Saturday, August 25, 2012

Partially Inverted Sequence

I’ve always thought that the evolution of communications over distance went something like this: smoke signals, carrier pigeon, semaphore, telegraph,  land line telephone, fax, cell phone, and then today’s digital communications (text, images, audio, video) over the Internet.  I was recently surprised to learn, however, that the sequence above is partially inverted!

The fax technology with which we are all familiar involves the transmission of scanned printed material (text and/or images) over telephone lines.  This particular technology was introduced by the Xerox Corporation in the 1960’s, obviously much later than the invention of the telephone in the 1870’s.  So we assume that the telephone came first, and then, much later, the fax.  However, that is not the case at all!  In fact, fax machines were around long before the telephone came along.  Early faxes simply used different methods of transmission.

From Wikipedia’s article on Scottish inventor Alexander Bain:

Bain worked on an experimental facsimile machine in 1843 to 1846. He used a clock to synchronise the movement of two pendulums for line-by-line scanning of a message. For transmission, Bain applied metal pins arranged on a cylinder made of insulating material. An electric probe that transmitted on-off pulses then scanned the pins. The message was reproduced at the receiving station on electrochemically sensitive paper impregnated with a chemical solution similar to that developed for his chemical telegraph. In his patent description dated 27 May 1843 for "improvements in producing and regulating electric currents and improvements in timepieces, and in electric printing, and signal telegraphs," he claimed that "a copy of any other surface composed of conducting and non-conducting materials can be taken by these means". The transmitter and receiver were connected by five wires.

Alas, Bain’s invention, although later improved by Frederick Bakewell, produced poor images and was not commercially viable.  However, then came Italian physicist Giovanni Caselli with his Pantelegraph.  From Wikipedia:

Caselli developed an electrochemical technology with a "synchronizing apparatus" (regulating clock) to make the sending and receiving mechanisms work together that was far superior to any technology Bain or Bakewell had.  The technology is relatively simple. An image is made using non-conductive ink on a piece of tin foil. A stylus, that is in the electrical circuit of the tin foil, is then passed over the foil where it lightly touches it. The stylus passes with parallel scans slightly apart. Electricity conducts where there is no ink and does not where there is ink. This causes on and off circuits matching the image as it scans. The signals are then sent along a long distance telegraph line. The receiver at the other end has an electrical stylus and scans blue dye ink on white paper reproducing the image line-by-line, a fac simile (Latin, "make similar") of the original image.

Caselli’s invention was implemented in “the first commercial telefax service between Paris and Lyon in 1865, some 11 years before the invention of telephones.”

So not only does the fax predate the telephone, but fax transmission media evolved from direct wire (Bain in 1846), to telegraph lines (Caselli, 1865) and to wireless via radio (RCA in 1924) long before Xerox introduced fax over telephone lines in 1964.  Interestingly, the radio facsimile developed by RCA in the 20’s “is still in common use today for transmitting weather charts and information to ships at sea”.

I had no idea!