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Feature Article The History of Electronics Inventors and their Inventions Physicist Isaac Newton wrote, “If I have seen further it is by standing on the shoulders of Giants”. The field of electronics is no different; we could not have the technology we have today without the contributions of thousands of brilliant people. This series of articles is about them. Part 3: by Dr David Maddison T he first two articles of this six-part series, published over the last last couple of months, listed significant electronics-­related inventions of individual inventors born before 1848. This part will cover individual inventors born from 1848 to 1881, while next month we will continue that list up to the recent past. The last two parts will discuss significant inventions credited to companies and other organisations. Inventors by date of birth (1848 to 1881): Shelford Bidwell photocells 1848-1909 Experimented with selenium photocells in the 1870s, and in 1880, reported how he also duplicated the “photophone” experiment of Alexander Graham Bell (https://pemag.au/ link/abnc). In another experiment, he used a selenium cell to scan an image and transmit it to another device via wires, which burned the reproduced image onto paper. He reported the results of his “Tele-­ Photography” in 1881 (https://pemag. au/link/abnd). He was the first to use a photocell to scan an image (Bain and Bakewell did not; see last month). He also invented a device that could scan an original document without redraw52 ing it on special media, analogous to a modern fax machine. In 1908, he published “Telegraphic Photography and Electric Vision” (https://pemag.au/link/abne), on transmitting motion video (ie, TV) and the large amount of data involved. Chichester A. Bell tape recorder 1848-1924 Bell and Sumner Tainter (1854-1940) received US patent 341,214 in 1886 for a recording and playback device where sound was recorded on a waxcoated paper strip in a reel-to-reel arrangement. It was the earliest tape recorder, but was considered inferior to Edison’s wax cylinder for recording and playback and was not commercially released. Sir John Ambrose Fleming 1849-1945 thermionic valve, trans-Atlantic transmission Invented the first thermionic valve, otherwise known as a “vacuum tube”, in 1904 (see Fig.29). Fleming called them oscillation valves “for the rectification of high-frequency electric oscillations as used in wireless telegraphy”. They were diodes, the simplest type of valve. Fleming’s valve is considered the beginning of electronics because it was the first active electronic component. As radio detectors, Fleming’s valves were not more sensitive than crystal detectors. However, they did not need Fig.29: Fleming’s first vacuum tube diodes from 1904. Source: https://w.wiki/7DAU Practical Electronics | March | 2025 The History of Electronics, part 3 constant adjustment for use on ships due to the movement like crystals did. In 1899, Fleming, under contract from Marconi, designed the first highpower radio transmitter, much larger than the 200-400W transmitters used by Marconi. It was a spark-gap transmitter powered by a 25kW alternator and it performed the first trans-­Atlantic transmission in 1901, over 3500km, which was credited to Marconi despite Fleming’s involvement. Charles Fritts 1850-1903 solid-state solar cells He made the world’s first solid-state solar cells in 1883 with selenium and a thin layer of gold. They had an efficiency of 1%, making them too expensive and inefficient for generating power, but they were used as light sensors for cameras and in other applications into the 1960s. Oliver Heaviside mathematical equations, E region etc 1850-1925 Reformulated and simplified Maxwell’s equations to make the Maxwell-­ Heaviside equations and put them in their modern form. He also invented the Heaviside step function to calculate the current drawn when an electrical circuit is switched on, and developed transmission line theory (or telegraphers’ equations). The latter increased the transmission rate of the trans-Atlantic telegraph cable ten times, to one character per minute. He discovered that telephone line transmissions could be improved by a series inductance in the cable. He and Arthur Edwin Kennelly (1861-1939) independently predicted the presence of the Heaviside layer, Kennelly-­ Heaviside layer or E region, part of the ionosphere that reflects medium-­ frequency waves. William Edward Sawyer electricity distribution 1850-1883 Sawyer worked on telegraphy and electric lighting. With Albon Man, he founded the Electro-Dynamic Light Company (1878-1882), later purchased by Westinghouse, to provide lighting and distribute electricity into cities. His lighting system contained a safety switch and a current regulator. His company had patents dated 1877 and 1878 for incandescent lights, predating Edison. Sawyer’s lights were not long-lasting, a problem he never solved. Karl Ferdinand Braun 1850-1918 cathode ray tube (CRT), oscilloscope etc He discovered the rectifying properties of a metal-semiconductor junction (schottky diode) in 1874, using mercury as the metal and copper sulfide or iron sulfide as the semiconductor. He also invented the cathode ray tube and the oscilloscope in 1897. He worked on wireless telegraphy and invented a crystal detector in 1898, among other contributions. In 1905, he devised the phased array antenna. Edward Weston 1850-1936 Weston Cell, Constantan & Manganin alloys Invented the Weston Cell in 1893, a highly-stable electrochemical cell used as a voltage reference. It was the international standard for EMF from 1911-1990. He invented the all oy Constantan in 1887, which has a low variation in resistivity with temperature, used in thermocouples, and Manganin in 1892, with almost no variation in resistivity with temperature, used in precision resistors. In 1888, he founded the Weston Electrical Instrument Corporation, which became famous for the wide variety of high-quality electric meters it manufactured. Sir Oliver Joseph Lodge moving-coil loudspeaker etc 1851-1940 Lodge identified electromagnetic radiation independent of Hertz. He also made an improved Hertzian wave detector based on metal filings in a tube he named a “coherer”, based on Branly’s earlier work (see last month). Under the influence of a radio signal, the conductivity between the two electrodes would change. The device had to be regularly tapped to restore its sensitivity. It was used until 1907, when Marconi’s crystal detector replaced it. He also invented the moving-­coil loudspeaker in 1898. In 1898, he invented and patented “syntonic tuning” to tune radio equipment to specific frequencies, causing a patent dispute with Marconi. He developed a form of electric spark ignition for internal combustion engines. Emile Berliner 1851-1929 microphone, Berliner Gramaphone Record Developed an improved type of tele­ phone transmitter (microphone); his patent was acquired by the Bell Telephone Company. It was contested by Thomas Edison, who won the case. There were many expensive and complicated court cases in the USA in the 1870s and 1880s contesting the invention of the telephone; see https://w. wiki/7DYJ In 1887 and 1888, Berliner received US patents 372,786 & 382,790 for the “Berliner Gramophone Record”. They were flat discs, like the records we know today, although the Berliner records were only 18cm in diameter, played two minutes per side and rotated between 60RPM and 75RPM. They competed against wax cylinder recordings. There is a project to put about 18,000 Berliner recordings on Flickr: https:// pemag.au/link/abpa Leonardo Torres y Quevedo 1852-1936 “Telekino” remote control, El Ajedrecista game Quevedo demonstrated a remote control he invented in 1903, called the “Telekino” (Fig.30). It was remarkably advanced for the time and was the second remote control invented after Tesla’s in 1898. 19 different commands could be sent, with the command Karl Ferdinand Braun was a founder of Telefunken. Source: www. cathodique.net/ FBraun.jpg Fig.30 (right): the Telekino receiver in the Torres Quevedo Museum in Madrid, Spain. Source: https://w. wiki/7DAV Practical Electronics | March | 2025 53 Feature Article sequence recorded. He tested it with dirigibles in 1901. In 1905, he demonstrated the device with a three-wheeled vehicle, and in 1906, a boat with people onboard. The work was abandoned due to a lack of money. He also invented what was arguably the first computer game. It was called “El Ajedrecista” and could play certain chess moves (see Fig.31). Mechanical arms moved pieces while sensors detected the opponent’s moves. It still works today and can be seen at the Torres Quevedo Museum in Madrid. Temistocle Calzecchi-Onesti experiments leading to the coherer Fig.31: the remarkable El Ajedrecista chess-playing machine. Source: www. torresquevedo.org/LTQ10/images/ PrimerAjedrecista.jpg (CC BY-SA 3.0). Conducted experiments from 1884 on the electrical conductivity of tubes of metal filings and how they were affected by various electrical influences. This led to Branly’s invention of the coherer (see Lodge’s entry on page 53). Heike Kamerlingh Onnes superconductivity 1853-1926 Jonas Wenström spark gap transmitter, radio waves 1855-1893 Received a Swedish patent for a three-phase electrical system in 1890. He developed it independently of Mikhail Dolivo-Dobrovolsky (see his entry on page 56). Hall effect 1855-1938 He discovered what is now known as the Hall effect in 1879, the basis of modern magnetic field detectors and Hall thrusters on spacecraft. It explains that a voltage is produced at right angles to a current flow in a conductor with a magnetic field perpendicular to the current flow – see Fig.32. Paul-Jacques Curie piezoelectricity 54 1856-1940 Contributed to atomic physics. In 1893, he proposed the acoustic waveguide, and in 1894, Oliver Lodge experimentally verified it. In 1897, Thomson suggested the existence of the electron. He also conducted experiments with cathode rays. Edwin Herbert Hall Fig.33: Hertz’s 1887 spark-gap transmitter, with an induction coil, dipole antenna, capacitance (C) at the ends, a spark gap (S) and resonant loop antenna receiver with a spark micrometer (M) to measure signal strength. It operated at around 50MHz. Source: https://w. wiki/7DAW (CC-BY-SA-3.0). Sir Joseph John Thomson He discovered superconductivity in 1911 (the loss of all electrical resistance of some materials at certain low temperatures). It is used to generate powerful magnetic fields in machines like MRI scanners. High-temperature superconductors with less stringent cooling requirements are currently being developed. three-phase electrical system Fig.32: the operation of a Hall effect IC. Original source: www.ablic. com/en/semicon/products/sensor/ magnetism-sensor-ic/intro/ 1853-1922 than one phase) and associated induction motors, licensed by Westinghouse in 1888. From 1890, he tried to develop a wireless lighting system using Geissler tubes powered by a Tesla coil he invented in 1891. He was photographed at his Colorado Springs facility in 1899 with the “magnifying transmitter” Tesla coil (done using double-exposure; see the lead image). It produced 12MV 150kHz arcs up to 41m long with an input power of 300kW. In 1893, he consulted on the design of a Niagara Falls hydroelectric power station. In 1898, he developed the first wireless radio remote control for a boat, a concept he called teleautomatics. In 1906, he demonstrated a bladeless turbine for a power station, which spun at 16,000RPM and produced 150kW. The unit of magnetic flux intensity, the tesla (T), is named after him. 1855-1941 With his brother Pierre Curie (18591906), discovered piezoelectricity (used for guitar pickups etc) in 1880. They also studied pyroelectricity. Nikola Tesla 1856-1943 polyphase electrical system, Tesla coil etc Tesla was a prolific inventor and genius. He developed the polyphase electrical system (AC power with more acoustic waveguide Heinrich Rudolph Hertz 1857-1894 Hertz proved the existence of radio waves, first predicted by Maxwell’s equations, from 1887 onward. He demonstrated properties such as polarisation, reflection and standing waves. In 1887, he also built the first spark gap transmitter (Fig.33). The unit of frequency, the hertz (Hz), is named after him. William Stanley Jr 1858-1916 AC transformer and complete AC system Built the first practical AC transformer in 1885 based on the prototype of Gibbs and Gaulard; see US patent 349,611. In 1886, he demonstrated a complete AC system with generators, transformers and high-voltage transmission lines in Great Barrington, Massachusetts, lighting offices and stores. Sir Jagadish Chandra Bose 1858-1937 millimetre waves, microwave components etc He produced millimetre (5mm wavelength) 60GHz electromagnetic waves in 1894 because they were a more convenient size to work with in his small laboratory – see Fig.34. In 1895, he showed that millimetre Practical Electronics | March | 2025 The History of Electronics, part 3 Fig.34: 60GHz microwave apparatus by Jagadish Bose. The galvanometer and battery are modern. The transmitter on the right generates microwaves from sparks between tiny metal balls. Above the galvanometer is a galena point-contact detector inside a horn antenna. Source: https://w.wiki/7DAY (CC-SA-3.0). waves could go through the human body and walls, achieving a range of 23m. Bose was not interested in patenting or commercialising his amazing work, although he was persuaded to patent a metal-­semiconductor diode in 1901, awarded in 1904 (US patent 755,840). He developed a galena semiconductor crystal microwave detector and many other now-familiar microwave components, such as waveguides, horn antennas, dielectric lenses and polarisers. Much of his equipment can be seen at the Bose Institute Museum in Kolkata, India (www.jcbose.ac.in/ museum). Nobel laureate Sir Neville Mott said that Bose was 60 years ahead of his time and that he had antici- pated p-type and n-type semiconductors. One of his concepts from a paper he wrote in 1897 was used in the 1.3mm multibeam receiver of the National Radio Astronomy Observatory (NRAO) 12m telescope in Tuscon, Arizona. Friedrich August Haselwander 1859-1932 electric arc lamp Invented an electric arc lamp in 1880, and in 1887 invented and put into service a synchronous threephase generator in Europe (Fig.35). It developed about 2.8kW at 960RPM and 32Hz. Aleksandr Popov lightning detector (radio receiver) 1859-1906 Popov built a wireless lightning detector in 1895 (see Fig.36), one of the first radio receivers, and in 1896 transmitted radio signals over 250m. Some of his work was based on the findings of Sir Oliver Joseph Lodge. In 1898, he performed ship-to-shore communication using wireless telegraphy over 10km, and in 1899, 48km. In ex-USSR countries, the 7th of May is celebrated as Radio Day, the day Popov first demonstrated his lightning detector. Herman Hollerith punch(ed) cards 1860-1929 Developed punched cards for data storage and analysis, used in the 1890 US Census. These evolved into IBM punched cards, used as late as the early 1980s. See Silicon Chip magazine’s January 2023 article on Computer Memory for more on punched/punch cards (siliconchip.au/Series/393). Ottó Titusz Bláthy 1860-1939 modern transformers, voltage regulator etc Sir Jagadish Bose demonstrating the horn antenna. Source: https://w. wiki/7DuL Fig.36: Alexander Stepanovich Popov’s 1895 “coherer receiver”, one of the first radio receivers, designed to detect lightning strikes. Key: A) antenna, B) bell, C) coherer (detector), E) electromagnet, G) ground, L) chokes for noise immunity, R) relay, V) battery. Source: https://w. wiki/7DAa Practical Electronics | March | 2025 Fig.35: Haselwander’s three-phase generator with stationary ring armature and four-pole rotor, as displayed in 1891 at the International Electrotechnical Exhibition in Frankfurt. Source: https://w. wiki/7DAZ Bláthy, Károly Zipernowsky (18531942) and Miksa Déri (1854-1938) applied for a patent for the first modern transformers in 1885, which were much more efficient than the designs of Gaulard or Gibbs. The trio also designed the first power station with AC generators “to power a parallel-­ connected common electrical network”. Bláthy also invented the voltage regulator, AC watt-hour meter (1889), motor capacitor for single-phase AC motors and turbo generator for steam power plants. Paul Julius Gottlieb Nipkow Nipkow disc 1860-1940 Invented the Nipkow disc in 1883. It was a disc with a spiral pattern of holes to divide a picture into a linear series of points to enable opto-electronic 55 Feature Article Paul Gottlieb Nipkow is considered to be one of the fathers of television. Source: https://w. wiki/7DuZ imaging of an object. There was little interest at the time. It became the basis of the first electro-­ optical television systems in the 1920s30s (see Silicon Chip magazine’s articles on Display Technologies in the September & October 2022 issues for more siliconchip.au/Series/387). Peter Cooper Hewitt 1861-1921 mercury vapour lamp, mercury arc rectifier He invented the mercury vapour lamp in 1901, the predecessor of the fluorescent lamp. In 1902, he invented the mercury arc rectifier, the first commercially available non-mechanical rectifier. In 1916, he was involved in developing the Hewitt-Sperry Automatic Airplane, the predecessor of the cruise missile. Mikhail Dolivo-Dobrovolsky asynchronous three-phase motor 1862-1919 Invented an asynchronous threephase motor in 1888, which had low torque at low speeds. This problem was solved with a variation of that motor, the slip-ring motor, with high torque at low speeds in 1891. He also developed the delta-wye transformer for threephase distribution systems in that year. would be solved by electronic systems with CRTs at both ends. Walther Hermann Nernst Nernst (incandescent) lamp 1864-1941 Invented the Nernst lamp (Fig.37) in 1897 as an improvement to the incandescent lamp. The way it works is very interesting. An element heats a ceramic rod made of zirconium oxide and yttrium oxide. The rod’s resistance decreases as it heats up and the heating element is turned off. A current sustains the glowing ceramic rod due to ohmic heating. It can operate in the air, as the ceramic rod will not degrade like a metal filament. They are obsolete as a visible light source but are still used as an infrared light source in spectroscopy, as they emit infrared over a wide range of wavelengths. See the video titled “The Nernst Lamp” at https://youtu. be/1vCQySb6ulA Charles Proteus Steinmetz Steinmetz’s equation 1865-1923 He contributed to AC hysteresis theory from 1890 and solved practical problems with heat build-up in AC motors. This resulted in him building a powerful motor for Otis Elevators to reach higher floors. His work led to Steinmetz’s equation for calculating losses in magnetic core materials, published in 1892 (see the PDF at https://pemag.au/link/abnf). 56 1866-1932 He first transmitted speech by radio in 1900 and made the first two-way radiotelegraphic communication across the Atlantic in 1906. He invented an electroacoustic transducer called the Fessenden oscillator in 1912, and in 1914, it detected icebergs 3km away. It was also used for underwater telephony and depth sounding. For more information on that, see Sililcon Chip magazine’s June 2019 article on Bathymetry (siliconchip.au/ Article/11664). Marie Curie mobile X-ray machine 1867-1934 Invented the mobile X-ray machine in around 1915, powered by a dynamo. Henri Abraham astable multivibrator 1868-1943 He and Eugene Bloch (1878-1944) invented the astable multivibrator. The work was done during WW1 but published in 1919. He made the first measurements of the speed of electromagnetic propagation between 19111914 and developed the first French triode valve. Worked in telephone technology and radios. In 1890, he started work on a mathematical analysis of telephone links for American Bell Telephone Co. In 1900, he developed “selective fourcircuit tuning” for radios to improve their selectivity and reduce noise. Lenard began investigations of cathode rays in 1888 and developed a modified Crookes tube with what was to become known as a “Lenard window”, a thin aluminium window that made it possible to study the radiation from outside the tube. Boris Lvovich Rosing early television 1863-1930 Alan Archibald Campbell-Swinton experimented with cathode ray tubes (CRTs) in 1903 for transmitting television images. Prompted by Shelford Bidwell, on the 18th of June, 1908, his letter in Nature entitled “Distant Electric Vision” (https://pemag.au/link/abpb) said the problems of mechanical television radio, sonar etc 1869-1943 telephone links, selective four-circuit tuning 1862-1947 Lenard window (aluminium) for Crookes tube transmitting television images Reginald Aubrey Fessenden John Stone Stone Philipp Lenard Alan Campbell-Swinton He worked on AC circuit theory and analysis, which he greatly simplified from previous methods, announcing his findings in 1893. He also investigated AC transient theory and other transient phenomena, such as lightning bolts. Fig.37: a Nernst lamp, an early form of incandescent light. Source: https://w.wiki/7DAb 1869-1933 He started considering ideas of what we now know as television in 1897, but he called it the “electric telescope”. His approach for the receiver was purely electronic, using a CRT, unlike other ideas for television around that time that were mainly mechanical. By 1902, he made a device that could draw a basic figure on a CRT. Instead of a slow-reacting selenium cell detecting light for the camera, he used a fast-reacting photocell onto which the image was projected by a rotating mirror system. He obtained patents for his invention in 1907 and 1911. It was presented Practical Electronics | March | 2025 The History of Electronics, part 3 Fig.38: Valdemar Poulsen’s magnetic wire recorder, invented in 1898. Source: https://w.wiki/7DAd (CC-BYSA-2.5). in Scientific American, 1st of April, 1911: https://pemag.au/link/abng Valdemar Poulsen magnetic audio recordings 1869-1942 Successfully implemented the first means to magnetically record audio in 1898 by magnetising wire along its length (Fig.38). There was no amplification, so the recording was faint but audible with headphones. The device was called the Telegraphone and had limited commercial success due to its low volume and complexity. With his assistant, Peder Oluf Pedersen, he developed other recording devices using tape and discs. In 1903, he also invented the Poulsen Arc Transmitter (Fig.39), widely used as a radio transmitter in the early 1920s before vacuum tubes were developed. Arthur Korn fax machines 1870-1945 Korn pioneered the modern fax machine, which he used to transmit photographs. He used light-sensitive selenium cells in his “phototelautograph” or “Bildetelegraph”. In 1906, he sent a photo of Crown Prince Wilhelm over 1800km via the telegraph network. In 1913, he transmitted a movie recording, although the specifics are unclear. We assume it was a frame-byframe transmission. In 1923, German police used Korn’s system to transmit photos and fingerprints. Paul Langevin ultrasound transducer 1872-1946 Invented the first ultrasound device in 1917, the quartz sandwich transducer for submarine detection. William David Coolidge making tungsten ductile 1873-1975 Fig.39: a 1919 Poulsen arc transmitter from a US Navy radio station with a continuous power rating of 500kW (1MW short-term). Source: https://w.wiki/7DAe making tungsten ductile, allowing it to be drawn into filaments for light globes. The globes were sold by General Electric from 1911. Marconi’s radios were important in rescuing survivors of the RMS Titanic (1912) and RMS Lusitania (1915). Lee De Forest tungsten filament light globe 1873-1961 three-element triode, recording audio Invented a three-element triode thermionic tube in 1906, the “grid Audion” (Fig.40), for use as an amplifier and an oscillator. This invention is regarded as the start of the Electronic Age. In 1919, he patented the DeForest Phonofilm system for optically recording audio waveforms onto movie films. Guglielmo Marconi 1874-1937 wireless transmission, spark gap transmitter etc Guglielmo Giovanni Maria Marconi built a device to receive radio waves produced by lightning in 1894. That year, he also demonstrated wireless transmission to ring a bell across a room. He developed a spark gap transmitter and coherer receiver. A coherer was a glass tube with metal filings that radio waves caused to become closer together and therefore more conductive. In 1895, he designed a system that could transmit over 3km. By 1896, he had transmitted over 6km, then 16km. In 1899, he transmitted across the English Channel. In 1907, he established a commercial trans-Atlantic telegraph service. Just Sándor Frigyes 1874-1937 Also known as Alexander Friedrich Just, he and Franjo Hanaman (18781941) were the first to invent an incandescent light globe with a tungsten filament in 1904. They were brittle due to the way they were made, although they lasted longer and were very efficient compared to carbon filaments. They licensed their patent to the Tungsram company (which also licensed Bródy’s patent for using krypton gas in globes in 1934). In 1904, they applied for a Hungarian patent and, in 1905, applied for US Patent 1,018,502. The tungsten filament globe became practical with the invention of Coolidge’s fabrication method for tungsten filaments. Alexander M. Nicholson crystal oscillator unknown Invented the first crystal oscillator in 1917 using Rochelle salt, a piezoelectric material, and filed for US patent 2,212,845 in 1918. Walter Guyton Cady quartz crystal oscillator 1874-1974 He invented a quartz crystal oscillator in 1921 and realised that such devices could be used as frequency standards. He filed US patents in 1921 (1,472,583) and 1937 (2,170,318). Fig.40: an early grid Audion, invented in 1906, which many regard as indicating the start of the electronic age. Source: https://w.wiki/7DAf (GFDL-1.2). Coolidge developed a method for Practical Electronics | March | 2025 57 Feature Article Édouard Belin Bélinographe, image transmission 1876-1963 Invented the Bélinographe, which used a photocell to scan and transfer press photos (see Fig.41). It was developed in 1907 and first used commercially in 1913-1914 to transmit pictures over dedicated leased telephone lines. Later models could use ordinary telephone lines. In 1921, a version was used to transmit a photo by radio across the Atlantic. By 1926, RCA was using it to transmit Radiophotos. Miller Reese Hutchison 1876-1944 electronic hearing aid, tachometer, Klaxon He developed the first commercial electronic hearing aid in 1898 (going to market in 1899), with a carbon microphone he called the “Akoulallion”. In 1900, he developed a portable battery-­ powered device that he called the “Akouphone”, then the Acousticon 1 in 1902. For more details, see https:// pemag.au/link/abnl In 1908, Hutchison invented an electric tachometer for ships and the Klaxon in 1910. Robert Von Lieben triode with control grid 1878-1913 Lieben, with engineers Eugen Reisz and Siegmund Strauss, invented the gas-filled (low vacuum) triode with a control grid in 1910. It was the first thermionic valve designed for amplification rather than demodulation and was used as a telephone repeater. Ernst Alexanderson Alexanderson alternator 1878-1975 Ernst Frederick Werner Alexanderson invented the Alexanderson alter- nator in 1904. It produced radio waves more efficiently and with a narrower bandwidth than the spark-gap transmitters used until that time, and it could deliver them continuously at high power. Alexanderson alternators were used to transmit long-wave radio communications from shore stations from 1906 to the 1990s, although they were too big and heavy for most ships. The first commercial model would generate a frequency of 100kHz and had a power rating of 50kW. The last transmitter in regular use was Grimeton Radio Station in Sweden, which was used until 1996 and is occasionally used today (see page 17 of Silicon Chip’s March 2023 issue). Albert Einstein 1879-1955 theory of relativity, photoelectric effect which was used as an amplifier and low-frequency oscillator. The latter is still used in microwave ovens (albeit in a modified form; see the entry for Russell Harrison Varian next month). Louis Blattner Blattnerphone 1881-1935 Blattner, under license by Kurt Stille (1873-1957), produced a new audio recorder using steel tape instead of wire called the “Blattnerphone” in 1925. It was also based on the magnetic recorder of Valdemar Poulsen (see his entry on page 57). In 1933, the Marconi Company acquired the rights to the Blattnerphone and made an improved version called the Marconi-Stille recorder, which the BBC used from 1935 into the 1940s (Fig.42). Irving Langmuir 1881-1957 Published his theory of relativity in 1905. Relativity must be considered in operating satellite navigation systems such as GPS and many other applications. He also explained the photoelectric effect in 1905, expanding on the work of Planck, which went on to be used in night-vision devices, among others. Improved the vacuum pump, which led to high-vacuum rectifiers and amplifier tubes. He, along with Lewi Tonks, also discovered that an inert gas improved the lifetime of incandescent globes. He also found that twisting a tungsten filament enhances efficiency. Alexander Behm magnetic tape for sound recording echo sounding, Echolot 1880-1952 He invented echo sounding in 1912 to measure water depth and detect obstacles, obtaining a patent in 1913. In 1922, he produced the Echolot to measure water depth beneath a ship. Albert W. Hull dynatron vacuum tube, magnetron 1880-1966 Invented the dynatron vacuum tube in 1918 and the magnetron in 1920, vacuum pump improvements Fritz Pfleumer 1881-1945 He invented magnetic tape for sound recording in 1927 and received a patent for it in 1928. He used paper and iron oxide, with lacquer as an adhesive to bind the oxide to the paper. In 1932, he granted rights to this invention to AEG. They used it with the first practical tape recorder, the Magnetophon K1, demonstrated in 1935. Cpt Henry Joseph Round LEDs, vacuum tubes 1881-1966 He contributed to vacuum tube development and developed a triode around the same time as Lee de Forest. He discovered feedback in vacuum tubes independently of Alexander Meissner and Edwin Armstrong. He made the first report of what we now know to be a light emitting diode (LED), utilising ‘cat’s whisker’ detectors, the first type of semiconductor detector, made of silicon carbide and producing faint yellow light. Next month Fig.41: the Bélinographe used a photocell to scan and transfer photos in 1907. Source: https://w.wiki/7DAk 58 Fig.42: the Marconi-Stille tape recorder. Source: Birmingham Museums Trust – https://w.wiki/7Dup (CC-BY-SA-4.0). That’s all we have room for in this issue. As mentioned earlier, we will pick up where we left off in the fourth article next month, finishing our chronological list of inventors. We will then turn to discoveries credited to groups of people. PE Practical Electronics | March | 2025