Full-field teletext system with dynamic addressability
US4600921A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 19, 1983 |
| Grant date | Jul 15, 1986 |
| Priority date | — |
| Expiry date | Oct 19, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/03
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The present invention permits a teletext system operator to adjust subscriber access to service levels individually by adjusting a code at the head end station. A head-end station transmits a tier description page and a tier authorization page. The tier description page divides the data base into a group of tiers each comprising a defined range of pages. The authorization page lists authorization codes for all subscribers, one code per subscriber. Each subscriber station includes a permanent location code. When access is requested by the subscriber, the subscriber station uses the location code to acquire the authorization code transmitted by the head-end station. The authorization code indicates which tiers the subscriber station may decode. To change the service, the system operator may change the authorization codes at the head-end station or change the range definitions for the service level tiers.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.