Abstract: A switching system for allowing any one conferee on a video conference to assume the role of manually manipulating the video picture that will be seen by all conferees (chair view). In addition, each individual conferee is allowed to determine their own video picture content or to select the chair view. Further, anyone of conferees can assume the role of determining the chair view. In addition, for the video classroom, a chair view video picture is composed such that the picture displays the visual aid with an insert for an instructor and an insert for a student asking a question. Further, the instructor selects by using a button or mouse which student is to be displayed in the student insert, and the video picture automatically displays that student. In another embodiment of the system, the students request permission to ask a question by actuation of a switch on their telephone set, and the names of students asking questions are displayed on a computer display screen.

Abstract: An adaptive clock recovery arrangement for deriving a synchronous clock from an asynchronous, packet stream such as an asynchronous transfer mode (ATM) cell stream. The deviation in the magnitude of information stored in a first-in-first-out memory is continually monitored, and the synchronous clock frequency, referred to as the adaptive line clock frequency, is adjusted in a plurality of modes, under the control of a processor. The adjustment is made in response to a detected increasing condition of the monitored deviation. The adjustments are open-loop adjustments made without continually adjusting the adaptive line clock frequency based on the monitored deviation. Damping is substantially reduced compared with "conventional" PLL arrangements because the open-loop adjustments result in a rapid frequency correction with perfect or nearly perfect deadbeat damping, i.e. without the frequency oscillations that continue after the correct frequency is reached in closed-loop arrangements.

Abstract: A range of data that is included in a data file is represented among the records of the file by a record of a lower limit of the range and a separate, sequential, record of an upper limit of the range. Each searchable representation of a record, such as a table entry, has a pair of flags to identify the record as a range low limit or a range high limit, or neither. When a conventional binary search of the ordered file records is performed and completed and the sought-for datum is not found, the record last examined during the search is checked. If that last record is lower in the order than the sought-for datum and its low range limit flag is set, or if the record is higher in the order than the sought-for datum and its high range limit flag is set, then the sought-for datum is in the file and is a member of the included range.

Abstract: In a cellular mobile telecommunication system, a method and apparatus for controlling the process of locating a mobile unit from the cell sites. When a mobile unit goes beyond the radio range of its associated controlling cell site, that cell site sends a message to nearby cell sites to measure and report the strength of the received signal from that mobile on each of their directional antennas and to report radio channel availability. These reports are returned to the controlling cell site which compares the received signal strength mesurements against stored thresholds. The controlling cell site generates and transmits to the mobile telecommunications switching office (MTSO) a hand-off request message including a list of candidate hand-off cell sites and directional antennas. The MTSO then selects an available channel associated with one of the candidate cell sites and antennas and generates a sequence of messages to hand-off communications control from the controlling cell site to a candidate cell site.