Donald James Leslie was born on April 13, 1911. He created and manufactured the Leslie speaker that refined the sound of the Hammond organ and helped popularize electronic music. He died on September 2, 2004.


The invention of the phototransistor was announced on March 30,1950 ( Murray Hill NJ). This was a transistor operated by light rather than electric current, invented by Dr. John Northrup Shive of the Bell Telephone Laboratories at Murray Hill, N.J. It used a tiny chip of germanium, a semiconductor material, but only a single collector wire. The tip of this wire rests in a small dimple ground into one side of the germanium disk. At this point the germanium disk is only three thousandths of an inch thick. Light focussed on the opposite, un-dimpled side of the disk can control the flow of current in the wire, thus making a control device similar in function to a photo-electric cell.

