TVEI

During each broadcast the lecturer at the TVEI centre in Gwynedd would use a VC7000 videophone to contact the VC7000 in Senate House and a computer terminal connected to the LVR via the Internet. The terminal was used to select previously recorded pictures from the LVR and switch the feed to the satellite uplink in Plymouth between the VC7000 and the LVR. Using a local satellite receiver the lecturer could see the signal being broadcast and switch it between himself and the LVR with the terminal.

A few days before each session the TVEI centre would send the pictures for the next broadcast to Senate House via the Internet where they would be reconstructed and saved on the LVR. There were problems transferring pictures using this method, each picture took several minutes to transfer and the quality of the reconstructed image was never quite as good as the original. For the final broadcasts a diskette was sent from Wales and an Amiga computer used to record the images on the LVR.

Initially two links to London were used, an ISDN line for the VC7000 and a normal analogue phone line with a modem for controlling the LVR and image selection. Unfortunately since the modem connection went via the UCL dial up service which had an inactivity timer the connection would be closed after approximately six minutes of non use. This made sense for normal users but caused problems for the TVEI broadcasts since there would quite often be pauses longer than this between commands being sent to the LVR. The problem was solved by using the data ports on the VC7000 which allowed 9600bps data from the terminal controlling the LVR to be transmitted over the ISDN line to the LIVE-NET computer. The bandwidth was only used when data was being transmitted.

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