The time it takes for the phosphor to become fully activated is actually longer than the pulse representing the timing to draw a single pixel (40 nanoseconds). Meaning, if we were to attempt to display just a single pixel, the phosphor on this particular spot will never reach its full activation level resulting in a fuzzy image of varying brightnesses between dimmer, thin strokes and heavier, thick strokes. So the typography has to adjust for this, by streching the pulses to double width (80 ns), at least, in order to provide an even image and legible text and to work around the shallow flanks of the screen intensification. [...]

To provide for this, the VT-terminals employ a special technique, called dot stretching: The individual rows of a character matrix as in ROM are modified on-the-fly by prolonging any pulses for an active pixel for yet another pixel. Where there's a single pixel in ROM, there will be two on the screen, where there are two in a row, there will be three displayed. (This is equivalent to OR-ing a word with itself by an offset of one pixel or bit to the right.)

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