The Picturephone System: The Network

Picturephone service adds a new dimension to telephone communication--that of sight. This face-to-face communication capability will be realized by taking maximum advantage of the existing nationwide telephone network. 1 Although the advantage of more complete communication between people with Picturephone service is readily apparent, the switched Picturephone network will be useful in additional ways, (i) Simple graphic material, such as line drawings will be displayed and, if higher resolution is desired, slowly scanned images will be transmitted. (ii) The network will be used to communicate with a computer. High-speed data will be transmitted between business machines in the megabitper-second range. (Hi) Moreover, Picturephone service will be used to communicate among groups of people in conference rooms or by a 221 222 T H E BELL SYSTEM T E C H N I C A L J O U R N A L , FEBRUARY 1971 number of individual persons at many different locations, (w) It will even be used for surveillance of events at distant locations. Some of these additional uses will be possible at the outset of service; the rest will come later. There will surely be more applications, some yet to be thought of. Important as these additional uses might become, the Picturephone network is expected to be used predominantly for face-to-face communication in much the same way as the telephone network is used predominantly for voice communication. Further, each of the additional uses, while important to a particular segment of the market, requires its own set of system parameters to match the system to the application best.