From AMS Glossary
(Abbreviated CRT.) A vacuum tube consisting essentially of an electron gun producing a concentrated electron beam that impinges on a phosphorescent coating on the back of a viewing face or screen.
The excitation of the phosphor produces light, the intensity of which is controlled by regulating the flow of electrons. Deflection of the beam is achieved either electromagnetically by currents in coils around the tube or electrostatically by voltages on internal deflection plates.