It is also noteworthy that Scottish-born Alexander Graham Bell made many advancements for the deaf. His concern for them involved led him to pursue a method called "Visible Speech" a technique initiated by his father. This system involved teaching deaf students how to position their tongues, mouth, and lips for each phonetic sound. After Graham received a patent on his telephone, he continued his experiments in communication with the photophone--transmission of sound on a beam of light--as well as his experiments in medical research and in techniques of teaching speech to the deaf.
Bell also invented the Graphophone. By using an engraving stylus, controllable speeds, and wax cylinders and disks, the Graphophone presented a practical approach to sound recording. With the money that he earned from this invention, Bell continued his work for the deaf. In May 8, 1893, his thirteen-year-old prodigy, Helen Keller, took part in the ground-breaking ceremonies of the new Volta Bureau building, which is today an international center relating to the oral education of the deaf.
An innovator as well as an inventor, Bell succeeded his father-in-law as President of the National Geographic Society in 1898. While in this office, Bell transformed a small pamphlet sent out by the society into the graphically beautiful magazine that it is today.
Alexander Graham Bell is most famous for having invented the telephone. His famous demonstration of the device ("Mr. Watson, come here, I need you...") happened in 1876.
As with most major inventions, the telephone was not completely invented by one many. Bell's telephone depended on the work of many other people, but it was Bell who made the first practically usable telephone.
Bell also won many other patents for other devices. However, none of his other inventions was nearly as important as the telephone. So I assume that is the invention you are talking about.
Bell, Alexander Graham (1847-1922), an American inventor, is best known for his invention of the telephone. He was granted his basic telephone patent was granted in 1876. Bell was assisted by Thomas A. Watson in his work for development of telephones, and was given a share in Bell's telephone patents as payment for his early work.
Bell’s father, Alexander Melville Bell, taught deaf-mutes to speak and wrote textbooks on correct speech. He invented "Visible Speech," a system of symbols that indicated the position of the throat, tongue, and lips in making sounds, to help guide the deaf in learning to speak. His grandfather also specialized in speech. Alexander Graham Bell also followed in the footstep of his father and grand father to become a teacher of the deaf. He wished to be remembered as such a teacher than as the inventor of the telephone.
Bell along with his associates developed the method of making phonograph records on wax discs. Also he developed an electrical apparatus to locate bullets in the body. Bell perfected an electric probe which was used in surgery for several years before the X ray was discovered.
Alexander Graham Bell is most well for inventing the telephone. He invented the microphone and later the "electrical speech machine" his name for the first telephone.