FOERFARANDE FOER DEKODNING AV SAENDA FOERVRAENGDA SIGNALER.

摘要

In a pay television system a programme signal is transmitted scrambled to prevent its authorised reception, the scrambled signal being accompanied by authorisation codes, one for each authorised subscriber, a subscription key and a pay-per-view key. At a receiver if the appropriate authorisation code is received the receiver functions in the subscription mode in which mode the subscription key provides for the descrambling of the programme signal. If the appropriate authorisation code is not received indicating that the subscriber is not pre-authorised to receive the programme in an intelligible manner, the receiver is set to function in a pay-per-view mode in which mode, on request, the pay-per-view key provides for the descrambling of the programme signal. If there is a delay receiving the appropriate authorisation code the receiver can be set into the pay-per-view mode for at least the period of the delay so that the scrambled signal is immediately rendered intelligible.