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SC4020: Charactron Tube
SC4020 and the Charactron Tube
The speed of the SC4020 came from the charactron tube. The tube was developed by Convair in 1948 and appeared for the first time in a microfilm recorder in 1954. Large charactron tubes were used as the main interactive display terminals in the US SAGE system air defense system.
The charactron tube places a mask in the tube shaped like the characters of the alphabet. The beam, on its way to the tube face, gets extruded though the mask and takes on the appearance of the character. In consequence, characters can be displayed at high speed on the tube face. The following excerpt from a Stromberg-Carlson promotion film for the SC4020 describes the charactron tube's basic principles.