CATHODE RAY OSCILLAGRAPH, 1930's
A Later version having an Octal base, of the Brimar 'Cathode-Ray Oscillagraph', similar to the 'Tunograph' but used to monitor modulating current for experimental purposes.
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The spot of light produced on the screen at the top could move across the screen in three dimensions. Unlike the 'Tunograph'. The earliest version of the CRT was invented by the German physicist Ferdinand Braun in 1897 and is also known as the Braun tube.
It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen.