Otis is the largest global elevator and escalator supplier by revenue with around 18% global market share. In 1854 Otis' founder and namesake Elisha Graves Otis, invented a safety mechanism that prevented elevators from falling if the hoisting cable failed. The company's product and service lifecycle begins with installations of elevator units in new buildings, later selling maintenance services on the units, and eventually replacement of the units after the average 15- to 20-year useful life of an elevator. As the largest global OEM, Otis has amassed an installed base under service that exceeds 2 million elevators. Its business model is similar to that of its closest competitors Kone, Schindler, and TK Elevator.