Hummel's Telediagraph, 1898
by Marcus L. Rowland
The Telediagraph was one of several early fax-like devices sending pictures via telegraph lines. It was invented circa 1895 by Ernest A. Hummel, a watchmaker of St. Paul, Minnesota.
The first machines were installed in the office of the New York Herald in 1898. By 1899, Hummel had improved the machine and the newspaper had machines in the offices of the Chicago Times Herald, the St. Louis Republic, the Boston Herald, and the Philadelphia Inquirer.
The system used synchronised rotating 8-inch drums, with a platinum stylus used as an electrode in the transmitter. The original image was drawn on 8x6" tin-foil using a non-conducting ink made from shellac mixed with alcohol. The image was received on carbon paper wrapped between two sheets of blank paper. When the electrode touched the tin-foil in the transmitter the circuit was closed; when it touched the shellac the circuit was open.
The signal controlled a moving stylus in the receiver, making it touch or move back from the paper. At the end of each rotation a synchronising signal was sent, and the styluses in both machines moved 1/56" to the left before scanning the next line.
The first picture sent was "an accurate picture of the first gun fired at Manila." The machine took 20-30 minutes to send the picture.
Near-copies of this and similar mechanisms were in use until the 1970s, although transmission speeds were improved and photocells allowed plain paper originals and photographs to be transmitted. The basic principle was also applied to stencil-cutting machines for ink duplicators.
The original Telediagraph article is available from me on disk with illustrations (see my web page for details), and is now downloadable from a file server; send a message to email@example.com with the title "help" and no contents for the details.
Marcus L. Rowland (firstname.lastname@example.org)