In fact one of the earliest examples of an image being captured, transmitted, and reproduced by electromechanical means occurred in 1842, only five years after Queen Victoria had ascended to the throne, when a Scotsman – Alexander Bain – came up with a rather ingenious idea.

Bain created an image to be transmitted by snipping it out of a thin sheet of tin, placing this representation on a moveable base, and connecting it to one side of a battery. He then created a pendulum using a conducting metal wire and a weight ending in a sharp point, and he set this device swinging above the base. The base was slowly moved under the pendulum, where the swinging weight made periodic contact with the metal image, thereby completing the electrical circuit and converting the dark and light areas of the image (represented by the presence and absence of tin) into an electrical signal.

Bain then used this signal to control a relay, which was moving back and forth in time with the pendulum. When activated, the relay pushed a pencil down onto a piece of paper mounted on a second base moving at the same rate as the first, thereby reproducing the image as a pencil drawing.

Obviously, Bain's device had little application with regard to the transmission of moving pictures, but it certainly wasn't a wasted effort, because he had essentially created the precursor to the modern Fax machine.

Displaying moving pictures on a toaster
When it comes to displaying moving pictures, we should certainly not forget the work of Denis Redmond who, in 1878, used an array of photocells to capture images and an array of glowing platinum wires to display them. Had Redmond increase the size of his platinum-wire array, it would have had the added advantage of being able to double-up as a toaster!

If you're interested, you can find out more information on these and related topics in my paper on The Origin and Evolution of Computer Displays.

Questions? Comments? Feel free to email me – Clive "Max" Maxfield – at max@techbites.com). And, of course, if you haven't already done so, don't forget to Sign Up for our weekly Programmable Logic DesignLine Newsletter.