"CBS" really stands for the Clutter Broadcasting System.Clutter is what results when you overload the airwaves with promotional announcements for your own shows. Added to all the other commercials on the air promos contribute to an ecological slur not unlike billboards on a highway.

Soon billboards are all you can see.

Once CBS was not only No. 1 in the ratings but the self-styled "Tiffany's" of broadcasting: even during its rube-tube. "Green Acres" era, the network maintained a look of decorum and cirility. it behaved, to use an outmoded term, like a gentleman. Now, it has gone the route of the leader, ABC; it bombards viewers with nearly incessant and consistently raucous audio-visual importunings.

Like this screamer for a rerun of the theatrical feature "Once Is Not Enough": "The world of jetsetters, where anything goes - starting with innocence!"

On Sunday, in the four hours of prime time alone, CBS subjected viewers to a total of seven minutes and 50 seconds' worth of promotional material, either through slam-bang spots or audio plugs performed over the closing theme music of programs. There were four separate mentions of "It's the Great Pumpkin, Charlie Brown," four separate mentions of an upcoming "M*A*S*H" and four of "WKRP in Cincinnati."

Prime time had barely begun - it was 21 minutes into "60 Minutes." when the promotional barrage began with an ad for "All in the Family." "Alice," "Kaz" and "Dallas," all within one 30-second spot. CBS would not allow an advertiser to pitch four separate products within one 30-second spot. Nor is it likely a single commercial would be repeated four times o none network in one evening.

In other words, promos are more irriting than commercials, and CBS has hyped up its on-air promo department this year to make the promos punchier, harsher and more abrasive. All the networks devote about the same amount of time to them (though NBC voluntarily reduced its promo allotment in prime time slightly this year), but the stridency and relentlessness of the CBS promo operation now makes it the most promomantacal network on the air.

"It does not look like clutter to us," declares Gene F. Jankowski, president of the CBS Broadcast Group and, with CBS Entertainment president Robert A. Daly, the man responsible for the big promo push this year. "I guess it's all relative," says Jankowski, declining to state how much more money CBS is spending for on-air promotions this year than it did last year.

"What we have tried to do is make promotional announcements more meaningful, to market our product the way advertisers market theirs," Jankowski says. In other words, promos are no longer, by any stretch, an information service for viewers - "what's on tonight." Instead they are a calculated assault on the audience's vulnerability insofar as impulse viewing is concerned.

If Jankowski doesn't think the promos are an affliction on viewers and a self-blot on the copybook of CBS, some insiders at the network do. They decry such practices as "hysteria," and can't believe that what they're seeing on the air is coming from CBS and not ABC, which long ago established the industry norm for obnoxious, but apparently effective promo ads.

"I'm flattered you think they're hard-hitting," says CBS vice president Steve Sohmer of the on-air promos he supervises from his Hollywood office. "We think we're doing a helluva better job on these." Sohmer hails the spots as "much more lively" and says "they jump off the box at you."

Among the network's brainstorms this year is a re-allocation of so-called "availabilities," or time slots reserved for promos. CBS, with a certain decency, used to save them for station breaks or until the end of a half-hour program. Now they pop up in the middle of shows, clustered with commercials, just like on ABC - the network Sohmer acknowledges as the inspiration for this change.

For over a decade networks have been routinely fading the closing-theme music of a program under an announcer, who recites what's coming on next so as to keep viewers glued to that network. The practice got entirely out of control when networks started squeezing in as many program mentions in that tiny (usually 30- of 40-second) space as they could. But it took the public-be-damned enterprise of CBS to make these promos even more intrusive by using sound effects, laugh tracks and soundtrack excerpts from the shows being plugged.

Sohmer is proud of this achievement.

"What we do is produce our audio promos like they were radio commercials," Sohmer says. "This new approach makes them far more conspicuous. It's easier to tune out the audio promos of the other networks than it is ours."

When a local station isn't carrying a certain network show, it can replace the network's audio promo with an audio promo of its own. Inevitably, as on CBS affiliates WMAR in Baltimore and WDVM in Washington, this is done with raggedy sloppines, so that you hear the beginning of the network's promo and then suddenly the local station's kicks in.

This sort of theing and the profusion of promos in general is turning the airwaves - which belong to the public by government rule - into a slum. When CBS, the haughtiest and most self-important of all the networks, looks and sounds like a junk shop, this can be taken as an indication of how cluttered and frenzied all of television has become.

The FCC has no rules or regulations about promos. The National Association of Broadcasters (NAB) has a complicated mess of regulations about how much "nonprogram material" is permissible during various hours of the day on those stations that belong to this voluntary, hardly all-inclusive group. But advertisers, who see their own commercials drowning in a sea of clutter, think the rules should be tougher, and the NAB is now lackadaisically rewriting them.

Its first proposal of new rules, however, did not meet with industry hoorays. Advertising Age reported that the new system, yet to be finalized, "actually increases allowable nonprogram material from 9 1/2 to 10 minutes" per hour in prime time. Ad Age commented, "Under the most generous interpretation, we see nothing to celebrate," and warned, "An industry which wants Congress to believe the time has come for deregulation must start demonstrating the capacity to discipline itselr."

Sohmer insists that the CBS promos are not as wild or reckless as those of the other networks. "There are many, many specific things that ABC and NBC do in promos that we at CBS, just frankly, are not allowed to do," he says. These include, he claims, showing "any kind of violence" in promos or using double-entendre.

But Donn O'Brien, head of the network's standards and practices department, which has domain over promos as well as ads and programs, says, "Steve is continually hitting me on the head for keeping us where we are with the promos - he'll say, 'ABC does this,' and 'NBC does that,' so why can't he do it."

Sohmer, on the other coast, complains that Standards and Practices "jumps right on top of us if we go six or seven seconds over in our allotted promo time. It just makes me crazy." If the promo time exceeds the NAB limits, a promo is pulled and a public service ad aired in its place. The clutter factor is not affected, however.

Tastefulness lies in the eye of the beholder. The CBS promo campaign for its showing of the movie "Network" was not lurid or violent, but it was hysterical and sensationalistic.Lightning, or an animated facsimile, struck repeatedly on the air, accompanied by booming thunder. In audio spots one heard the thunder-claps and and announcer literally bellowing "Network! Network! Network!!!"

For all that, the picture bombed when it finally was shown. By then, people were probably sick to death of it.

The alleged prohibition against "double-entendre in audio copy" apparently has its limits, too. It did not prevent CBS from having the sexy regular on "WKRP" preface a commercial break by coyly panting. "This is Jennifer, reminding you not to touch that dial - or anything else." A scene used as a "teaser" at the opening of a film called, "Are You in the House Alone?" featured a rapist snarling to a panicked young woman: "Don't give me any of that lily-white virgin' stuff, either, cause I know you got nothin' to lose."

That picture was actually a sensitive depiction of a rape victim's plight, but who would have known from the way an announcer ballyhooed it on the show that preceded it? He shouted, "Fear is going to come from the darkness! Next!"

In May, Jankowski told a meeting of the CBS affiliates in Los Angeles, "Being Number Two isn't enough. We want to be back where we belong in prime time - Number One. And we will be there again - even sooner than some people expect."

Obviously, CBS isn't planning on accomplishing this feat with quality programming ("Flying High"? "The American Girls"?), but perhaps it is felt that the public can be browbeaten into tuning in the tattered goods that CBS does have to sell. The network has disgraced itself and its once prestigious image and made clutter more than just an eye initant. It has made clutter a truly dirty word.