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 Most people might think that the fax machine,
found in many offices and homes, is a relatively new piece of
technology. In fact, a patent for the fax machine was issued in
1843, 33 years before the telephone! A Scottish clockmaker,
Alexander Bain, invented this device in the same year that the first
telegraph message was being sent across America.
Although Bain worked out the method, he never actually sent a fax
transmission. It was not until 1865 that the first working fax
machines and transmission service were set up. An Italian Abbot named Giovanni Caselli developed the
"pantelegraph" which was used to send
pictures and writing between French cities.
The way that a fax machine works is quite straightforward. A
sensor scans horizontally across the
sheet one line at a time - like your eyes when you're reading a
book. If the sensor sees a white patch it records a 0, and if it
sees a dark patch it records a 1. In this way the whole page is
"digitised" into a string of 0s and 1s. A modem turns this into a series of high or low
pitched sounds that are sent down the phone line to a remote receiver. At the other end, the sounds are
turned back into 0s and 1s. These are printed onto a piece of paper
as light or dark dots, and so the original picture is reproduced
hundreds of miles away.
For the very first fax machines, the pictures had to be printed
onto tin foil with non-conducting ink.
An electrode scanned across the surface
and sensed a light or dark patch depending on the current that
flowed. The transmitting and receiving machines had drums that spun
at the same speed, and every revolution clicked 0.5mm to the left so
that eventually the whole picture was scanned. These machines took
about half an hour to send a 20cm x 15cm photograph.
But faxes didn't really take off until the 20th century. In 1902
Dr Arthur Korn developed a fax machine with an optical scanner that allowed plain paper
images to be sent. This is basically the same design used today,
with the received image being printed on heat-sensitive paper. Nowadays a
photojournalist can send a high-resolution
picture to his newspaper headquarters in less than a minute.
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