This European Telecommunication Standard (ETS) is the baseline This ETS is the baseline specification for the provision of interaction channel for Cable TV (CATV) networks. It is not intended to specify a return channel solution associated to each broadcast system because the inter-operability of different delivery media to transport the return channel is desirable. The solutions provided in this ETS for interaction channel for CATV networks are a part of a wider set of alternatives to implement interactive services for DVB systems.