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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.
Cathode rays or electron beams (e-beam) are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode. They were first observed in 1859 by German physicist Julius Plücker and Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays. In 1897, British physicist J. J. Thomson showed that cathode rays were composed of a previously unknown negatively charged particle, which was later named the electron. Cathode-ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to render an image on a screen.
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic CCD for Cathode Current Departs. A conventional current describes the direction in which positive charges move. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode.
Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, entertainment, news, and sports. The medium is capable of more than "radio broadcasting," which refers to an audio signal sent to radio receivers.
A vacuum tube, electron tube, valve, or tube is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
A cold cathode is a cathode that is not electrically heated by a filament. A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone. It is used in gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube. The other type of cathode is a hot cathode, which is heated by electric current passing through a filament. A cold cathode does not necessarily operate at a low temperature: it is often heated to its operating temperature by other methods, such as the current passing from the cathode into the gas.
Vladimir Kosma Zworykin was a Russian-American inventor, engineer, and pioneer of television technology. Zworykin invented a television transmitting and receiving system employing cathode ray tubes. He played a role in the practical development of television from the early thirties, including charge storage-type tubes, infrared image tubes and the electron microscope.
Allen Balcom DuMont, also spelled Du Mont, was an American electronics engineer, scientist and inventor who improved the cathode ray tube in 1931 for use in television receivers. Seven years later he manufactured and sold the first commercially practical television set to the public. In June 1938, his Model 180 television receiver was the first all-electronic television set sold to the public, a few months prior to RCA's first TV set in April 1939. In 1946, DuMont founded the first television network to be licensed, the DuMont Television Network, by linking station WABD in New York City to station W3XWT, which later became WTTG, in Washington, D.C. WTTG was named for Dr. Thomas T. Goldsmith, DuMont's Vice President of Research, and his best friend. DuMont's successes in television picture tubes, TV sets and components and his involvement in commercial TV broadcasting made him the first millionaire in the business.
Alan Archibald Campbell-SwintonFRS was a Scottish consulting electrical engineer, who provided the theoretical basis for the electronic television, two decades before the technology existed to implement it. He began experimenting around 1903 with the use of cathode ray tubes for the electronic transmission and reception of images. Campbell described the theoretical basis for an all electronic method of producing television in a 1908 letter to Nature. Campbell-Swinton's concept was central to the cathode ray television because of his proposed modification of the cathode ray tube that allowed its use as both a transmitter and receiver of light. The cathode-ray tube was the system of electronic television that was subsequently developed in later years, as technology caught up with Campbell-Swinton's initial ideas. Other inventors would use Campbell-Swinton's ideas as a starting-point to realise the cathode ray tube television as the standard, workable form of all electronic television that it became for decades after his death. It is generally considered that the original credit for the successful theoretical conception of using a cathode ray tube device for imaging should belong to Campbell-Swinton.
Philipp Eduard Anton von Lenard was a Hungarian-born German physicist and the winner of the Nobel Prize for Physics in 1905 for his work on cathode rays and the discovery of many of their properties. One of his most important contributions was the experimental realization of the photoelectric effect. He discovered that the energy (speed) of the electrons ejected from a cathode depends only on the frequency, and not the intensity, of the incident light.
An electron gun is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy.
An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast to other sources of ionizing radiation, X-rays are only produced as long as the X-ray tube is energized. X-ray tubes are also used in CT scanners, airport luggage scanners, X-ray crystallography, material and structure analysis, and for industrial inspection.
A Geissler tube is a precursor to modern gas discharge tubes, demonstrating the principles of electrical glow discharge, akin to contemporary neon lights, and central to the discovery of the electron. This device was developed in 1857 by Heinrich Geissler, a German physicist and glassblower. A Geissler tube is composed of a sealed glass cylinder of various shapes, which is partially evacuated and equipped with a metal electrode at each end. It contains rarefied gases—such as neon or argon, air, mercury vapor, or other conductive substances, and sometimes ionizable minerals or metals like sodium. When a high voltage is applied between the electrodes, there is an electric current through the tube, causing gas molecules to ionize by shedding electrons. The free electrons reunite with the ions and the resulting energic atoms emit light via fluorescence, with the emitted color characteristic of the contained material.
A monoscope was a special form of video camera tube which displayed a single still video image. The image was built into the tube, hence the name. The tube resembled a small cathode ray tube (CRT). Monoscopes were used beginning in the 1950s to generate TV test patterns and station logos. This type of test card generation system was technologically obsolete by the 1980s.
A Crookes tube is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes and others around 1869–1875, in which cathode rays, streams of electrons, were discovered.
Amp is a music video program on MTV that aired from 1996 to 2001. It was aimed at the electronic music and rave crowd and was responsible for exposing many electronica acts to the mainstream. When co-creator Todd Mueller left the show in 1998, it was redubbed Amp 2.0. The show aired some 46 episodes in total over its 6-year run. In its final two years, reruns were usually shown from earlier years. Amp's time slot was moved around quite a bit, but the show usually aired late at night or in the early morning hours on the weekend. Because of this late night time slot, the show developed a small but cult like following. A few online groups formed after the show's demise to ask MTV to bring the show back and air it during normal hours, but MTV never responded to the requests.
In vacuum tubes and gas-filled tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission. This is in contrast to a cold cathode, which does not have a heating element. The heating element is usually an electrical filament heated by a separate electric current passing through it. Hot cathodes typically achieve much higher power density than cold cathodes, emitting significantly more electrons from the same surface area. Cold cathodes rely on field electron emission or secondary electron emission from positive ion bombardment, and do not require heating. There are two types of hot cathode. In a directly heated cathode, the filament is the cathode and emits the electrons. In an indirectly heated cathode, the filament or heater heats a separate metal cathode electrode which emits the electrons.
Rear-projection television (RPTV) is a type of large-screen television display technology. Until approximately 2006, most of the relatively affordable consumer large screen TVs up to 100 in (250 cm) used rear-projection technology. A variation is a video projector, using similar technology, which projects onto a screen.
A magic eye tube or tuning indicator, in technical literature called an electron-ray indicator tube, is a vacuum tube which gives a visual indication of the amplitude of an electronic signal, such as an audio output, radio-frequency signal strength, or other functions. The magic eye is a specific type of such a tube with a circular display similar to the EM34 illustrated. Its first broad application was as a tuning indicator in radio receivers, to give an indication of the relative strength of the received radio signal, to show when a radio station was properly tuned in.
David Cosman Nettheim, also billed as David Netheim, was an Australian character actor and theatre writer, he acted in radio, theatre and film, but was best known for his roles in numerous television series, both locally and in the United Kingdom
References
- ↑ "Lost UK TV Shows Search Engine". lostshows.com. Retrieved 2 April 2015.