초록 ▼

A high security pay television system is provided in which subscribers are provided with a decoder and with periodically changed removable memory modules. The decoder only functions to properly descramble the scrambled broadcast signal when a changeable system-wide code is available in the decoder.

A high security pay television system is provided in which subscribers are provided with a decoder and with periodically changed removable memory modules. The decoder only functions to properly descramble the scrambled broadcast signal when a changeable system-wide code is available in the decoder. The code can either be carried in the memory module, or an internal code unique to the decoder and resident in the decoder can be combined with an external code in the removable memory module, and also unique to that decoder, to generate the common systemwide system code. Program viewership is written on the removable memory module which is returned to a central facility for later subscriber billing.

대표청구항 ▼

In a pay television system, a receiving station signal decoder for a scrambled broadcast signal comprising an internal fixed memory containing a fixed, station-unique internal code; a removable, electrically alterable, removable memory module containing at least one pre-written station-unique, exter

In a pay television system, a receiving station signal decoder for a scrambled broadcast signal comprising an internal fixed memory containing a fixed, station-unique internal code; a removable, electrically alterable, removable memory module containing at least one pre-written station-unique, external code which can be combined with the internal code to generate a systemwide system code, and also a portion onto which program information may be entered; means for generating a descrambling signal complementary to the scrambling signal upon input of a proper numerical sequence; and a microprocessor programmed (1) to read the internal code from the fixed memory and the external code from the portable memory module, (2) to combine the external code with the internal code to generate the systemwide system code, to generate and output to the descrambling signal generating means a numerical signal generated from the system code, (4) to derive a broadcast code from the scrambled broadcast signal, and (5) to write information about programs actually descrambled, as determined from the broadcast code, in the memory module so that use of the decoder can be billed on a usage basis.