Bell, a Scot by birth, originally came to America as a professor of Vocal Physiology at Boston University, and became a United States citizen in 1882. He pursued wireless telephony with two devices. One was was his patented Photophone (Bell, 1880), the first successful wireless telephone, based on one of Steinhill's ideas. This device, depicted in Figure 4 (below), modulated a voice signal on a beam of light. The light beam was reflected off a delicately balanced mirror which was attached to the diaphragm of a microphone. When someone spoke into the microphone, the mirror moved slightly causing fluctuations in the beam. The receiver was a silvered parabolic reflector with a piece of selenium, a photoelectric element, in the center. The selenium cell would convert the light to electricity, and Bell used a telephone receiver as a transducer to convert the electrical signal back to sound (Bell, 1881). Although the Photophone achieved transmissions up to a mile and a half, it was little more than a novelty to be displayed at international expositions. Still, Bell system engineers continued to refine this device for another decade or so (Fagen, 1975, 362-363). French electrician E.J.P. Mercadier appropriated and refined Bell's idea in 1882 and called it the "Teleradiophone," reputedly the first use of the term radio to describe a wireless device (The Teleradiophone, 1882).

Trowbridge, however, would continue experiments for another ten years. He eventually concentrated on ship-to-shore transmissions using large induction coils, with the ultimate goal of building a wireless telegraph system to communicate with Europe. Trowbridge, the founder of the Jefferson Physical Laboratory, fully understood the works of Steinhill, Faraday, and Henry, but, like his contemporaries, paid little attention to Maxwell at this time. Nevertheless, he devised mathematical formulae to calculate both the inductive and conductive currents present in a circuit and differentiate between them (Trowbridge, 1880) and demonstrated that there was more to Edison's "etheric force" than electromagnetic induction (Trowbridge, 1875). By 1891, Trowbridge became thoroughly discouraged with the results of his experiments that indicated the practical limits of telephony by induction to be about a mile and a half, and only then with a primary coil of ten turns with a radius of 800 feet (Trowbridge, 1891b). In the process, Trowbridge experimented with an induction coil array which approximated tuned oscillators, as shown in Figure 5 (below), but he made no attempt to patent his experimental apparati nor profit from them.

Preece's fellow countryman, Willoughby Smith, an electrician with the Gutta Percha Corporation, had become interested in wireless by trying to solve problems that both conduction and induction create for wired telegraph transmission. Gutta Percha is a Malaysian latex which has a high resin content. As an insulator for electric wire, it is both more durable and watertight than rubber, and a better choice for underwater cable. So Willoughby Smith, an electrician who specialized in designing better cable, was very familiar with the crosstalk present from both ground conduction and induction fields, as described above. He learned to use these technologies to transmit primary signals, and developed a conduction wireless telegraph system similar to Preece's. Smith was able to sell his device to several lighthouse installations in Great Britain and Ireland (Fahie, 1899, 161-176). Smith also collaborated with Edison on the induction system used to communicate with moving trains (Fahie, 1899, 102-103). Up to his death in 1891, his experiments and inventions showed great promise.

Back in Boston, Professor Amos Emerson Dolbear of Tufts College, himself an early telephone inventor (Dolbear, 1877, 1879, 1881, 1886b), devised an elegantly simple wireless telephone, depicted in Figure 6 (below). He reportedly discovered this design when the wire connecting his laboratory telephone was disconnected, yet he was still able to transmit a signal by induction (Dolbear, 1882). At Preece's invitation, Dolbear demonstrated this device in London at the Society of Telegraph Engineers in 1882. The next year, he repeated it for the American Association for the Advancement of Science in Montreal and later received a patent (Dolbear,1886a). This device differs from all previous induction wireless inventions in that it adds an aerial condenser, or antenna, at both transmitter and receiver, and sends what we would now call a radio frequency (RF) signal (Hawks, 1927, 129-138;). With it, he could faithfully send a signal from his lab and receive it at his home, a distance of about half a mile (Dolbear,1886c). Unfortunately for Dolbear, he had no way to detect the RF signal, so his results were based solely on the inductance in the circuit, utilizing the magnetic field created by the coil attached to the transmitter. Dolbear never developed the idea commercially and later sold his patent to De Forest who used it in an unsuccessful attempt to prove patent priority over Marconi (Sivowitch, 1971,7).

While others were pursuing conduction and induction methods, Professor Heinrich Hertz, of the physics faculty at the Techniches Hochschule in Karlsruhe, Germany, was making practical applications of Maxwell's equations. In essence, Hertz proved in practice what Maxwell had demonstrated in theory, that electricity moved in waves radiated through the air (Appleyard, 1967, 114- 140; White, 1912, 93-102)). By 1888, after many years of experiments, he had published the results of his experiments, with descriptions of the apparatus involved, but it would be another five years before these papers were available in English translation. For those who could understand his work, Hertz provided a fresh set of ideas about wireless communication, perhaps the first since Steinhill, Morse, Faraday, and Henry. He grew gravely ill in 1892, and died less than two years later, a month before his 37th birthday.

It must be mentioned here that two others preceded Hertz in successful wireless experiments with electromagnetic waves. Professor Elihu Thompson, later a founder of General Electric, discovered these waves in 1875 during demonstrations in his classes at Philadelphia Central High School (Dunlap, 1944, 107). And David Hughes, the AngloAmerican inventor of the microphone, discovered similar phenomena in experiments conducted in England from 1879-1886. Several members of the Royal Society witnessed these experiments and discouraged Hughes from undertaking further work (Fahie, 1899, 305-316). Neither Thompson nor Hughes published the results of these experiments at the time.

Hertz's apparatus still lacked a suitable detector. French physicist Edouard Branly of the Institut Catholique in Paris supplied that with an invention he called the coherer. Branly began a study of the human nervous system about 1885 and discovered that the electrical impulses along the nerve fibers caused the neurons to mass together. He reasoned that the same principle should apply to powdered metal bombarded with electromagnetic waves and that he could build a device to investigate the properties of these waves (Blake, 1928, 63; Dunlap, 1944, 76-79). In the process, Branly created a sensitive detector, the missing element in Hertz's design, a discovery impressive enough to win Branly the Nobel Prize for Physics in 1921.

Another professor of physics, Augusto Righi of the University of Bologna, began an early replication and refinement of Hertz's experiments. Righi improved the oscillator and made the waves it generated more consistent and steady, which in turn made the signals easier to detect (Fahie, 1899, 192-194).

One more American electrician of note in the pre-Marconi era of wireless, was Nathan Stubblefield of Murray, Kentucky, who is perhaps more interesting for his story than for his inventions. Stubblefield was largely self-educated as his formal schooling ended at the age of 14 when his father died. He learned about electricity, telegraphy, and telephony by reading Scientific American and other publications at the local newspaper office (Stubblefield Papers). Although he was a farmer by trade, Stubblefield invented and patented an acoustic telephone (Stubblefield, 1888). He enjoyed modest success selling this device, and even a few franchises, until a competitor brought the superior Bell Telephone to the area. At this point, Stubblefield began to work on a wireless telephone design which he could sell to rural households outside the range of a wired system (Morgan, 1971, 45-72). He undoubtedly read about Dolbear, Trowbridge, Bell, and others, and by 1892 was demonstrating an induction telephone system to friends, with the primary coil wrapped around trees in his orchard and the secondary mounted in a nail keg. He also developed a conduction system and gave several well-publicized demonstrations in 1902 wherein he purposely transmitted a signal from one point to multiple receivers to show how his system could be used to disseminate news, information, and light entertainment (Fawcett, 1902). But Stubblefield was the victim of a stock fraud scheme, and it would be 1908 before he would patent his induction system (Stubblefield Papers). By then, it was as obsolete as the stagecoach featured in one of the patent illustrations (Stubblefield, 1908). Although he used inefficient technologies, conceptually Stubblefield developed wireless broadcasting, an idea that had not yet occurred to other electricians (Kahaner, 1980).

Then there is the enigmatic Nikola Tesla whose story embodies the intermingling of fact and fiction, phenomena and fantasy, science and folklore present in the pursuit of wireless during this era. A Serb born in Croatia, Tesla studied physics at the Austrian Polytechnic school in Graz, worked for the telephone exchange in Budapest and for Continental Edison in France and Germany, then came to America in 1884 to work for Edison and eventually became a U.S. citizen.

Tesla soon split with Edison over the subject of alternating current and set up his own laboratory in New York City. By 1893, he had created a device which would distribute electricity without wires, and demonstrated it publicly at the National Electric Light Association in St. Louis (Martin, 1894, 120-123). The unique features included a high powered (5kv) transmitter, transmitter and receiver tuned to a resonant frequency, and the use of a gas-filled tube as a receiver (Tesla, 1893, 318-327). When Tesla charged the transmitter, thirty feet away the receiving tube lit up (Cheney, 1981, 68-70; O'Neil, 1978, 130136).

Although analysis of the design indicates that it would transmit and receive RF, it is more likely that the fluorescent effect in the tube was due to conduction through the air, considering the short distance and high voltage involved (Marconi v. US. 1944, 68). Tesla patented this device (Tesla, 1900), and claimed that it could also be used to transmit intelligence, but he never developed the technology for electronic communication as Marconi did.

In 1901 Tesla began construction on the massive Wardenclyffe Tower on Long Island for radio transmission across the Atlantic, but later admitted to his financial backers that his true interest was in the wireless distribution of electric power. He ran out of money and never finished the tower (Cheney, 1981, 156-174; O'Neil, 1978, 203-211). In 1915, he launched a protracted legal action against Marconi over priority for the Italian's second American radio patent (Marconi, 1904). Tesla died in 1943, and later that year, the U.S. Supreme Court decided that although Marconi's original 1897 patent was valid, the Italian inventor had in fact appropriated Tesla's ideas, as well as those of Oliver Lodge and John Stone Stone, in his 1904 improvements (Marconi v. US, 1944).

In 1894, Sir Oliver Lodge conducted a wireless experiment before the members of the British Association in which he generated Hertzian waves with a Righi oscillator and detected them 150 yards away with a Branly coherer. He had also learned how to tune the transmitter and receiver to the same frequency. But neither Lodge nor his audience realized the significance of this demonstration, and he was too busy with his job as a professor to develop this system further (Vyvyan, 1922, 8-9).

Finally, there is the work of Alexander Popoff, the Russian, and Guglielmo Marconi, the Italian, who likewise put together the work of Hertz, Righi, and Branly to develop a revolutionary wireless telegraph design (Gibson, 1914, 50-64; Vyvyan, 1922,4-8). The two worked simultaneously but independently of each other, and in fact Popoff's demonstrations preceded Marconi's. But the Russian lacked the Italian's drive, connections, and luck, and his invention did not attract the interest of the Russian government (Hawks, 1927, 202-204). So it is Marconi, whose story is well known, who is called the inventor of the wireless device which led directly to radio (Barnouw, 1966, 19-24).

Marconi came from a wealthy Bologna family and was educated by private tutors. After he read an article about Hertz in an electrical journal, he became obsessed with the idea of using this device to signal across space. He read everything he could find about Hertz's and Branly's experiments, attended Righi's lectures, and by 1895 had built a working model of his wireless telegraph. Finding no interest in Italy, he took it to Great Britain where his mother, the daughter of a wealthy Irish distiller, had many contacts (Hawks, 1927, 220-228). There he met Sir William Preece who quickly realized the significance of Marconi's invention and its importance to British national and security interests, especially in communicating with ships at sea. Preece took up Marconi's cause, and by 1896, the Italian inventor had secured a British patent (Baker, 1976, 266280; Sterling and Kitross, 1978, 27). A year later, he received a U.S. patent as well (Marconi, 1897).

After Marconi's success, all significant developments in wireless would use the electromagnetic waves predicted by Maxwell and demonstrated by Hertz (White, 1912, 64-78).