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Feature article ELECTRONICS Inventors and their Inventions Note that many people independently invented the same thing; those who get the most credit were not necessarily the original discoverers. Also, many inventions represent the culmination of the work of many people. Some inventions are not necessarily the result of the labours of any specific individual but result from many contributions. We have tried to be as comprehensive as possible, but there will be inventions or inventors we have not been able to include in the available space. This series contains six parts. This first part, and the following three that will be coming over the next few months, will detail various individual inventors, usually with multiple inventions over a range of dates, organised by their birth dates. The last two parts will mostly cover inventions attributed to companies or other organisations, such as universities. We have endeavoured to use multiple sources to find accurate dates; dates often vary between sources, sometimes significantly. Here is our list of inventors by date of birth (up to 1804): Thales of Miletus static electricity Who laid the groundwork for modern technology? Modern inventions like transistors, ICs and wireless communications didn’t come out of thin air; thousands of brilliant scientists and inventors had to discover every aspect of the electronic technology that made them possible over the last few hundred years. Part 1: by Dr David Maddison W e tend to think of electronics as a relatively recent development. Transistors, ICs and many other keystone technologies of the current age were created from the late 1960s to the early 2000s. However, many important discoveries had to be made before any of that was possible. Modern devices like computer CPUs rely on principles that were discovered hundreds of years ago. We will look at the people behind those discoveries in this series of articles. The inventors and inventions described herein form the basis of all modern electronics. You may be surprised at how early some advanced concepts were conceived. Many modern devices were in26 https://unsplash.com/photos/_kdTyfnUFAc vented way ahead of their time. They often failed to find a use then, only to become very popular later. Many of the scientists and engineers described below contributed far more than we can describe in the space available. It was common to be a polymath (multi-disciplined) ‘back in the day’. We will focus on those areas of discovery and invention most relevant to electricity and electronics. c.624BCE-c.546BCE Described the generation of static electricity by rubbing amber, which caused it to attract feathers and other light materials. He also observed that lodestone, a form of magnetite naturally magnetised by lightning, could attract iron. Theophrastus pyroelectricity c.371BCE-c.287BCE Is said to have discovered pyroelectricity, the property of a material to temporarily become charged when heated and attract light materials like ash, similar to when amber is rubbed. William Gilbert electricity 1544-1603 Coined the term “electricus”, from which the word electricity is derived. He also explained that compasses worked because the Earth is a giant magnet with an iron core. He wrote a book in 1600 with the title “De Magnete”. You can read that book at www. gutenberg.org/ebooks/33810 He also invented the instrument Recent articles in Silicon Chip magazine on electronics tech. All About Batteries, January–March 2022; siliconchip.au/Series/375 The History of Transistors, March–May 2022; siliconchip.au/Series/378 IC Fabrication, June & July 2022; siliconchip.au/Series/382 Display Technologies, September & October 2022; siliconchip.au/Series/387 Computer Memory, January & February 2023; siliconchip.au/Series/393 Practical Electronics | January | 2025 The History of Electronics, part one Fig.1: Ebenezer Kinnersley’s ‘Electrical FIRE’ lecture notice. Source: Brown University Library (https:// library.brown.edu/dps/ curio/2013/05/). now known as the electroscope, which detects the presence of electric charge. Gilbert mistakenly did not believe electricity and magnetism were related; Hans Christian Ørsted and James Clerk Maxwell later showed them to be. Otto von Guericke electrostatic generator 1602-1686 He invented the first electrostatic generator, a sulfur sphere that could be rubbed to impart an electric charge to attract or repel objects. It inspired other, more advanced frictional generators. Christiaan Huygens wave theory of light 1629-1695 Developed the wave theory of light in 1690, which related to electric and magnetic fields. Francis Hauksbee the Elder modified electrostatic generator 1660-1713 Made a modified version of Otto von Guericke’s electrostatic generator in 1705, a partially evacuated glass sphere into which mercury was introduced. If rubbed to generate a charge, a glow was produced where the glass was touched. This led to the much later development of the gas discharge lamp, neon lighting and mercury vapour lamps. You can read his book “Physico-­mechanical experiments” at https://catalogue.nla. gov.au/catalog/3171279 Johann George Schmidt pyroelectricity unknown Observed in 1707 that the mineral tourmaline had a property we now know as pyroelectricity. Stephen Gray electrical conductivity 1666-1736 Discovered the principles of electrical conductivity and distinguished between conductors and insulators. He also made discoveries in electrical induction, imparting a charge into another object without contact. He received little credit for his discoverChristiaan Huygens also invented the pendulum clock. Source: https://w. wiki/7ATc Practical Electronics | January | 2025 Fig.2: Kinnersley’s “electric air thermometer” used a spark discharge to push water up a tube. Source: https://w.wiki/78sQ ies, but today, some know him as the “father of electricity”. Pieter van Musschenbroek Leyden jar / capacitor 1692-1761 Along with his student and a collaborator, he invented what became known as the Leyden jar in 1756, the original capacitor. It was used to store electrical energy produced by frictional generators. It consisted of a glass jar filled with water, a brass rod and another conductor. You can easily make a Leyden jar; see the video from ElectroBOOM at https://youtu.be/xjW-isgOijs and www.wikihow.com/Make-a-Leyden-Jar Ewald Georg von Kleist Kleistian jar 1700-1748 Invented the Kleistian jar in 1745, a form of Leyden jar. Benjamin Franklin lightning rods, glass harmonica etc 1706-1790 He named positive and negative charges in 1747. In 1748, he constructed a multi-plate capacitor with glass and lead plates. In that same year, he invented the “electric wheel”, a type of electrostatic motor that would run at 12-15RPM from a charge supplied by Leyden jars. In 1750, he showed that Leyden jars discharged more easily near a pointed rod, leading to the invention of lightning rods (also see Kinnersley’s entry). In 1752, he flew a kite in a thunderstorm to charge a Leyden jar attached to the wet string, proving that lightning was electricity. (The following two people who tried that were electrocuted.) In 1751, he published a series of pamphlets on electricity (pemag.au/ link/abnr). Carl Linnaeus pyroelectricity 1707-1778 Determined that pyroelectricity was a type of electricity in 1747. He later became known as Carl von Linné after being ennobled Ebenezer Kinnersley electric fire / electricity 1711-1778 Performed experiments with “electric fire”, as electricity was then called – see Fig.1. Benjamin Franklin described him as “an ingenious neighbor”. In 1748, he discovered that electricity passed through water. In 1751-2, he held a series of lectures about electric fire. In his March 1752 lecture, he suggested the lightning rod to protect structures from lightning before 27 Feature article Benjamin Franklin was one of the Founding Fathers of the USA. Source: https://w. wiki/7ATw Benjamin Franklin in 1748. It was incapable of useful work, but some call it the first electric motor. It consisted of a free-spinning star with angled, pointed ends that were charged from a power source. Ionised gas from the tips caused it to rotate. For more details, see pemag.au/ link/abn2 Franz Aepinus electricity and magnetism 1724-1802 He was the first to publish a treatise on electricity and magnetism (see his book at: pemag.au/link/abnu). Johan Carl Wilcke electrophorus Franklin did his kite experiment. In 1761, he wrote a letter to Franklin and, in 1763, published details of an “electric air thermometer” – see Fig.2. He demonstrated that electricity could produce heat. In 1761, he used electricity from Leyden jars to heat metals to incandescence, producing visible light, paving the way for the light globe. See “Expt. 11” in his letter to Franklin (pemag.au/link/ abp2). You can find instructions to make a “proof of concept” light globe on Hackaday: pemag.au/link/abnk 1732-1796 Invented the electrophorus, a device to produce static electricity, in 1762. Luigi Galvani bio-electricity 1737-1798 He is famous for discovering that frog’s legs will twitch with the application of an electric discharge from a charged Leyden jar. He also made the legs move with two differing metals that generated a current like a battery. Due to this early work in the field of bioelectricity, many modern electrical-­ related phenomena are named after Galvani. Alessandro Volta battery (voltaic pile) 1745-1827 He improved the electrophorus in 1775. Then in 1800, he invented what is now known as the voltaic pile or battery made of copper and zinc, using either saltwater or sulfuric acid electrolyte. He acknowledged the contributions of William Nicholson, Tiberius Cavallo and Abraham Bennet to his battery work. The unit of electrical potential, the volt (V), was named in his honour. He discovered by accident that a short circuit of his voltaic pile caused a copper wire to glow, confirming the principle of the incandescent light globe. Pierre-Simon Laplace Laplace transform 1749-1827 Developed the Laplace transform in 1785. It is used to solve differential equations, making it essential for circuit analysis. 1737-1806 Vasily Vladimirovich Petrov 1761-1834 Invented the “electrical whirl” (Fig.3), described in 1745 (pemag. au/link/abnt). It was an electrostatic reaction motor, also demonstrated by Invented the torsion balance, which enabled him to measure forces of attraction or repulsion between charged or magnetised bodies. Coulomb’s law states that the force between two electrically charged bodies is proportional Discovered the electric arc in 1802 after he built the world’s largest voltaic pile, comprising 4200 copper and zinc discs. In 1803, he proposed several uses for the electric arc, such as lighting, welding, metal processing etc. Fig.3: an electric whirl similar to the one invented by Andrew Gordon in 1745. This one is on display in the physics department of Washington and Lee University. Source: http:// physics.kenyon.edu/EarlyApparatus/ Static_Electricity/Electric_Whirl/ Electric_Whirl.html Fig.4: Wollaston’s improved battery with removable electrodes. Source: https://w.wiki/78sR Andrew Gordon electrostatic reaction motor 28 1712-1751 Charles Coulomb to the magnitude of their electric charge and the inverse square of the distance between them. This was known earlier, but it is named after Coulomb, as he was the first to publish it in 1785. The Coulomb (C) is also the unit of electric charge. Coulomb’s law / electric charge electric arc – welding Practical Electronics | January | 2025 The History of Electronics, part one William Hyde Wollaston 1766-1828 static electricity and electromagnetic induction Fig.5: an 1878 reproduction of one of Davy’s original arch lamps by Augustin Privat Deschanel. Source: https://w.wiki/78sS Demonstrated that static electricity was the same as from voltaic piles in 1801. He was said to have “accidentally” discovered electromagnetic induction 10 years before Faraday (who made the discovery in 1831) and made a failed attempt to build an electric motor. He built an improved type of copper/ zinc battery in which the electrodes were raised from the electrolyte when not in use, improving the life – see Fig.4. John Dalton atomic theory – materials 1766-1844 Contributed to atomic theory in ways that improved the understanding of conductors, insulators and semiconductors. Thomas Johann Seebeck thermocouples / thermopiles 1770-1831 Discovered in 1822 that a junction of two dissimilar metals produced a current. This is the basis of thermocouples, used to measure temperature, and thermopiles, which convert heat into electricity (such as radioisotope thermoelectric generators on spacecraft). Thomas Young expanded on wave theory 1773-1829 He expanded on the wave theory of light (first described by Huygens), vision and colour theory. André-Marie Ampère Amperè’s force law and solenoid 1775-1836 Set out to discover the relationship between electricity and magnetism. In 1820, Ampère’s friend, Dominique François Jean Arago, demonstrated the discovery of Hans Christian Ørsted that a current-carrying wire deflects a magnetised needle. Ampère determined that two parallel current-carrying wires would either attract or repel each other depending on the relative current directions and established Ampère’s force law. He invented the solenoid and had an idea for an electric telegraph. The SI unit for electric current, the amp (A), is named after him. Inspired by Ørsted, he also established Ampère’s righthand grip rule. Carl Friedrich Gauss ionosphere and electric telegraph 1777-1855 Popularised Gauss’ law in 1813, although it had already been discovered by Joseph Louis Lagrange in 1762. In 1839, he postulated that an electrically conducting region of the atmosphere, now known as the ionoPractical Electronics | January | 2025 sphere, reflected radio waves. The unit of magnetic induction, the gauss (G), is named after him. He had achievements in many other areas. He worked with Wilhelm Eduard Weber to develop an electric telegraph in 1833. Hans Christian Ørsted 1777-1851 Oersted’s law and right-hand thumb rule Discovered in 1820 that the needle of a compass would deflect near a current-­ carrying wire, establishing that an electric current had a magnetic field, the first connection between electricity and magnetism. He established Oersted’s (or Ørsted’s) law which states that an electric current establishes a magnetic field around it. That led to the “right-hand thumb rule”, which describes the relationship between a current and its magnetic field. A unit of magnetic field strength, the oersted (Oe), is named after him. Sir Humphry Davy 1st Baronet carbon arch lamp 1778-1829 Invented the carbon arch lamp, later renamed from arch to arc (see Fig.5), in 1802, 1805, 1807 or 1809 (depending on the source). He used charcoal sticks and a 2000-cell battery to strike an arc across a 100mm gap. The electrodes were originally horizontal, and the arc was shaped like an arch, hence the name. Arc lamps were widely used for street and commercial lighting from the 1870s until they were replaced by incandescent lighting from the early 1900s (except for specific applications like searchlights and movie projectors). Movie reels used to commonly be 2000ft (610m) long, with a runtime of about 22 minutes. That coincided with the life of carbon rods in pre-1970s theatre projectors. The projectionist would change the carbon rods at the same time as the reel. In 1801 or 1802, Davy also connected a piece of platinum across a 2000-cell battery, which caused it to glow, the basis for later experiments in incandescent lighting. Michael Faraday was Davy’s assistant from 1813 to about 1815, and occasionally helped him after that, such as with the Miner’s Safety Lamp. William Sturgeon electromagnet 1783-1850 Invented the electromagnet in 1824 – see Fig.6. It comprised 18 turns of copper wire on a lacquered iron Ushaped core, 30cm long and with a 13mm diameter. It was powered by a copper-zinc-acid battery. The cups contain mercury to make electrical connections. The magnet could support 4kg. Samuel Hunter Christie 1784-1865 “diamond method” (Wheatstone Bridge) Published the “diamond method” to compare resistances in 1833, a forerunner of the Wheatstone Bridge. Baron Pavel Schilling Schilling telegraph 1786-1837 Made numerous contributions to telegraphy and other areas. One of those inventions was the Schilling Fig.6: William Sturgeon’s electromagnet. Source: https:// w.wiki/78sT 29 Feature article telegraph, a type of ‘needle telegraph’ that sent a code along a series of wires to indicate the letter according to a binary code. His first telegraph was shown in 1828. It used only two wires with an innovative variable-length binary code to encode 40 letters. The current direction also varied, so two wires could give eight different states. He demonstrated another instrument with six wires in 1832. To transmit 40 different characters, six wires were needed for signalling, one for calling and one for a return. He abandoned the project because, from 1825, Czar Nicholas I of Russia opposed any form of mass communication and prohibited the public discussion of telegraphy. V² V ΩA² Ω Ω VA ΩW W A W V W A V Ω V² W W ΩA A² W Ω V A Fig.7: an Ohm’s Law wheel calculator. Source: https://w.wiki/78sV (CCSA-3.0). Conducted experiments with magnetism, mostly in 1823-1826. In 1824, he observed “rotary currents” or eddy currents. “Arago’s rotations” demonstrated interactions between a spinning non-magnetic conductor such as a copper disc and a magnetised body like a compass needle or magnet. In it, he detailed his theory of electricity, including the concept of resistance and what is now known as Ohm’s law – see Fig.7. In 1825, he used different lengths of wire (10cm, 41cm, 183cm, 315cm and 762cm) to produce different resistances, deriving Ohm’s law. It might be argued that he invented the resistor, although the concept of resistance was already known at the time. The unit ohm (Ω) is named after him. Sir Francis Ronalds Michael Faraday Dominique François Jean Arago 1786-1853 eddy currents electric telegraph 1788-1873 Produced the first working electric telegraph in 1816. It was not until two decades later that commercialisation happened. electromagnetic induction 1791-1867 Published “The Galvanic Circuit Investigated Mathematically” in 1827 – see pemag.au/link/abp3 Built a device to produce continuous “electromagnetic rotation”, now called the homopolar motor (Figs.8 & 9) in 1821, soon after Ørsted discovered electromagnetism. Faraday had discussed such a device with Sir Humphry Davy and William Hyde Wollaston, but failed to acknowledge them as contributing to his inven- Michael Faraday holding what is most likely ferromagnetic material. Source: https://w.wiki/7AUi Fig.8: two versions of a magnetic rotation apparatus, the first motor. On the left, the lower magnetic rod rotates about the centre, while on the right, the upper wire rotates about the centre magnet. The liquid is mercury. Source: Michael Faraday. Georg Simon Ohm Ohm’s law 30 1789-1854 tion, causing controversy. See: pemag. au/link/abn4 In 1831, Faraday discovered electromagnetic induction, demonstrating that a change in the magnetic field within a circuit induces an electromotive force (EMF) – see Fig.10. This discovery is the basis for electric power generation and led to the invention of the electrical generator and transformer. Joseph Henry independently discovered it in 1832, but Faraday published it first. In 1833, he published “Faraday’s laws of electrolysis”, introducing terms such as electrode, anode, cathode, electrolyte and ion. He observed that the resistance of silver sulfide decreased as its temperature increased, the first mention of what we now call a thermistor, a semiconductor with a strongly temperature-­dependent resistance. This was also the first observation of a semiconductor. The unit of capacitance, the farad (F), is named after him. Faraday also made numerous contributions in other areas; his theoretical work on the nature of the electromagnetic field led to the development of field theory in physics. Samuel Morse Morse Code 1791-1872 Developed the concept of the single-­ wire telegraph and invented Morse Code in 1840 (later enhanced by Alfred Lewis Vail). In developing the telegraph, Morse had a problem of limited range, which he solved with the help of Professor Leonard Gale, by adding relay circuits. Fig.9: a simple homopolar motor you can make with a battery, a length of wire, a neodymium magnet and a steel screw. Source: https://w. wiki/78sX (CC-BY-SA-2.5). Practical Electronics | January | 2025 The History of Electronics, part one + − Fig.10: an iron ring apparatus used by Faraday to observe electromagnetic induction. Momentarily completing the circuit on the left resulted in a momentary current on the right. Source: https://w.wiki/78sW Morse was contracted to build a 61km telegraph line between Washington, DC and Baltimore in 1843, which opened in 1844, with the first words transmitted being “What hath God wrought”. By 1850, 19,300km of telegraph lines had been laid across the USA. Morse’s 1840 telegraph patent can be seen at pemag.au/ link/abn6 The Morse Code standard today (still in use by some radio hams) is defined by ITU-R M.1677-1 and is based upon the work of Friedrich Gerke in 1848, which led to the International Morse Code of 1865. The hydrogen and oxygen produced were used in a form of stage lighting called limelight. The generator was also used for electric arc lighting and galvanising. The AC generated by the machine was converted to DC by a commutator. Johann Poggendorff slide wire potentiometer 1796-1877 Invented the slide wire potentiometer (variable resistor) in 1841. Around 1870, he also developed an electrostatic motor. Joseph Henry 1799-1878 electromagnet and mutual inductance Fig.11: Joseph Henry’s “intensity magnet”. Source: https://w.wiki/78sY motor based on a rocking rather than rotary motion (see Fig.12). The unit of inductance, the henry (H), is named after him; it is thought that Henry discovered inductance before Faraday, but Faraday published his findings first. Patented a magneto generator in 1850 for decomposing water by electrolysis. Improved upon Sturgeon’s electromagnet of 1824, in 1827, by using tightly wrapped silk-insulated wire rather than the uninsulated wire of Sturgeon – see Fig.11. This allowed Henry to use many layers of wire to make a more powerful magnet. He also discovered self-­induction and mutual inductance. In 1831, he made the world’s first commercial electrical product, a powerful electromagnet to separate magnetite from crushed ore (see the video at https://youtu.be/ru-daEOuUjs). Also in 1831, he developed the first electric Joseph Henry in 1879. Source: https://w.wiki/7AU$ Fig.12: Joseph Henry’s rocking beam electric motor of 1831. It pivoted in the middle with its ends in line with permanent magnets (C and D). As it rocked, electrodes contacted batteries at the ends (G and F), the magnet polarity reversed, and the beam would rock the other way. Source: https://siarchives. si.edu/collections/siris_sic_13161 Marcellin Jobard incandescent lighting 1792-1861 Suggested incandescent lighting in 1838, quoting É.M. Alglave and J. Boulard, “a small strip of carbon in a vacuum used as a conductor of a current, would emit an intense, fixed, and durable light”. His student, CharlesFrançois de Changy, commenced work on the idea in 1844. Floris Nollet magneto generator 1794-1853 Practical Electronics | January | 2025 Nicholas Joseph Callan induction coil and Maynooth battery 1799-1864 He invented the induction coil in 1836. It is a form of transformer driven by a pulsating direct current at about 20Hz using an “interrupter” to make and break the current flow. Despite not inventing it, Heinrich Daniel Ruhmkorff patented it in 1851 and then commercialised it. In 1848, he also commercialised the world’s largest battery at the time, the 31 Feature article Fig.13: the Maynooth battery. At the back is the zinc plate; in front of it is a porous ceramic pot. Both are inside the iron container, which forms the other plate. Source: Maynooth College Museum – pemag.au/ link/abp7 “Maynooth battery” (Fig.13) from iron and zinc, with 136L of acid and 577 individual cells. Back then, there was no way to measure voltage or current, so he measured the lifting capacity of an electromagnet to test its relative power. James Bowman Lindsay incandescent light globe 1799-1862 Invented the first incandescent light globe in 1835, enabling him to “read a book at the distance of 1½ foot”, but he never patented it and did not receive credit. In 1845, he suggested that telegraphy could work across water, including the Atlantic. He proposed welding to join the cables and sacrificial anodes for corrosion protection. Frederick Collier Bakewell fax machine 1800-1869 Demonstrated an “image telegraph” machine in 1851, an early fax machine and an improvement upon the system of Alexander Bain. The system worked by drawing on metal foil using insulating ink. The foil was rolled into a cylinder, and a stylus read the conducting and insulating areas, converting them into signals to be transmitted. The image was reconstructed on treated paper that electrical impulses could discolour. Keeping appropriate synchronisation at both ends was difficult, and the system was never commercialised. Moritz Hermann Jacobi’s law Fig.14: Jean-Daniel Colladon’s experiment demonstrating total internal reflection in a stream of water. Source: La Nature magazine, 1884. Also known as Boris Semyonovich (von) Jacobi, invented a process for making printing plates by electroplating in 1838. In 1839, he made an 8.5mlong battery-powered boat that carried 14 passengers. He studied electric motors and, in 1840, published the maximum power theorem or Jacobi’s law, which states that for maximum power transfer, the load resistance must match the source resistance. He also worked on the development of the electric telegraph during 1842-1845. Charles Wheatstone telegraph and Wheatstone bridge Fig.15: a replica of Weber’s electrodynamometer made in 1961. Source: https:// americanhistory. si.edu/collections/ search/object/ nmah_1273644 32 1801-1874 1802-1875 He performed an experiment in 1834 to determine the “velocity of electricity”. His result was about 50% too high. In 1837, Wheatstone also began work with William Fothergill Cooke on the telegraph. In 1843, he improved and popularised Samuel Hunter Christie’s “diamond method”, which became known as the Wheatstone Bridge. Jean-Daniel Colladon total internal reflection (TIR) 1802-1893 Demonstrated total internal reflection in a falling stream of water in 1842 (an experiment which can be done at home) – see Fig.14. This allowed optical fibres to be developed much later. The original idea was used to illuminate water fountains such as at the Paris World Exposition of 1889. Frederick de Moleyns 1804-1854 platinum filament incandescent light globe He obtained the first patent for an incandescent light globe in 1841. It used a platinum filament, although he also experimented with carbon filaments. Emil Lenz 1804-1865 Lenz’s law, resistive heating and electroplating Formulated Lenz’s law in 1834, which specifies the direction of a current induced by a magnetic field. He also independently discovered Joule’s law (or the Joules-Lenz law) in 1842, which describes how an electric current causes a conductor to heat, otherwise known as resistive or ohmic heating. He also participated in the development of electroplating with his friend Moritz Hermann. Louis Breguet Foy-Breguet telegraph 1804-1883 Developed a needle telegraph in 1842, the Foy-Breguet telegraph, used on the French railways and in Japan. In 1847, he suggested using finer diameter wires to protect telegraph wires against lightning strikes, the predecessor of the fuse. Wilhelm Eduard Weber electrodynamometer 1804-1891 Together with Carl Gauss, he built the first working electric telegraph, nearly 1.6km long, in 1831. Weber developed many sensitive devices for detecting and measuring electric currents and magnetic fields, including precise measurements of the Earth’s magnetic field. He also invented the electrodynamometer (Fig.15), a device that can measure current, voltage or power via the interaction of magnetic fields through two coils. This device was used to validate Ampère’s force law experimentally. The SI unit of magnetic flux, the weber (Wb), is named after him. For more on Weber, visit: pemag.au/link/abn7 Next month That’s all we have room for this month. The second article in this series, to be published next month, will continue the chronological list PE of early inventors. Practical Electronics | January | 2025