1. Sign Language evolved worldwide over centuries in a natural fashion, climaxing with the work of Laurent Clerc and Thomas Gallaudet in the United States of America.
2. Hearing Aids also date back hundreds of years, beginning with ear trumpets and ear tubes and culminating (in the 19th and 20th centuries) with carbon transmitters, vacuum tubes, and transistors - all of which amplified sounds.
3. The TTY (or TDD), developed by Robert Weitbrecht in the 1960s, was the first telecommunication device that allowed people who were deaf to communicate with each other (and with the hearing world) over public telephone lines. It become indispensable to millions.
4. A Cochlear Implant is a prosthetic replacement for the inner ear, surgically grafted onto the skull behind the ear and electronically stimulating the hearing nerve with small wires touching the cochlea (a spiral tube).
