An oscilloscope is an electronic instrument widely used in making electrical measurements, such as measuring clock rates, clock pulse widths, and voltage levels. An oscilloscope's main component is a CRT, which is a vacuum tube in which electrons are accelerated and deflected under the influence of an electric field. The tube's neck contains two sets of plates placed at right angles to each other which deflect the electrons in various directions. The result is a graphical display of the measured signal on the CRT's face.