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Both BMI and DBC use the vertical blanking interval (VBI) of a television
signal to transmit their data. Each line transmits 9600 baud and there are
nineteen lines which have been deregulated for commercial use. Some are in use
for such applications as impaired hearing text.
DBC historically has used two lines and BMI four. These lines are leased from
the cable networks and are passed by the cable system for an additional fee.
The Signal box was designed to read two VBI lines; the BMI box is essentially
a double box which reads 4 lines.
All this made economic sense before the internet and before the threat of
digital television, which scrambles the VBI. The FM sideband technology which
DBC uses also made sense at one time. None of these technologies make economic
sense anymore in the face of the internet, which essentially carries the
signal for nothing. This is evident in the pricing disparity between internet
feeds and feeds using other technology.
Rail all you want against DBC and BMI and their bandwidth limitations, but
economic realities dictate that no new investment will be made in these
technologies that are at a cost disadvantage.
It will soon be a choice of internet or satellite, with telco for those who
can afford it. Learn to accept this reality in the same way you accept a bad
trade.
jfb
shaven heads trading
new york city
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