Williams Tube, c 1950.

The Williams Tube is a memory device for storing digital information in computers. The device is named after FC Williams (1911-1977) who developed it in Manchester towards the end of World War II. The first tubes used were cathode ray tubes of the kind used in radar displays. A working version was demonstrated in 1948. Information is stored as an electrostatic charge held by the phosphor coating on the screen which glows when struck by electrons. The pattern of charges is continuously refreshed and represents the digital information being stored.