Interactive Network Inc., which has been providing interactive television service exclusively in the San Francisco and Sacramento areas, will roll out its 20-hour-a-day entertainment service in Chicago in September. The network plans to expand to additional major metropolitan markets in the spring.

The company’s multichannel system enables subscribers at home to play along with TV gameshows on a simultaneous or “real time” basis, with or without cable installation, using a hand-held, wireless, portable control unit.

The basic cost of the interactive programming in Chicago will be $ 299. The complete programming service costs $ 15 per month; for an additional $ 10 per month, subscribers will be able to compete against each other for prizes.

The interactive data for national TV programs will originate in the production studio at Interactive Network’s headquarters in Mountain View, and data transmission for local TV programming will originate from the company’s production facility in Chicago.

Sales of the company’s interactive TV service to Chicago will be built around a 30-minute infomercial and informal pitches at retail stores.

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