background, allowing it to be registered as an input. Since the size of a dot was dependent on pressure (how hard the person was pressing on the glass), the system was somewhat pressure-sensitive as well. Of note, this system was input only and not able to display graphics. In 1983, Bell Labs at Murray Hill published a comprehensive discussion of touch-screen based interfaces, though it makes no mention of multiple fingers. In the same year, the video-based Video Place/Video Desk system of Myron Krueger was influential in development of multi-touch gestures such as pinch-to-zoom, though this system had no touch interaction itself. By 1984, both Bell Labs and Carnegie Mellon University had working multi-touch-screen prototypes – both input and graphics – that could respond interactively in response to multiple finger inputs. The Bell Labs system was based on capacitive coupling of fingers, whereas the CMU system was optical. In 1985, the canonical multitouch pinch-to-zoom gesture was demonstrated, with coordinated graphics, on CMU's system. In October 1985, Steve Jobs signed a non-disclosure agreement to tour CMU's Sensor Frame multi-touch lab. In 1990, Sears et al. published a review of academic research on single and multi-touch touchscreen human–computer interaction of the time, describing single touch gestures such as rotating knobs, swiping the screen to activate a switch (or a U-shaped gesture for a toggle switch), and touchscreen keyboards (including a study that showed that users could type at 25 words per minute for a touchscreen keyboard compared with 58 words per minute for a standard keyboard, with multi-touch hypothesized to improve data entry rate); multi-touch gestures such as selecting a range of a line, connecting objects, and a "tap-click" gesture to select while maintaining location with another finger are also described. In 1991, Pierre Wellner advanced the topic publishing about his multi-touch "Digital Desk", which supported multi-finger and pinching motions. Various companies expanded upon these inventions in the beginning of the twenty-first century. 2000 – present day Between 1999 and 2005, the company Fingerworks developed various multi-touch technologies, including Touchstream keyboards and the iGesture Pad. in the early 2000s Alan Hedge, professor of human factors and ergonomics at Cornell University published several studies about this technology. In 2005, Apple acquired Fingerworks and its multi-touch technology. In 2004, french start-up JazzMutant developed the Lemur Input Device, a music controller that became in 2005 the first commercial product to feature a proprietary transparent multi-touch