Abbreviation for Cathode-Ray Tube, the technology used in most televisions and computer display screens. A CRT works by moving an electron beam back and forth across the inside front of the screen. Each time a beam makes a pass across the screen, it lights up phosphor dots on the inside, illuminating the active portions of the screen. The beam is controlled by electromagnetism, which causes it to scan in an orderly fashion that is related in time to the data (image) that causes the energy from the gun to vary, thereby producing (painting) the images you see. By quickly drawing (scanning) many such lines from the top to the bottom of the screen, it creates an entire screen full of images. In order for the beam to return to the top of the screen after it has reached the bottom a “blanking pulse” is timed into the data to turn the beam off so it doesn’t paint a diagonal line from the lower right to the upper left hand corner. This blanking pulse is known as black burst and is the source of timing used in many synchronization systems.