Interactive videotex belongs to that class of technical systems which are spatially extended and serve to transmit or transport given objects (electrical current, water, passengers, freight, information, etc.) through a network of appropriate channels. Though not a fully independent system since it is normally owned/operated by the telephone agencies and uses their networks for transmission, interactive videotex is more than just another service offered within an already existing technical system 1 . The existence of technical and social components which are specific to videotex make it meaningful to consider it as a large (socio-) technical system and to study its development. Interactive videotex is based on a special set of (linked) computers serving as data banks, it needs special terminal equipment (though one alternative is the TV screen connected to the telephone plus decoder), and there are special service providers distinct from the national PTT agency.