Bell\ˈbel\ , Alexander Graham(1847–1922), American inventor. Bell began his career in the fields of speech and acoustics. Training teachers of the deaf, he and his father developed “visible speech,” a system of symbolic representations of the physical process of speech. His investigations into the application of electricity to the production and analysis of sound resulted in the invention of a multiplexing telegraph system. Further experimentation in telegraphy led to work on a method of electrically transmitting actual voice sounds, and in 1876 his work culminated in the invention of the telephone. Later inventions included a telephonic device using the modulation of a light beam, an audiometer, an improved phonograph, and an electrical induction device for the detection of metallic objects in the body. Throughout his life he remained deeply interested in the teaching of speech to the deaf.