A Tabulating System
Through experimentation, Hollerith discarded perforated paper tape input and pneumatic signal handling. He fixed on a system in which mechanical counting and sorting of cards by detection of a certain punched hole location and electrically driven signals would yield the required statistics from a very large collection of information.
Hollerith left MIT in 1884 to work at the U.S. Patent Office and on September 29 of that year patented his first invention, a "method, system, and apparatus for compiling statistics," otherwise known as the Hollerith Electric Tabulating System. Thirty U.S. patents and many foreign patents on improved systems would follow.