NEW YORK (AP) — 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 Sunday, 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 subscription TV households.

Broadcast people, those who remember when US 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 recognises this. Cable properties such as USA, SyFy, CNBC and The Weather Channel mean more to NBC Universal's bottom line than staggering NBC, fourth place in the ratings.

And those cable properties — more than the flagship "Peacock" network as NBC is known — 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 country's first radio network in 1926. Its parent company, the Radio Corporation of America, made radios and realised 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. In fact, all three original broadcast networks can be traced back to NBC.

One of its original owners, Westinghouse Electric Co., bought CBS in 1995.

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

RCA's chief David Sarnoff took to the airwaves to introduce that broadcast, and his description of the moment — "the birth of a new art bound to affect all society" — was prescient and maybe even understated. The Nielsen Co. reported that just last year, the average American watched four hours and 49 minutes of television each day.

"He was as much a cheerleader as he was an investor," Podrazik said, "and he was right."

Television's early years had NBC and CBS fighting for dominance, with CBS more often than not gaining the upper hand. NBC settled for innovation, and the work of executive Sylvester (Pat) Weaver is still apparent today. He introduced the concept of multiple ads appearing on shows, instead of programmes that had single sponsors, according to the Museum of Broadcast Communications.

NBC slumped in the late 1970s and early 1980s. Spin-off 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 was not simply the most popular network. It was the best. That seems more distant each year, and not just in time.

NBC's decline has been slow, steady and sad. Their "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 criticising the network for cancelling his expensive drama "Southland" this fall before the season's first episode aired.

Former "Tonight" late night talk show host Jay Leno's move to prime-time, replacing more expensive scripted show at the 11 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 cell phones. NBC is a founding partner in Hulu, an ad-supported web 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.