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8-1-3 DATA TRANSMISSION FORMAT
Teletext data is transmitted on VBI TV line. Subject to availability, Lines 6 to 22 and 318 to 335 may be used to carry Teletext
data packets as shown in Fig. 8-1-3.
A Teletext data packet occupies one TV line. Each packet starts with a clock run-in and framing code
sequence for establishing bit and byte synchronization within the decoder. The framing code has a fixed timing relationship
to the line synchronization pulses of the video signal.
Signalling method:
Bit Rate:
Spectrun of data pulse:
Video baseband signal level of element 1:
Video baseband signal level of element 0:
Capacity of the whole data line:
All manuals and user guides at all-guidesbox.com
Fig. 8-1-3
Binary non-return-to-zero (NRZ);
444 x nominal fHC(6.9375 Mbit/s ± 25 ppm)
Skew symmetrical about 0.5 x bit rate, substantially zero by 5MHz
66 ± 6 % of the difference between Black Level and Peak White Level
Black Level ± 2 %0 V
360 bits organized as 45 bytes. In each byte, the bits are numbered 1 to 8
(LSB to MSB), and are normally transmitted LSB first.
Fig. 8-1-4
– 32 –
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