Intens  

The "Intens" control sets the brightness of the display. In a real oscilloscope this control sets the intensity of the electron beam (this is the reason for it being called "intens" and not "brightness").

If the same image is drawn on a real oscilloscope, the phosphor on the screen gets used-up at the locations where the beam is displayed, compared to other locations. Therefore the intensity of the beam should be turned down when the CRO is not used. When measuring, the intensity should only be turned up just enough to get a visible waveform, in order to preserve the phosphor screen.