The roll was inserted into a compartment in the machine.
Input (left) and output (right) of a telautograph transmission
Children read a wirelessly transmitted newspaper in 1938.