Smart Machines

True or false: the fax machine is a relatively recent invention that depends on telephone lines for its transmissions. Answer: False.

Alexander Graham Bell filed his famous patent on the telephone on February 14, 1876, more than 122 years ago. But the first patent on a working fax machine had already been filed and granted before Bell was even born. It went to the Scottish clock maker and inventor Alexander Bain in 1843.

Bain's method for sending a facsimile image cleverly exploited the transmission of electrical signals over telegraph wires. The telegraph was a relatively new device in Bain's day but was rapidly gaining in popularity. Both amateur and professional inventors were trying their utmost to find new ways to use it, just as today both amateur and professional technophiles are striving to come up with new ways to use the Internet.

The principle behind Bain's faxing process was quite simple. The sending machine used a detector to scan an image or text line by line, point by point. As the detector swept over the page left to right, it emitted an electrical signal, which registered at one strength as it passed through the image's black points (ink) and at another as it passed through the image's white points (absence of ink). The two distinct signals traveled over a telegraph wire to the receiver, which applied them to chemically treated paper. As the signals passed through the paper they left behind the black and white dots that had defined the original image. Remember the smelly fax paper from the 1970s? It was all Bain's fault.

Bain's biggest problem was figuring out how to synchronize the detector and the receiver so they would begin and end the scan lines at the same point. He solved it by constructing the sending and the receiving machines as large metronomes--using one pendulum to control the swing of the scanning detector at the sender and another pendulum to hold the recording device at the receiver. The pendulums had to be synchronized once, at the start of a session, but would then reliably stay in sync without requiring further adjustments.

The Italian Giovanni Caselli built a huge version of Bain's fax machine in 1856, which he called a pantelegraph ("all-purpose telegraph"). Caselli's machine was used in November 1860 to send the first long-distance facsimile between two cities--a message that traveled the 70 miles from Paris to Amiens. The device employed synchronized pendulums stretching about eight feet high--not quite a desktop device yet.

By the 1920s facsimile transmission had become sufficiently precise to allow photographs to be transmitted between New York and London for use in newspapers, though the process still took several hours per photo. Desktop fax machines as we know them did not become popular until the late 1970s. Indeed, it took a long time for the fax machine to become an overnight success.

Gerard J. Holzmann is a member of the technical staff in Computing Sciences Research at Bell Laboratories, in Murray Hill, N.J.