AT THE recent NBC affiliates convention in New York, the network revealed its new fall promotional campaign - a series of spots featuring the musical jingle, "N-B-see -us." America will gets its first look at the campaign on the Fourth of July. ABC will follow with "We're the one" on July 9 and CBS a few days later with "Turn us on, we'll turn you on."

Of course we will see through all of this, won't we? We will be able to translate the annual rites of promise into the annual dirge of disappointment. Perhaps it's wise to be skeptical about TV, but when the skepticism turns to cynicism and the race to disbelieve becomes in a medium that - for all the abuses, for all the waste, for all the incredibly bumbled attempts at federal regulation of it - may yet be able to keep the brightest promises ever made on behalf of a mere contraption.

Often even the people who work in television lose sight of its prospects and of broadcast traditions that have their glorious side. At the NBC affiliates convention, despite all of the problems and inadequacies that plague TV and discourage viewers, the big issue for the 700 station representatives attending - their apparent overriding concern of the year - was whether NBC would start its Saturday basketball games earlier so they wouldn't slop over into the local stations' early-evening newscasts.

Network executives dutifully swore that the games will, indeed, start earlier next year. This met with a round of applause. But when David Brinkley and John Chancellor hosted an impressive three-way satellite hookup with correspondents in Rome, London and Washington - all of them discussing the future course of world events - many of the station representatives could be seen bolting from the room for a smoke or a drink.

At a party for the affiliates held the night before, however, it was possible to meet some of the long-time NBC executives who not only embody corporate power but also represent TV pioneers who staked out their brave new world as bravely as Jesse Lasky and Adolph Zukor staked out what became known as Hollywood. You can still see glints of roguish entrepreneurism in these men's eyes and occasionally sense a genuine love for television and its still-fantastic possibilities.

NBC Vice Chairman David C. Adams wistfully recalled the first affiliates convention, in 1948. "There were less than a hundred people there," he said, "and I remember seeing a bunch of station managers and network executives shooting craps in the middle of the ballroom. In a way, it was more fun then than now."

Julian Goodman, NBC chairman, was told that the hiring of Fred Silverman as NBC president had made it "the most interesting network" to write about. "We like to think," he said, "that we always have been." In a way, NBC best typifies what can be good about the mere idea of a "network." Of the three TV networks it's the only one whose corporate offices in New York are in the same building that houses active production facilities, so that you can have a real sense of television happening there.

TV programs sometimes seem so pat and plastic that we forget there are true craftsmen at work, not just in so-called creative jobs but on the technical side as well. Twenty-five years ago this month, Leland Hayward's milestone production of "The Ford 50th Anniversary Show" originated from NBC studios still in use. Among the smaller names in the credits for that historic live telecast were technical director Heino Ripp and announcer Don Pardo. Ripp and Pardo are still at work at NBC - performing functions on NBC's "Saturday Night Live" similar to those they filled a quarter-century ago on the "Ford" spectacular.

Outside the business, it isn't easy to find people who say they love television. The medium hasn't developed even a token cult of connoisseurs or aficionados the way theater, film and ballet have. Some of the people who do fancy themselves wise judges of television brag about how little they watch it, though you would never find a cineaste boasting of hardly ever going to the movies or a theater buff taking pride in the rarity of his visits to the theater. Even constant viewers of TV, unlike theater or film fanatics, have a hard time expressing admiration for programs they do not actually like. Television is expected to be a perpetual enjoyment machine. Unfortunately, the commercial sponsorship system encourages this.

In time there will be a videophile subculture: it is evolving now, as members of the baby-boom generation come to realize that television has played the cultural role in their lives that the movies and radio played in their parents' lives - except that the influence of television has been about a jillion times more pervasive and it has paradoxically been largely taken for granted.

And in time, this generation will control television. The prospects are both good and bad. The unsettling aspect is that this generation will have television experience as its primary frame of reference - TV will have been most responsible for shaping the way they look at life and the world and each other. On the other hand, they may bring to the medium the kind of ambitious daring and zest for experimentation that the first babes in videoland - all of them emigres from other media - brought to TV in its fabulous '50s.

Much of that television is still viewable; in fact more and more of it is making its way back onto the air. This week, Channel 26 and some other public television stations will begin rebroadcasting selected episodes of Edward R. Murrow's series "Person to Person." The historical value of these programs is at least two-fold, since they represent the early use of remote locations in television and in addition bring back into focus such figures as John F. Kennedy, Marilyn Monroe, Humphrey Bogart and Fidel Castro.

Many CBS stations - though not, predictably, the Washington affiliate, WDVM - are currently carrying reprises of CBC News religious broadcasts of the past under the umbrella title "Behold Wondrous Things," on Sunday mornings. These broadcasts have included ambitious early live dramas, ballets and musical performances, including a 1956 antiwar drama, "The Hostages," hosted by Will Rogers Jr. On July 9, a 1963 televised gospel concert by Mahalia Jackson will be retrieved from the archives and broadcast again.

Early television may look slow now, or even clumsy, but you can also sense the fact that trailblazers were trying their best to flex the muscles of the new medium, to exploit and explore its possibilities. Video primitivism had one great advantage over today's technically complex TV: The people who made television then had little choice but to be direct. They couldn't disguise an absence of content under a hailstorm of gimmicks and glitzy tricks. There was a purity and a clarity to it that one hopes will be discovered in the new age of television around the corner, when mastery of TV hardware becomes as common as mastery of the typewriter is now.

On the one hand, TV will become an even more utilitarian appliance, beaming out news wire copy, pictures from weather satellites and price comparisons at the Safeway. On the other hand, this may liberate other available channels for those who have the desire and talent to make of television the art form it has yet to become.

TV has always been a populist medium - which is a fact at the heart of some people's hatred for it - but it will become even more so in the years ahead. The creation of television as well as its reception will be in the hands of more and more people, and the medium will be less and less a one-way experience for viewers. With this we will lose something and gain something, and what we will lose is whatever charisma or imposing magic remains in a network's imprimatur or the phrase "Live From New York" or the sparkle still in the eyes of a David Adams as he talks about the good old days when television was considered not only something of a baby but something of a bastard.

I can still remember, for some strange reason, the way our new 14-inch black-and-white RCA console smelled when it arrived in the living room of long, long ago. I can remember the mahogany finish and the dials that soon managed to fall off. And I can remember with sentimental affection the exhilarating sense of expectancy that came from finding this stranger in the house.

Now and then, in the split second between turning on a television set and the moment when an image first appears, I feel a remnant of that odd and incomparable kick. That is part of the reason I love television and part of the reason I will be proven correct in my stubbon belief that it is the greatest machine we bipeds have ever invented for ourselves. It was thrilling to be there at the beginning and it is thrilling now that a new beginning looms just ahead. CAPTION: Illustration, no caption, by Barsotti; Copyright (c) 1978, The New Yorker Magazine Inc.