The telephone is a much younger invention than the telegraph. Fifty telegraph companies were alreadv operating in the United States alone, when the French mechanic Charles Boursel first suggested the idea of transmitting speech electrically. The first to put his idea into practice was the German Philipp Reis, but his telephone was too primitive to find practical application. A telephone that did find application was invented by the American Graham Bell. On March 10, 1876, he made an instrument that successfully transmitted a complete sentence. To his assistant in another room, Bell conveyed the message: "Mr. Watson, come here, I want you."

Bell's telephone was very simple. It consisted of a metal diaphragm placed in the field of a horseshoe magnet. The diaphragm, vibrating under the impact of sound waves, produced oscillations in the electric current transmitted along the wires. A similar device at the other end of the line turned the electric oscillations into sound.

Russian inventors made several important improvements in the telephone. In 1879 the Russian engineer Mikhalsky made a microphone with powdered carbon, a prototype of the present-day microphone. In this microphone the diaphragm, vibrating under the influence of the sound waves, exerted a pressure on the powdered carbon in proportion to the intensity of the sound. The consequent changes in the density of the powder changed its electrical resistance accordingly.

Another Russian inventor, Golubitsky, in 1880 improved the receiver. His receiver was far more sensitive than Bell's.

These and other inventions extended the range of -telephone communications to distances of up to 350 kilometres. St. Petersburg was soon linked by telephone lo Gatchina and Petergof.

In 1880 a Russian military communications expert G. Ignatyev invented a device that made it possible to use the same wire simultaneously for a telephone conversation and for telegraph communication. Today the method of frequency modulation³ makes it possible to transmit several hundred telephone conversations over the same wire simultaneously.

The telegraph and the telephone were both hailed as the "final" solution to the communications problem. But they were soon followed by an even more wonderful invention, which made possible communication without wires .. .