The ideal session would have all participating sites able to see and hear each other. In practice it was not always possible or desirable to connect all sites together. Since there were only four video trunk channels going to each site a maximum of five sites could participate in a fully interconnected session. There were further limits to how sessions could be set up due to the need to run sessions in parallel and the availability of equipment at each site.
Three main types were run on LIVE-NET, lectures, fully connected seminars/meetings and multiplexed seminar meetings.
When the system is configured for a lecture the signal from the main, or transmitting site, is sent to the receiving sites whilst all the receiving sites are sent to the transmitting site. This means the transmitting site can see and hear all the receiving sites whilst the receiving sites can only see the transmitting site and not each other. This configuration allows the lecturer to see and hear remote students and lets the students ask questions, however students at two different remote sites can not see or hear each other. This configuration proved to be quite successful in practice. Its only drawback being that the lecturer had to repeat questions so that students at all the remote sites could hear what was asked.
A seminar or meeting requires a much greater degree of participation between sites than a lecture. Because of this all the sites are connected to each other. This was the most expensive type of session in terms of resources used, a five site session would use all the trunk channels to the remote sites and need four video monitors at each site.
As a compromise quad splits were used to combine the video from up to four sites into a single picture which would be sent to each site. Two quad splits could be used which allowed up to eight sessions to participate in a meeting. Normally a control program would be used to select which picture would appear full screen at each site. As discussed previously there were problems with this.
In practice the set up of sessions tended to be more complicated than indicated. Some sessions had to be recorded and modifications made to the connections to allow for situations when not all the trunk channels to a site would be available either due other sessions running in parallel or trunk channels being taken out of service.
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