Teletext decoders

Details Teletext decoders Teletext decoders

1986-10-09

1988-01-12

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358142, H04N 704

Patent

active

047195100

ABSTRACT:
A teletext decoder for full-channel operation includes a "row-found" register in which a flag is put for each data row which is actually present in a selected teletext page that is received and stored in the page memory of the decoder. The decoder further includes control means which on read-out from the page memory allows the utilisation of only those data rows of the stored page for which there is a flag in the "row-found" register. Because teletext pages can contain different numbers of data rows, it is normally necessary to empty the page memory before a selected new page is received and stored since otherwise data rows of a stored old page which are not over-written by corresponding data rows of the new page would be included in the data read out for the new page. The provision of a flag for each received data row of the new page and the action of the control means prevents this happening. It then becomes unnecessary to delay reception of a new page until an old page has been removed from the page memory. Means are also provided for taking account of parity errors in received character data codes.

REFERENCES:
patent: 4394687 (1983-07-01), Hutt et al.
patent: 4593374 (1986-06-01), Gurumurthy
patent: 4620227 (1986-10-01), Levin et al.
patent: 4636858 (1987-01-01), Hague et al.
patent: 4638497 (1987-01-01), Komatsu et al.

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