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1882 __ The Phonopore
François van Rysselberghe (1846-1893)
Comment : This unusual phone was designed by Mr C Langdon-Davies of London in the mid 1880s. He drew on earlier work by Francois van Rysselberghe (1846-1893), who devised the principles used by the Phonopore. Van Rysselberghe was a Professor of Physics at the Industrial School of the Ostend School of Navigation. He was still in his teens during his early career, and established a reputation for brilliance. He designed a remote-reading weather station while attached to the Belgian Royal Observatory, and it was probably this that led him into the idea of superimposing a telephone signal across a telegraph line. He may have followed on original work done by David Hughes in Britain, published in 1879. Hughes proposed the use of a choke coil to reduce interference between telegraph circuits. Van Rysselberghe patented his system in 1882, and provided details of a number of circuits to handle different configurations of lines, both single-wire and full metallic (two wire). The system caught on rapidly in Europe, where most long-distance telephone lines used his system during the 1880s. Van Rysselberghe set out to provide a long-distance telephone using the existing telegraph networks owned by the various Post Offices. To do this, he needed to filter out the Morse signals from the voice, and the voice from the Morse. His timing was favorable. There were now many telephones in operation and the subscribers wanted to make longer-distance calls. The huge telegraph network was already in place. In Europe the telegraph networks were owned by the same State-owned Post Offices that owned the telephone trunk lines, so it was sensible that the trunk service be enlarged using the existing infrastructure. In Britain, W H Preece, the Post Office's Chief Electrician, held out on using the circuit not because of any of its own deficiencies but because the the Wheatstone high-speed telegraphy system used in Britain on the main telegraph lines may have had problems with it. In spite of this, it was eventually introduced anyway. It may have been the outcome of a visit by Preece to Paris in 1889, where he saw the system in action and was allowed to make tests on it. The following quotation is from Poole's The Practical Telephone Handbook , 1912 edition., and it should be noted that the BPO was still using Van Rysselberghe's circuits well into the 1930s. "By the inclusion in the battery and line circuit of high inductance coils in a telegraph line, as shown in the lower part of Fig. 516, the suddenness of the make-and-break telegraph currents can be so reduced that a telephone connected in a branch circuit of a single wire line would remain quite silent while telegraph messages were passing. As the telephonic speaking current will not affect the telegraph instruments, it was thus possible to work both telephone and telegraph on the same single-wire line, at the same time, quite independently. This system has been extensively used on the State telegraph lines in Belgium, and on a number of railway lines in other countries , and for call-wire circuits for trunk line working by the British Post Office.... By making the telephone return through a second telegraph line fitted in a similar manner (at both ends, of course) as shown in the upper part of Fig 516, it is easy to obtain an inductionless metallic circuit for the telephone. if the lines are properly balanced and twisted." Van Rysselberghe went to the United States in 1885 to test his system over longer lines, and was able to achieve a call from New York to Chicago, a distance of about 1000 miles. Unfortunately in the United States the situation was different to Europe. Western Union Telegraph and Bell Telephones had settled their legal differences, and part of the agreement was that they would stay out each others' business. This left Bell with the need to build their own long distance network from scratch, an expensive proposition. For this reason Van Rysselberghe's demonstration, although highly successful, did not draw much further attention. Bell could not provide a direct connection between the two cities until 1892. It was not until Pupin's invention of the loading coil many years later that Bell was able to provide true long-distance calls, and by then Van Rysselberghe's work had been forgotten. (Bob Estreich)
Urls : http://www.bobsoldphones.net/Pages/Phonopore/Phonopore.htm (last visited )

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