NEW YORK — Eight decades after pioneering the concept of broadcasting, NBC is on the verge of a startling move that illustrates broadcast television's decline.

Cable TV operator Comcast Corp. is expected to buy a controlling stake in NBC Universal, perhaps as early as this week, bringing the network of Johnny Carson, Jerry Seinfeld, Bob Hope, Milton Berle and Tom Brokaw under the corporate control of the company that owns the Golf Channel and E! Entertainment Television.

"This is highly symbolic," said Tim Brooks, who had worked at NBC for 20 years and now writes books on television history.

Starting today, Vivendi SA has an option to sell its 20 percent stake in NBC Universal. Majority owner General Electric Co. is expected to buy it and then sell a 51 percent stake of the entire NBC Universal unit to Comcast, which serves about a quarter of the nation's cable TV households.

Broadcast people, the folks who remember when television was ABC, CBS, NBC and little else, used to look down upon cable.

The idea of broadcast TV was implied in the name; the networks tried to reach the broadest possible audience. For cable, it's important to do something specific and do it well, and the audience doesn't need to be as large.

NBC Universal Chief Executive Jeff Zucker recognizes this. Cable properties such as USA, SyFy, CNBC and The Weather Channel mean more to NBC Universal's bottom line than staggering NBC, which is in fourth place in the ratings.

And those cable properties — more than the flagship "Peacock" network — were the draw for Comcast. By owning more content, Comcast further hedges its bets as mainly a distributor of shows in case viewers ditch their cable TV subscriptions and migrate to the Internet, mobile devices or a platform that has yet to emerge. The company could charge for the shows or sell ads wherever the viewers are.

In a sense, NBC would become a pioneer again, as it seeks to stay relevant amid intensifying audience fragmentation.

NBC was established as the nation's first radio network in 1926. Its parent company, the Radio Corporation of America, made radios and realized the best way to get people to buy the product was to make sure there were interesting things to listen to.

"Without NBC, there wouldn't be broadcasting as we know it," said Walter J. Podrazik, a consulting curator at the Museum of Broadcast Communications.

NBC was the leading radio network, so powerful in those days it had two networks: NBC-Red and NBC-Blue. It was forced by the Federal Communications Commission in the early 1940s to divest itself of one network. NBC-Blue eventually became ABC.

Some of NBC's radio profits were funneled into researching the new television technology. NBC began television broadcasts in 1939 by covering the opening of the New York World's Fair.

In 1947 came the first NBC program that's still around today — Sunday morning's "Meet the Press." But 1948's "Texaco Star Theater" with Milton Berle was television's first big hit. Many people bought their first TVs to see a comic who'd mine for laughs each week by wearing a dress.

NBC News expanded in the 1960s, and the evening news report with David Brinkley and Chet Huntley made "Good night, David" and "Good night, Chet" simple catch phrases. News is a strong suit for NBC today, with Brokaw retiring at the top and Brian Williams continuing the legacy. The "Today" show has been No. 1 in the ratings for 726 consecutive weeks.

There's been no such consistency in prime time through the years, however.

NBC slumped in the late 1970s and early 1980s, when the "Supertrain" series became a shorthand for a comically inept idea. Spinoff ABC surpassed NBC in ratings. One man changed all that: Bill Cosby's sitcom dominated television in the mid-1980s, as millions of Americans checked in each week on the Huxtable family.

In the 1990s, NBC's promotion team dubbed Thursdays as a "must-see" night of television. The slogan stuck because it was true. The network's run of memorable series including "Cheers," "Seinfeld," "ER," "Frasier," "Friends" and "The West Wing" represented a golden age.

NBC's decline has been slow and sad. Its "must-see" series all ran their course, replaced by nothing comparable. Each of their rivals minted influential, highly popular reality series — Fox's "American Idol," ABC's "Who Wants to Be a Millionaire" and CBS' "Survivor" — yet the best NBC could do were the moderately successful "The Apprentice" and gross-out show "Fear Factor."

Worse yet is Hollywood's impression that NBC now is more interested in saving money than in producing memorable television.

Famed producer John Wells said as much in criticizing the network for canceling his expensive drama "Southland" this fall before the season's first episode aired. Jay Leno's move to prime-time, replacing more expensive scripted show at the 10 p.m. slot, reduced NBC's audience and influence even more.

NBC is turning, some of its fans fear, into something comparable to a cable network in ambition and reach.

Yet Comcast may give the network hope as audiences turn to video on the Internet and mobile phones. NBC is a founding partner in Hulu, an ad-supported site that lets viewers watch shows for free. NBC's combination with Comcast could let the network take advantage of the cable operator's efforts to reach additional platforms.

The fact that Zucker would likely stay at the helm, reporting to Comcast executives, suggests that the cable operator won't be making major changes overnight.

A Comcast takeover is largely symbolic now, though practical reality ultimately may overshadow that as NBC and other broadcasters face declining audiences.

"The question," Brooks said, "is what will they do with it?"