Countdown system for conditional access module
US5590202A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 1995 |
| Grant date | Dec 31, 1996 |
| Priority date | — |
| Expiry date | Jan 18, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N21/658
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A digital conditional access module for a subscriber terminal comprises a decryption device including at least one PID register and an associated countdown register. The decryption device is enabled for decrypting received product packets having a PID matching a PID stored in the PID register so long as the associated countdown register is characterized by a non-zero value. Decryption of a product packet results in the countdown register being decremented by a selected factor, the countdown register being prevented from assuming a zero value by setting its contents to a selected value in response to a received conditional access packet containing a PID matching the PID stored in the PID register. The selected value to which the countdown register is set may also be contained within the received conditional access packet.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.