Sisvel S.p.A.
www.sisvel.com Via Sestriere, 100 10060 None (TO), Italy Phone: +39-011-9904114 Fax: +39-011-9863725 Foro Buonaparte, 51 |
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MAIN CHARACTERISTICS |
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THE DIFFERENCES FROM THE TELETEXT STANDARD |
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CURRENT PROJECTS OF THE TELETEXT DECODERS |
| NEW PROJECTS OF THE TELETEXT DECODERS | |
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THE FASTEXT (FLOF) PROJECT AND ITS DISADVANTAGES |
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THE TOP PROCEDURE (TABLE OF PAGES) |
| THE CTT PROCEDURE (CYCLE TRACE TABLE) |
The CTT (Cycle Trace Table) procedure consists in the construction, by way of the teletext decoder, of a TOP table with the scanning of all the teletext pages present in the cycle. The television set memorizes in a Table of Pages (TOP) the list of all the pages that can be received at that moment, so as to be in a position to know in advance which are the pages actually available. Therefore, when the user selects the successive page with the appropriate function key (normally the green key), the television is in a position to skip the absent pages and to directly acquire the successive page actually transmitted. This simplified version of the TOP procedure can be also activated if the TOP table is transmitted independently from the broadcaster that distributes the service. In such a case the teletext decoder needs a waiting time that varies between 20 to 30 seconds in order to scan all the pages received in a cycle and to construct the TOP table by itself, therefore called Cycle Trace Table. Normally the teletext decoder of television sets compatible with the CTT technology add an additional line in the teletext page, that at least includes the two entries to the red and green function keys of the TOP. The entries are generally characterized by the characters "-" and "+" or "<<" and ">>", the first in red and the second in green relating to the commands "select previous page" and select "successive page".
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