>The data is transmitted during the vertical retrace interval of one of the
>TV channels. Your modem will be equipped to handle the appropriate frequency
>for your cable system or satellite or whatever -- it can vary from one system
>to another.
Close... For the standard cable distributed signal it's a simple
FSK modulated carrier at some freqency on the cable. For example,
TCI in Portland OR carries it at 73.0 MHz. I suspect that most
systems carry it near that frequency since it's in the 4 MHz wide
hole that exists between channels 4 and 5. Demodulating this signal
is pretty easy given some of the new RF front end chips that are
available.
>The output of the modem is a 9600 baud stream of partially unintelligable
>stuff. Some if it is simply encoded, and some of it is encrypted. The
>encoded stuff contains the basic information service which X*PRESS offers
>for the cost of the modem only -- there is no monthly charge beyond what
>you're already paying for cable. The encrypted stuff is for premium services
>which X*PRESS offers for a monthly charge, and you need additional software
>in order to get the premium service.
The most important piece needed to get the premium service is a $100
"InfoCipher" decoder module made by GI and only available directly from
X*PRESS. Then for a monthly fee they'll keep it activated.
Regards,
-Tom Kloos, WS7S, Sequent Computer Systems, Inc., Beaverton, OR tk@sequent.com