Clock-maker Alexander Bain used the pendulum's swing to create early fax machines.

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The Science Behind Fax Machines

The process Bain used relied on electrochemistry and mechanics, which he mastered during his days as an instrument and clock maker. Bain saw that telegraphs of the day were slowed by simple mechanics. He also noted that invention relied on electrical impulse, which he thought could be harnessed in a way that would create visual messages, speeding the process.

The chemical telegraph Bain invented, which would later be modified to become the first fax machine, at first simply sent "long" and "short" lines, which a telegraph operator could interpret quickly. The process was a success and the electrochemical process it used was a major leap forward for future fax technology.

Bain later applied the chemical telegraph idea to sending images. To send rudimentary pictures, Bain made a copy of the picture in copper and then discarded everything except the actual lines of the picture he wanted to send.

His process next used a pair of pendulums, synchronized at a distance by an electromagnet. He fitted the pendulum with a contact beneath it and swung it over the copper picture. Each time the contact touched the copper image, it would send an electrical impulse racing over the wire to the identical synchronized pendulum swinging over some chemically treated paper. The chemical in the paper darkened when touched by the energized pendulum. Both the sending picture and the receiving paper moved beneath each pendulum by 1 millimeter following each pendulum swing, resulting in a "scan" of the original and a copy printed on the other end, which eventually resulted in the copper image from the sending pendulum being duplicated on the paper.

Bain used a solution of nitrate ammonia and purssiate of potash to treat the paper that received the picture. When touched by the electrical impulse, the solution decomposed leaving a bluish stain. This created the first fax pages.

How does today's modern fax machine work? Go to the next page to find out.