David Edward Hughes was born in London on 16th May 1831. His parents emigrated to the United States when he was seven, so his education included the physical sciences (called "Natural Philosophy") that were becoming increasingly important in the U.S. He was also an accomplished musician and toured extensively with the rest of the family, giving many public concerts. His musical ability attracted attention, and in 1850 he was appointed Professor of Music at Bardstown College, Kentucky. "Professor" would have been an honorary title for a nineteen year old.
Although employed to teach music, his work in physics got him an appointment as a teacher of Natural Philosophy at the college. In 1854 he left the academic world to go to Louisville and manufacture a printing telegraph he had devised. This device, which looked a lot like a small piano, printed letters out on a paper tape as they were received. This was a more efficient system than Samuel Morse's electric telegraph, patented in the same year. Hughes originally devised it as a means of copying music, but its use in telegraphy was to be more profitable. It proved successful in the United States after further development by George Phelps, and was taken on by the American Telegraph Company. The printers were mostly used in the larger offices, but they stayed in use until World War 2. They were progressively overtaken by teleprinters.
In 1857 Hughes took the printing telegraph to England to market it there. Initially the reception was unenthusiastic, but eventually it became well received in Europe and Hughes received a many honours and awards from European countries. He was financially secure on the income.
He extended his experiments to transmission of sound over wires. He discovered (or developed) the principle of loose contact transmitters, where a varying signal could be produced by acoustic pressure on a loosely connected group of conductors. He initially demonstrated this principle using ordinary iron nails lying across each other, connected to a battery and galvanometer. His work was published in 1878 in the Telegraph Journal and Electrical Review. He had by now refined his idea into the carbon pencil "microphone" that was the basis for many alternate transmitters in the days of early telephony. His research also covered the sensitivity of different forms of carbon and their suitability for varying sensitivities of his Microphone. Although his early published work details the effect of a single carbon pencil mounted in two carbon blocks, as shown, he also published comments on the use of multiple contacts ( he held that four contacts were required to transmit the human voice), and described acoustic feedback between the microphone and the transmitter.
Hughes was probably encouraged to publish by the patent caveat application lodged in the U.S. by Emile Berliner in 1877 for a loose-contact transmitter, and by Edison's patent application for a carbon transmitter. Edison supporters claim that Hughes developed or copied Edison's work. Because Hughes documented and demonstrated his early experiments and there were many witnesses to his microphone's efficiency, we have to give priority to Hughes.
Hughes probably gained some of his
inspiration from Philipp Reis, rather than Edison. He is reported to have tested
a Reis telephone during his 1865 visit to St. Petersburg. Hughes later commented
on those tests
"I was enabled to transmit and receive perfectly all musical sounds, and also a few spoken words, though these were rather uncertain, for at one moment a word could be clearly heard, and then from some unexplained cause no words were possible. This wonderful instrument was based upon the true theory of telephony, and it contained all the necessary organs to make it a practical success . . . . I also believe that the often successful transmission of words by Prof. Reis' transmitter was due to an accidental adjustment of his contacts to a true microphonic condition."
Hughes would have had no trouble obtaining a patent in Britain and some European countries for his microphone on the basis of his documentation. In these countries a patent was only issued to an invention that could be proved to work. In the U.S. an idea could be patented and developed later. It would have been a profitable patent but Hughes refused to apply, preferring to make his research publicly available for commercial development by others.
In later years Edison revealed that he had also read Reis' work, and was asked by the President of Western Union to improve on it. Because of the patent warfare going on at the time, it was unwise to admit this. With due credit to Edison, he later acknowledged this in his talks and lectures. Thus it appears that both men may have started independently from the same point, and reached similar conclusions.
Hughes became interested in the properties of magnetism and electromagnets. He designed and built the Induction Balance, a device whose principle led to the development of the mine detector (and eventually part of the coin detection and verification circuit in payphones). It was a loose connection in this device that led him to investigate what became known as radio waves. Towards the end of 1879 Hughes noticed that loose connections in his induction balance made them subject to "sudden electrical impulses, whether given out to the atmosphere through the extra current from a coil or from a frictional machine". The practical effect was that a sudden spike through the circuit could actually transmit some of the energy through the air and create a noise in a receiver some distance away. He used a tube of iron filings as a receptor, and a standard (homemade) telephone receiver. This was in fact one of the earliest demonstrations of the principle of radio transmission, using an arrangement that became known as a Coherer. He set up a clockwork generator to create spikes through the induction circuit, and was able to detect the spikes up to five hundred yards down the street.
In 1880 he demonstrated the equipment to members of the Royal Society. These eminent men, although prominent in various scientific fields, did not give it much importance. George Stokes dismissed it as simply caused by induction. Hughes, somewhat disappointed, continued to experiment on the idea privately. He did not publish his research. It was left to Heinrich Hertz to develop the concept of radio waves, publish the research, and receive the glory. Marconi went on to transmit Morse code using the radio wave and turn it into a commercial proposition.
Hughes died in London in January 1900. He was a rich, honoured and respected man, in contrast to so many other inventors of the time. The bulk of his estate, 470 000 pounds, was left to benefit four London hospitals, as well as bequests to scientific institutions for prizes and scholarships. He had married Anna Chadburn, an artist, and this lady ensured that Hughes' notebooks and papers were kept intact after his death. It is because of this that we are able today to verify just how advanced a scientist Hughes really was. The honorary title of "Professor" was well-earned. It is interesting to note that to this day many U.S. references claim Hughes as an American inventor rather than British.
Perhaps his most appropriate epitaph was in "The Electrician" on January 22, 1900.
"It is with profound sorrow that we have to announce the death, on Monday evening last, of Prof. D E Hughes. His death, at the age of 69 years, deprives the world of one of its most accomplished electricians, the electrical profession of one of its most honoured and respected members, and a worldwide circle of admirers of a genial and well beloved friend. It can truly be recorded that David Hughes lived without making a single enemy, and died mourned by all those whose good fortune it has been to come within the cheery circle of his friendship".
Hughes Prof. D "On The Physical Action Of The Microphone" , from "Journal of the Society of Telegraph Engineers and Electricians" 1883.
Allsopp F C "Telephones Their Construction and Fitting" 1917
Wedlake G E C "SOS - The Story Of Radio Communication" 1973
Amateur Mechanic & Work "Electric Bells and Telephones" 1926
Meyer Ralph O "Old Time Telephones - Technology Restoration and Repair" 1995
Herbert & Procter "Telephony Vol. 1" 1932
Website "Prof. David Hughes" http://chem.ch.huji.ac.il/~eugeniik/history/hughes.html
Website NNDB "David Hughes"
Dyer F L & Martin T C "Edison: His Life and Inventions" 1929.