context: The American Broadcasting Company (ABC) (stylized in its logo as abc since 1957) is an American commercial broadcast television network that is owned by the Disney–ABC Television Group, a subsidiary of Disney Media Networks division of The Walt Disney Company. The network is part of the Big Three television networks. The network is headquartered on Columbus Avenue and West 66th Street in Manhattan, with additional major offices and production facilities in New York City, Los Angeles and Burbank, California.
question: The Big Three uses what communication system?