When 2,800 technicians, writers and producers walked off their jobs at NBC on June 29, they saw immediate signs that the network missed their expertise. The losses ranged from lofty to humorous -- from commentator John Chancellor canceling a prime time special on the Constitution to a Los Angeles weatherman apologetically spinning a globe as a makeshift replacement for the weather map.

But while some workers were celebrating the signs that their absence was noticed, others have been picking up chilling signals that managers and efficiency experts are using this period to determine whether their jobs are becoming obsolete.

The strike by the National Association of Broadcast Employees and Technicians (NABET), which cut NBC's work force by a third, has offered General Electric Co., the network's new owners, a bonanza of information about how to live adequately on less.

"What the strike is helping us to {do} is to use this period as a laboratory for us to find out exactly what we can do and exactly how flexible we can be as we don't have to abide by ... some of the archaic work rules that now apply in the union contract," NBC News President Lawrence Grossman told reporters in Los Angeles last month. "So we're learning, in a practical laboratory way, an awful lot about how we can operate in the future."

As one key executive at NBC elaborated: "We've got 700 people, including management people, handling 3,500 jobs. And no one is pretending it is as good as it was before, but the question must arise here: 'If you can do with 700 as adequately as we're doing now, do you really need all of the 2,800 {who are on strike}?'"

If those are not encouraging words to the NBC employes marching in front of the network's various operations around the country, there is little solace elsewhere in the big network business. Faced with competition, loss of viewers and increases in costs, other networks have laid off workers and taken aim at all sections of their operations.

As Joseph Fuchs, a media analyst with Kidder Peabody & Co. Inc. in New York City put it recently: "Most people have acknowledged that the broadcasting business operated in an unreal world."

For the news divisions, which lose money at all three major networks, the fear is that new owners who are not as well schooled in the ways of television journalism will see news as a "product," like toasters or light bulbss, and not as a calling. As several journalists said recently, this is an unusual strike for GE because the plant has not shut down. The product, or some vestige of it, is still on the airwaves.

However, when network officials and some journalists look at the less-costly news operations of new and smaller networks, they see a flexibility that is often enviable. At Cable News Network, for example, a reporter who has the technical skills can screen his or her own tape and even edit it, said Ed Turner CNN's executive vice president.

"What has happened is that the entertainment networks' union contracts have developed over decades based on operations in Hollywood where you have some odd arrangements -- all of the stuff you see in theatrical productions," said Turner.

"Since we came into existence in 1980, we were able to create a news-gathering organization that is part of the 1980s," he added. "Ours could take into account the new technology which other networks are trying to catch up with, and I don't blame them."

Thus, as corporate owners look at network news and try to see ways to trim costs, correspondents and technicians alike worry that they are applying the mathematics of efficiency to the profession of journalism. When CBS announced its latest personnel cuts, for example, executives made it clear that they had been counting the number of times a correspondent had been on the air and dividing it into his or her salary.

Among journalists, this is viewed as a crude measure of journalistic output since some television correspondents are assigned to beats that traditionally get less attention and require more work per story.

While none of the big network anchors has taken a pay cut yet, correspondents have already begun to see the new corporate methods as they renegotiate their contracts and find the networks less willing to consider them irreplaceable.

Now the technicians, who make up most of the NBC NABET union membership, have begun to feel the accountant's pen. "Essentially, NABET has to come to the party," said one GE official.

The "techs," as they are known in the news business, earn a base pay of about $43,000 at NBC. But because of complex penalty and overtime provisions -- called "golden time" by those in the news business -- the NABET employes earn an average of $64,000. During a campaign year such as 1984, a member of a network crew can earn $100,000 or more, according to network sources.

As one NBC reporter put it: "Many of our people lived on what seemed like an endless supply of overtime dollars."

But as most NABET employes know only too well, Mom and Pop are no longer running the network store. NBC is owned now by General Electric, which has its own ideas about how to deal with union people, and it is clearly not the easy paternalism of the past.

Moreover, if there seemed to be hope of embarrassing GE with such striking placards as "You can't spell greed without G.E." or with Democratic politicians refusing interviews with nonunion NBC crews, CBS has dampened some of those hopes. With negotiations starting at the end of this month for its technicians, CBS sent out a first offer that also signaled that it would be tougher this time at the bargaining table.

As a memo from Michael G. Deleso and the CBS negotiating team of the International Brotherhood of Electrical Workers said on July 17, the NABET proposals "can't compare in its devastations" to CBS' offer to IBEW. The CBS proposal, which takes a swipe at the seniority system, makes it clear that network employes are seeing a twilight of the golden days for cameramen, soundmen, tape editors and others in the technical side of the television business.

NBC executives say the main fight now is over something called "daily hires." At present, NBC cannot hire free-lance crews for one day at a time. It must commit to hiring them for two weeks. The result is that the network keeps regular crews working very long hours and, after a certain time, earning double their normal salaries.

"Our problem is that there is no requirement to create new regular jobs. As they would lay off people, we would deteriorate into a daily hire union. We feel it is a concept based more on favoritism, " said John Krieger, assistant network coordinator for NABET.

The network has also revised its contract so that if NBC buys a new station, for example, the new employes would not automatically be added to NABET's ranks. GE and NBC, which some insiders see as wanting to get into the lucrative television station market, would be able to negotiate a completely new labor contract with employes of any acquisitions.

This preamble to the NBC contract has some union officials worried that it will be expanded in less straightforward ways to slowly erode their membership.

"If they move a news bureau to a different location, like from Atlanta to a suburb of Atlanta, those people would not be represented by NABET anymore," said Krieger. "They want to change the language because they'll be up to something. They'll shuffle around and we would find ourselves wiped out down the line. It would undermine the very existence of the union."

As the strike continues and both sides seem to move further apart, NBC employes see an employer that is willing to give only around the margins, if at all.

"In the days of live television, NABET had a great deal of bargaining power and the networks were incredibly profitable ... and we weren't looking to take a particularly hard position with NABET," said Day Krolich, NBC's vice president for labor relations.

"At this point in time, the industry clearly has undergone profound changes," said Krolich, who listed competition from smaller networks and cable as well as changes in technology. "We don't want to end up being a dinosaur that's left behind in all this."

Although Krolich and others at NBC said that they merely wanted to shave back expenses and not force NABET onto the streets, the sense among some NABET employes is that the strike may be a way for GE to scale back its entire network.

"Our biggest fear is whether there is a point when NBC could just replace us," said one of the 2,800 NABET producers now on strike. "They don't want a huge work force."

The startling new tactic for NABET was that NBC imposed the contract on NABET workers after an impasse in the negotiations. John Clark, vice president of NABET's local unit in New York City, said recently that NBC's move "is something we've really never seen before in this industry."

"They imposed an impasse, then imposed the contract," said Clark. "That kind of strategy really shows the imprint of GE."

NABET officials immediately called a strike even though some NABET members, particularly writers and producers in the union, wanted a chance to vote on the NBC contract. NBC executives have said that technically they could begin hiring replacements for those on strike at any time.

With pressure building within the union and little relief elsewhere, the one hope for union officials is that NBC, and particularly NBC News, will begin to feel their loss. With the Iran-contra hearings finishing, NBC Nightly News suddenly will have a much harder time filling its news slot with good, well-photographed stories.

Because of the need for fewer cameras in the hearing room, the hearings were "pooled," which meant that the other networks crews rotated and passed out the pictures to the competition.

Now, NBC will have to use the makeshift staff of writers and camera crews that is replacing its regular workers.

Crews in foreign bureaus, where NABET does not have jurisdiction, have been called to fill in the gap left by the domestic technicians, writers and producers.

But that still leaves many other openings. At the White House, for example, couriers and secretaries have replaced crews that are among the best in the business. NBC White House correspondents learned last Monday night that their green crews, after six weeks of training, did not know how to change the camera lighting from daylight to dusk.

Said one senior NBC reporter: "We're very worried that GE will say, 'The programs are still going out, the ad money is still coming in, we're doing it with 2,800 people less. Why do we need all these people?'

"The answer in the news division is that we are not doing what we normally do," the reporter said. "The high-gloss pieces are not being done. The extra interviews that add texture are not being done. We're not doing what a grown-up network does.