30th August 1940. Valves and Tubes.

Until 1897 atoms were thought to be the ultimate particle, until J.J. Thomson who died Today in 1940, by using a Cathode Ray Tube (CRT), showed that the stream of rays created were unknown negatively-charged particles, he called corpuscles, later described as electrons.(1)

These Cathode Rays were observed using Sir William Crooke’s ‘Vacuum Tube’ who had been instrumental in developing the first practical CRT between 1869-75.

Cathode Ray Screen

Cathode Ray Screen: 1. three electron emitters. red,green,blue, phosphorous dots. 2. electron beam. 6. anode. 7 phosphorous layer. 8. close up of inner screen.

This CRT had 2 electrodes: the negatively charged Cathode and the positively charged Anode.(2)

The Cathode is a heated filament inside a vacuum in a glass tube, like a light bulb, which releases a stream of negative Electrons into the vacuum and attracted to the positive Anode.

In a TV using CRT this stream is focused and accelerated onto the phosphorous-coated screen causing it to glow.

However all the above was dependent on the glass company Chance Bros.which had developed Cathode Ray Tubes before World War II using Borosilicate Glass (silica and boron oxide) similar to Pyrex.(3)

Early radios relied on electrodes, but via Vacuum Tubes, commonly called Valves acting as switches and used in early computers  when in WWII telephone engineer Tommy Flowers used them in the analogue computer Colossus, at Bletchley Park.(4)

Radio Valve

Radio valves used in pre-transistor sets.

These valves (Fleming Tubes), replacing the ‘cat’s whisker’ in radios, were eventually to be the mainstay of a wide range of technology including telephone networks, radar, sound reproduction, analogue and digital computers and TV, but now replaced by solid-state devices: transistors, microchips.

(1) Thomson was born on 18th December 1856 a science now employed in electronic-guns and electron-microscopes.

(2) Electrode (from electron and ‘hodes’-away), is a conductor which contacts a non-metal part of a circuit such as semi-conductor, electrolyte, vacuum or air.

(3) Based on William Crookes (17.6.1832-4.4.1919) technology the Chance Brothers were responsible for glass for the earliest optical lenses to block UV whilst keeping transparency and The Crookes Trade Mark was retained by Chance until the 1960.s.

(4) Invented by John Ambrose Fleming.





shinyshack.com/Pic of valve.



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About colindunkerley

My name is Colin Dunkerley who having spent two years in the Royal Army Pay Corps ploughed many a barren industrial furrow until drawn to the 'chalk-face' as a teacher, now retired. I have spent the last 15 years researching all aspects of life in Britain since Roman times.

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