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 filters; especially when you consider that we are dealing with RF signal levels typically in excess of one millivolt in a cable environment, so that a lot of gain is simply not required.

We have had such a system going at Sanders several years ago; at the time we generated a demonstration video tape in cooperation with Warner Communications people and facilities in the Boston area. This tape allows us to demonstrate a Cooperate CATV Game Channel transmission of a number of interactive sports games. The most interesting of these games was a Hockey Game in which both a colorful playing field was transmitted plus four randomly moving hockey player symbols, two goalies and two forwards. Our receiving equipment has the capability for recognizing the presence of these player symbols in real time; after that is done it is easy to introduce them into the logic circuitry of our Game Box and treat them just as though we had generated them in logic ourselves; as a result, these precanned player symbols can stop or reverse the ball motion and effectively interact with two manually controlled, locally generated player symbol of the ordinary variety. It is amazing how often the randomly moving, prerecorded player-symbols happen to be in the right place at the right time. When you watch or play a game like that you get the impression of playing with a couple of partners that at times play a terrific game and at other times can't seem to do anything right. What could be more natural than that?!

Looking ahead to future solutions for interactive games of this type, the use of Vertical Interval located digital data for game control comes to mind immediately. This comment applies both to my Category 2. and 3. Cable Games. The latter, you may remember, involve microprocessor aided Cable TV Games. As I indicated earlier, transmitting data to the computer's RAM or ROM storage during Vertical Interval is a natural technique.

In this connection a technique for transmitting digital data via a standard, unmodified TV set might be of interest to some of you. At Sanders we call this method a Digital Video Modem (Ref. 2) because it involves the transmission of data bitstreams at rates which can be many times that of vertical field rate, and which appears as a small, visible display in the corner of the TV picture. It is then photo- optically coupled into a digital decoder, much as you would use a telephone line modem for the recovery of transmitted digital data. This modem can be combined with the sync extraction and regeneration techniques I described earlier to provide data for microprocessor aided TV Games on one hand; or for the Category 4. games. Let me use the "What's My Line?" example again to illustrate this application of Digital Video Modems. In this situation, the home viewer might get privileged information, such as a multiple choice clues, as to the identify of the Mystery Guest. By using this transmitted digital data we can give the home viewer the satisfaction of beating the expert studio participants at their own game.

Horoscope, Ramtek's coin-operated, microprocessor-controlled system, is capable of providing five different charts, based on personal data input.