Communication of individual messages to subscribers in a subscription television system
US4829569A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 8, 1986 |
| Grant date | May 9, 1989 |
| Priority date | — |
| Expiry date | Jul 8, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/163
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A subscription television system in which individual decoders are enabled to receive individually addressed messages is disclosed. The composite signal, including video and teletext, also comprises addressed packets, which are detected by decoders and which indicate that a message addressed to a particular subscriber is forthcoming, and system control data. The decoder detects an addressed packet addressed to itself, whereby it is enabled to select the appropriate teletext message and to display the same. In a preferred embodiment, both address packets and teletext are encrypted. The addressed packet is decrypted using a decoder-specific code and a system key transmitted as part of the system control data, while the teletext packet is decrypted using the system key, but cannot be received until the addressed packet has been decrypted. Therefore, redundant levels of security are provided to the system. Messages for display to the user can be selected in response to user initiated commands, in response to decoder initiation, or in response to the transmitter. In each case, the bulk of the data to be displayed is repetitively transmitted by the transmitter and is adapted to the partic…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.