That's when a British scientist named John A. Fleming made a vacuum tube known today as a diode. Then the diode was known as a "valve," because it forced current in the tube to travel exclusively in one direction.
Getting that single directional flow was critical for radio sets which needed to turn alternating current into direct current. The vacuum tube didn't reach its full maturity until Lee De Forest came along a decade later.
De Forest invented something he called the "audion. De Forest put a metal grid in the middle of the vacuum tube. Otto von Guericke first produces an air pump that is able to create a partial vacuum.
A vacuum was required for the operation of thermionic valves. Julius Plucker demonstrates that magnetic fields can bend rays of what are later called cathode rays. Sir William Preece replicates the Edison effect and makes measurements, presenting a paper to the Royal Society. Guglielmo Marconi sets up his Wireless telegraph and Signal Company to exploit radio or 'wireless' technology. Marconi makes the first transatlantic radio transmission, but difficulties were encountered with detecting he signals.
Ambrose Fleming rectifies wireless signals using what he terms his oscillation valve - this is the first time the Edison effect has been used. It was a simple diode valve and sometimes referred to as a Fleming Diode. Having undertaken many experiments, Lee de Forest in the USA adds a third electrode to Fleming's diode to produce what he termed his Audion. This device was still only used for rectification.
Ambrose Fleming replaces the carbon filament normally used in the diode valve with a tungsten filament. In France the first hard vacuum triode was made.
This was to become a major manufacturer of valves and then transistors. The tube was standard equipment in radio receivers, radar sets, early television sets and other forms of electronic communication for at least half a century, until it was replaced by solid-state electronics in the midth century. The principle of thermionic emission , essentially the transmission of a charged current using a heated conductor, was certainly well-understood before Fleming incorporated it into his tube.
Langmuir devised a more efficient vacuum pump in ; with a better vacuum, the tubes lasted longer and were more stable. Indirect heating improved tube efficiency. Triodes were limited to low frequencies of less than one megahertz. In American physicist Albert Wallace Hull invented the tetrode to eliminate high-frequency oscillations and improve the frequency range.
A year later the pentode, which improved performance at low voltage, was developed and became the most commonly used valve. Over the course of years, a variety of vacuum tubes came into use.
Photo tubes were used in sound equipment, making it possible to record and retrieve audio from motion picture film. The cathode-ray tube focused an electron beam, leading to the invention of oscilloscopes, televisions, and cameras. Microwave tubes were used in radar , early space communication, and microwave ovens. Storage tubes, which could store and retrieve data, were essential in the advancement of computers.
Despite its numerous advantages, the vacuum tube had many drawbacks. It was extremely fragile, had a limited life, was fairly large, and required a lot of power to operate its heating element.
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