Commercial use of the VBI [vertical blanking interval]

Each line within the VBI provides a theoretical 16 kilobits per second of data capacity (50 [transmissions per second]*40 [usable bytes]*8 [bits]). When bids for commercial licenses were invited in mid 1992 the problem was how to exploit the three lines of capacity (48 kilobits per second) that were offered to the best commercial advantage. The approach chosen was to offer a combination of pseudo-page and packet 31 services (World System Teletext sections 20 and 21) using two of the three lines on offer and to leave the third in reserve for resale to a single suboperator