Abstract: In a multilocation video conference system, contention for the video to be transmitted to the locations is resolved by employing so-called talker and graphics contention resolution processes. Both the talker and graphics contention processes may be overridden by manual selection of the video to be viewed at each location. In the talker contention process, the video to be transmitted is not switched until one and only one talker location is detected during a predetermined talker timing interval. In the graphics contention process, all requests for graphics transmission are rejected until one and only one graphics transmission request is detected during a predetermined graphics request timing interval. Once transmission of graphics has been assigned to a location, all other locations in the conference are transmitted the graphics video information until the location displaying graphics releases from the graphics transmission mode or there is a manual override.

Abstract: In a multilocation video conference system, conference locations are dynamically added to or deleted from an ongoing conference without disrupting it. This is realized by controllably enabling or disabling communications ports assigned to the conference locations in a Multilocation Conference Terminal (MLCT). Both audio information and control channel information transmitted from a conference location assigned to a port are monitored to determine if the audio information is satisfactory and if the control channel communication is "good". If the audio information is unsatisfactory, it is muted and selection of the video from that location as a one-and-only-one talker is inhibited. If the control channel communication is not good the video signal from the conference location is excluded from the conference.

Abstract: In a Multilocation Conference Terminal (MLCT), disruptions in the video being viewed which are caused by switching from one conference location to another are minimized by delaying switching of the video signal until a so-called get ready control signal is received from the conference location to be viewed. The conference location transmits the get ready control signal a predetermined interval prior to transmitting a so-called fast video picture update in response to a request from a Multilocation Conference Terminal (MLCT). Additional possible disruptions in the video are eliminated by minimizing the number of fast video picture updates that are used to serve a multiplicity of requests from other conference locations. When multiple MLCTs are employed in a conference, the MLCTs communicate to each other the video select modes of all the conference locations in the conference, i.e., a manual select mode or an automatic select mode.