Softel have developed the SE3043/A/B Teletext drop
and insert units to extract Teletext data from a video
signal, output it on a communications link as a single
serial datastream, and to re-insert the data as Teletext
at the other end of the link.
The
units were originally designed for use on 34Mbit Video
Codec links where the Teletext is carried separately
from the video using 384kbps auxiliary data channel.
The
drop and insert units can also be used in the same
way on digital compression links (such as the NTL
2000 system) and in networks where the teletext generator
is remote from the required point of insertion. Where
there is no video carrier but the need to carry a
full VBI teletext service between two points, the
units may be used at either end of a PTT kilostream
link.
Each
VBI line carried (even & odd) requires a bandwidth
of approximately 20kbps clock and data synchronous
link.
The
insert unit can optionally also insert CCIR and UK
ITS test signals in addition to the Teletext data.
There is no requirement for teletext data to be synchronous
with the video. The SE3043A drop and SE3043B insert
units are both 1U 19" rack mounting, with a choice
of AC or DC power input.
SE3043A Teletext Drop Unit