ystem will be able to absorb new features and specifications without affecting people using previous-generation devices. Customized software will play a key role in Oxygen's day-to-day use. An accountant, for example, would use one type of software, whereas a doctor would use another kind of programming package. A user could find himself or herself using several different types of Oxygen software sets: at work, at home, and at play. An intelligent network, dubbed Network21 (N21), lies at the heart of Project Oxygen's communications infrastructure. The network will link an array of stationary and mobile devices. Besides providing communications links across cities, nations, and continents, N21 will support multiple commu- nication protocols to provide low-power point-to-point, building-wide, and campus-wide communication. 2.6.3 User Technologies Project Oxygen's user technologies will mark a radical departure from today's world of desktop PCs, laptop computers, and PDAs. By allowing users to seam- lessly transition between stationary and mobile devices-without the need for time-consuming data syncing-Oxygen aims to make computing and commu- nications almost effortless. NUTS AND BITS-TELECOM HARDWARE, SOFTWARE, AND MORE Because mobility is key to the Project Oxygen philosophy, handheld devices will be one of the system's most important-and interesting- technologies. The basic Oxygen mobile device is the Handy 21 (H21). This small, handheld unit will combine the features of mobile phones, pagers, portable computers, radios, TVs, and remote controls. Oxygen's developers envision a pocket-sized device that will incorporate a microphone, speaker, video screen, and camera. A global positioning system (GPS) module, which would allow the Oxygen system to pinpoint a user's exact location, will also be included. Although H21s will serve as all-purpose, go-anywhere personal computing /communication devices, Project Oxygen researchers also want to bring homes and workplaces into the pervasive computing loop. Enviro21 (E21) de