Telecommunication
The conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849. However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London.
Elisha Gray and Alexander Bell telephone controversy
The theory that Alexander Graham Bell stole the idea of the telephone rests on the similarity between drawings of liquid transmitters in his lab notebook of March 1876 to those of Gray's patent caveat of the previous month. However, there is extensive evidence that Bell had been using liquid transmitters in various experiments for over three years before that time. In 1875, Bell filed a patent application for a primitive fax machine which included drawings of multiple liquid transmitters and the Patent Office granted his application as Patent No. 161739 in April, 1875—ten months before Gray filed his telephone caveat. Experiments by Bell going back to his youth in Scotland show a steady, logical progression towards development of the telephone. Much of the documentation detailing these experiments includes drawings of liquid transmitters remarkably similar to the design which Bell is alleged to have stolen from Gray in 1876.