H - Electricity – 04 – N
Patent
H - Electricity
04
N
350/34
H04N 7/04 (2006.01) H04N 3/16 (2006.01) H04N 5/68 (2006.01)
Patent
CA 1199399
ABSTRACT OF THE DISCLOSURE The apparatus for displaying graphic messages transmitted by videotext systems on a television receiver screen which is comprised of a data separator, a page memory, a character generator, a management circuit, a service definition keyboard connected to the management circuit, internal synchronization generation circuitry, a circuit to separate the external synchronization of the broadcasting network, and circuitry for controlling interlaced and noninterlaced sweeping. It also is comprised of phase locking apparatus, first switching apparatus to connect the phase locking apparatus to the internal synchronization generation circuitry, and switching apparatus to selectively switch the interlaced and non-interlaced sweep control circuitry. A working state indicator output is provided in the data demodulator in addition to the data output. A first byte type identification circuit is provided in the management circuit to recognize the type of synchronization in the bytes of the first row of each page. First logic circuitry is arranged between the first identification circuit and the output of the working state indicator of the data demodulator, on one hand, and the first and second switching circuit, on the other hand, to control the first and second switching circuit in relation to the state of the first identification circuit and the state output of the demodulator. The management circuit may also be comprised of a second identification circuit for subtitle bytes among the bytes of the first row of each page, whose output is connected by third logic circuitry to control the switching of the normal video-graphic video switch during insertion lines.
406121
Etat Francais Represente Par Le Ministre Des P.t.t. (centre National D'etudes
Shapiro Cohen
Telediffusion de France
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