A digital satellite television system has a plurality of set-top-boxes associated with a plurality of end users' television receivers, a modem and a decoder housed in each STB, a Subscriber Authorization System (SAS) incorporating or having associated therewith a plurality of communication servers, means included in the SAS for generating Electronic Managements Messages (EMM), a back channel interconnecting each of the STBs individually with the SAS, means included in the SAS and each STB so that the necessary information required to inject a relevant EMM into the system is supplied directly to the relevant communication server included in or associated with the SAS to authorize the release of the said EMM and/or means to connect the modem to the back channel and means whereby an EMM is transmissible to the decoder directly from a relevant communication server included in or associated with the SAS. Further important features are also disclosed.