Through 1967, CBS had a pair of announcers call all the games of one team for an entire season, with "split" feeds, one going to the visiting team's home region, the other to the home team's region (other than stations in or within 75 miles of the city the game was being played in).
For example, in 1963, a game between the Washington Redskins and New York Giants in New York (Yankee Stadium), CBS viewers in Washington and the rest of the Redskins' "network" (which back then extended through the Southeast) would hear Jim Gibbons and Eddie Gallagher, while those in upstate New York and New England (network flagship WCBS-2 in New York was blacked-out and didn't carry the game) heard Chris Schenkel and a young Pat Summerall.
Oddly enough, in 1964, CBS abolished "split feeds" and had the visiting team announcers do one half and the home team announcers the other half. They went back to their "split feed" system for the next three seasons.
After 1967, CBS ended their "split feeds" and had just one team of announcers doing each game, who would be heard on all stations carrying that game. The announcing teams also were ranked in experience and ability, so the "top" tandem would get the "biggest" regional game each week, the "second" tandem the next-most-important regional game, etc. NBC was alerady using this system for the American Football League.
