Access system and method for providing interactive access to an information source through a television distribution system

An interactive access system for accessing an information source through a television distribution system, which comprises: a television distribution network comprising a network headend, a plurality of terminals, a plurality of upstream channels, and a plurality of downstream channels; each downstream channel being used to carry a TV transmission including a plurality of sequentially transmitted picture fields, each transmitted picture field comprising a picture interval corresponding to the transmission of a pixeled picture data, and a blank interval corresponding to the transmission of a non-pixeled picture data; each upstream channel being used to carry data transmission to the network headend; headend distribution equipment interfacing with the network headend of the television transmission network for distributing television transmission on separate downstream channel in the television distribution network; and a plurality of terminals each interfacing with one terminal of the television transmission fo