A serious theoretical basis for the implementation of telephoning was developed by a mechanical engineer in Paris called Charles Bursel from 1849-54. In his dissertation in 1854, he explained the operating principle of the telephone but it never made it to prototype.
In 1844 I. Manzetti first began discussing the idea of the 'speaking telegraph' (telephone) but then this idea didn't develop either. In 1864 Manzetti reported that he had invented the 'speaking telegraph' but had yet to patent his device. Despite this, on November 22, 1865 in a Paris newspaper, an article was published about Manzetti's electric phone invention; a device that could play music loudly and transmit spoken vowels with good quality. The spoken language, however, passes quietly and not clearly. The author wrote:
"Manzetti passes a word with the help of a standard telegraph cable (a device simpler than that used for mailings). Now, two merchants of London and Calcutta can discuss their business instantly. Many experiments were undertaken and they were successful enough to establish the possibility of a practical application of this discovery. Music is transmitted very well. As for words, only those with a lot of vowels are heard distinctly."
Earlier, in August 22, 1865, an edition of La Feuille d'Aoste reported:
"Rumor has it that the British technicians (technical experts), to whom Manzetti demonstrated his method of transmitting words by telegraph wires, were preparing to apply the invention in several private telegraph lines in England."
There is no documentary evidence of the 'theft' of the Manzetti invention by Bell as there are no historical records relating to the installation of the speaking telegraph in the UK or elsewhere at that time. In the UK, no demonstrations of any phone occurred until 1877, when A.G. Bell demonstrated one of his early devices to Queen Victoria and others.
There is documentary proof that Bell was the first to invent the telephone (Canada, July 1874). He created a working model in March 1876.
In the U.S.A. in1860 an immigrant of Italian descent called Antonio Meucci demonstrated a device that could transmit sounds through wires. Antonio Meucci's Telektrofon may be considered the 'main' prototype of all modern telephones. Meucci filed his Patent Application in 1871 but fate decreed that the great invention of the telephone would be attributed throughout history to a different scientist.
It is difficult to say whether Bell embraced Manzetti's work but, given all the facts, we can easily assume that his invention of the telephone was not accidental and largely based on the work of Manzetti and Meucci.
In 1861, German physicist and inventor Johann Philipp Reis presented a device that allowed you to transfer musical tones and human speech by wire. He called it the Telephon. The device adequately conveyed tone but the clarity of speech left much to be desired. So the phone was named 'musical'.
In 1869, professor of Kharkiv University Y.I. Morozov developed the transmitter, which was the prototype of the microphone.