Telefunken was a German radio and television producer, founded in Berlin in 1903 as a joint venture between Siemens & Halske and the Allgemeine Elektrizitäts-Gesellschaft (AEG) . Prior to World War I the company set up the first world wide network of communications and was the first in the world to sell electronic televisions with cathode ray tubes, in Germany in 1934.

A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a frame of video on an analog television set (TV), digital raster graphics on a computer monitor, or other phenomena like radar targets. A CRT in a TV is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons.