Regarding TV over IP, only one TV program (the one which the subscriber has selected) is transmitted at any given moment on the subscriber’s line, the selection being performed at the DSLAM level. The fact that only the program selected by the user is transmitted is permitted by the bi-directional feature of the ADSL link, and allows subscription to pay TV and access to ondemand programs without requiring a conditional access system or encryption, since it is possible to check that the user has the required rights to access this program before delivering it. Some pay TV service providers nevertheless require that the IPTV terminal be equipped with a conditional access system to subscribe to it.