There are two main forms of interval timers. The earlier was devised by Matthaus Hipp, Charles Wheatstone and others for measuring small intervals of time. A clockwork mechanism, controlled by a reed, is started and stopped electrically to measure a particular interval. Bashforth's chronograph of 1865 was used to measure the time of flight of projectiles; modern versions are electronically operated. The other form is a clockwork mechanism which, after a set period of time, sounds a bell or buzzer. It is popular for kitchen operations, telephone calls, car parking and so on. These timers may be incorporated in other equipment, e.g. In an electric oven for starting and stopping a period of cooking, and are also much used in industry for timing processes automatically.