When the case of American Broadcasting Companies v. Aereo comes before the Supreme Court in April, it will feature two American archetypes in a battle that could upend the television industry.

In one corner will be broadcast networks like ABC, NBC and CBS, powerful companies that have been fixtures in American living rooms for decades, and the conduit for collective national experiences like presidential elections, walks on the moon and the Super Bowl.

In the other corner is Chet Kanojia, a 43-year-old immigrant from India, who as an outsider saw a system that most took for granted and who knew he could build a better mousetrap, or at least a different one. Aereo, Mr. Kanojia’s two-year-old company, has figured out how to grab over-the-air television signals and stream them to subscribers on the Internet. It is an invention that could topple titans.

The titans know it. Intent on maintaining a system that provides billions in revenue annually, the networks have been fighting Aereo in court almost since its inception, claiming the service was stealing their content. This month, the Supreme Court agreed to hear the case.