The Braun tube

The Braun tube, this small early 1900 tube is in fact a cold Cathode Crookes tube with an internal mica screen covered with phosphorescent paint. The neck contains a glass diaphragm with a small 2mm hole to let only a tiny electron beam go through  (focus) which can be deflected by an (electro) magnet to produce a spot on the screen.  Click here to see the family of educational CRT's sold by Max Kohl early 1900 and here by Müller-Uri.

Karl Ferdinand Braun a German physicist, interested in the just discovered Cathode rays worked and experimented with Crookes tubes. When he was working at the Physics Institute of the Strasbourg University (from 1895-1918) he developed the first cold Cathode Ray tube with magnetically beam deflection (the effect discovered by Plucker and Hittorf in 1869) and a mica screen covered with phosphor to produce a visible spot. The tube, build for him by Franz Müller successor of Geissler was called after its inventor, the Braun tube. Braun used this tube as an indicator tube for studying the effects of Cathode rays in order to visualize alternating currents and described this 1897, this was in fact the first oscilloscope. Harris J Ryan introduced this tube in 1903 in the USA as an alternating current wave indicator, known as the Braun-Ryan tube.
The first ideas of using Cathode rays (Braun's tube) for Television came from the Englishman Campbell Swinton in 1908. The Frenchman Rignoux and the Russian Rosing experimented also with the Braun's tube for the same reason, just like Belin and Holweck who used Cathode rays for their TV receiver and demonstrated it in Malmaison in 1928. At that time, mechanical TV was the only way to transmit moving images, mostly with a Baird, TeKaDe, or Jenkins (US) mechanical receiver.

                                                                   Karl Ferdinand Braun

                                                                          1850-1918