DVBST

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DVBST was an acronym used by Tektronix to describe their line of "Direct-View Bistable Storage Tubes". These were cathode ray tubes (CRTs) that stored information written to them using an analog technique inherent in the CRT and based upon the secondary emission of electrons from the phosphor screen itself. (See the discussion of "Analogue Storage" in the oscilloscope article.) The resulting image was visible in the continuously glowing patterns on the face of the CRT.

DVBST technology was anticipated by Andrew Haeff of the (United States) Naval Research Laboratory, and by Williams and Kilburn in the late 1940s. Tek's Bob Anderson reduced to practice the science and technology in the late 1950s to yield a reliable and simple DVST.

DVBSTs were used for analog oscilloscopes (first in the 564 oscilloscope, then the 601 monitor, the 611 monitor, the 7613 plug-in mainframe oscilloscope, all from Tektronix) and for computer terminals such as the archetypal Tek 4010 (the "mean green flashin' machine") and its several successors including the Tektronix 4014. Portions of the screen are individually written-to by a conventional electron beam gun, and "flooded" by a wide, low velocity electron gun. Erasure required erasing the entire screen in a bright flash of green light, leading to the nickname.

Some DVBST implementations also allowed the "write-through" of a small amount of dynamically refreshed, non-stored data. This allowed the display of cursors, graphic elements under construction, and the like on computer terminals.

Another version of a DVBST was the "dark trace" CRT which was produced by Thomas Electronics and others in the early 1970s. This CRT replaced the phosphor screen with a translucent membrane coated with Potassium Chloride (KCl). KCl had the property that when struck by an electron that spot would turn opaque. By back lighting such a CRT with a white or green circuline fluorescent lamp, the resulting image would appear as black information against a green background or as magenta information against a white background. The image would be retained until erased by flooding the membrane with a high-intensity flash of light or by thermal heating. Using conventional deflection and raster formation circuity a bi-level image could be created on the membrane and retained even when power was removed from the CRT. By using an array, say 8 X 8, of dots, a larger pixel could be formed to represent 64 gray levels. One such device, the D38 Image Display, was made by DICOMED Corporation and a technical paper was presented at the 1972 Electro-Optical Conference in Geneva, Switzerland.