Data broadcasting in the USA: low cost delivery alternative and more

摘要

It is pointed out that the unused portion of a television signal's vertical blanking interval (VBI) offers a low-cost alternative transmission system for many point-to-multipoint applications. Using the local broadcast signal as the 'last mile' delivery, television signals can provide a reliable bypass of the local phone system. A high-speed digital data communications system using the VBI of both the national and local public television signals in the US has been undergoing development recently. This development is discussed, as are some of the commercial and educational applications now in use and/or being developed.