"Sex, sex, sex. Sex, sex, sex, sex, sex, sex, sex." -- From "A Look at the '50s," by Al Carmines

AN EXPERIENCED Hollywood screenwriter who works occasionally in TV will never forget what a network executive told him when handing back one of the writer's scripts. The executive said, "Dirty it up a little, will you?"

It really happens.

And it's happened plenty this year:

On the premiere of "It's a Living" this season, a young waitress embarked on an expedition to lose her virginity at a mountain retreat.

On the premiere of "Secrets of Midland Heights" last night on CBS, a teen-age girl embarked on an expedition to lose her virginity on a hayride.

On one episode of "Ladies Man," a woman boss tried to seduce a male employe in her office. On another, the hero discovered a friend was homosexual.

On "Too Close for Comfort," a deranged daddy rides shotgun over the sex lives of two nubile daughters.

On the premiere of "Enos," the good-hearted rube of the title fell for a hooker and helped break up a house of prostitution.

On an episode of "Vegas," Dan Tanna fell for a call girl.

On "Eight Is Enough," papa feared his son had become a male stripper.

And so it goes.

For years, special-interest groups have been decrying what they have seen as the progressively more permissive content of prime-time programming. And for years, American viewers have pretty much ignored the moralists and made smash hits out of smarmy romps like "Three Company." Each year the complaints sound much the same. But this year, there's a difference: The complainers are the same people taking at least partial credit for the election of Ronald Reagan.

Jerry Falwell, the TV evangelist at the head of "Moral Majority," said this week that his group will be part of a coalition of "organizations and individuals" -- religious and non-religious -- who will pressure the TV industry to reverse the "trend toward sexual permissiveness, situational ethics and even outright obscenity" in network TV shows.

"The trend has never been so obvious as it is this season," Falwell said in a statement released Thursday.

He ain't seen nothing' yet.

NBC is about to unveil a new series that could make Knots Landing look like Sunnybrook Farm. "Number 96," which premieres Wednesday night at 10 on Channel 4 (with additional chapters set for Thursday and FRIDAY BEFORE THE SHOW GOES WEEKLY) MIGHT BE THE BLOCKBUSTER NBC President Fred Silverman is hoping for and desperately needs -- the kind of show that becomes a big fat national fad.

But there's also the possibility that "Number 96" will be the sort of landmark TV executives dread, providing crusaders with a battering ram to storm the network Bastille. Already "Number 96" has scored a dubious distinction: Probably no other network TV kshow was ever promoted with such single-minded sleazola; sex is often used to sell shows as well as products, but the networks usually try to be cunningly discreet about the pitch.

"Number 96" is a sex sell all the way.

NBC's randy swap-meet may not turn out to be the dirtiest TV show ever, and it is hardly likely to meet the legal tests for obscenity. But added to all the other sexy shows on television, and to commercials -- for designer jeans, perfume and other products -- that are themselves becoming increasingly and controversially suggestive, "96" could be the spark to set off firestorms of backlash already being fanned by right-wing religious groups.

ABC as much as said, "Aw, the hell with it" and, forsaking all pretense of subtlety, sent out sheafs of girly posters to TV critics as part of the told TV Guide his show about teen-age sex would be "hot stuff" and laughed, "I'm going to be the porno king of television."

It's as if the networks were deliberately playing into the hands of those who blame TV for every crisis facing family, sexual relationships and the institution of marriage in America.

Falwell was careful to say in his statement that in the effort to "clean up" TV, "particular programs will not be attacked" and "no effort will be made to remove particular programs from the air." But he did wave the possibility of a sponsor boycott in front of the networks, saying it would be "a last resort only."

The coalition against permissive TV will not be fully formed for a few months, Falwell said, but as a "necessary first step" in the campaign, a national pollster will survey the public for its views on what's offensive about television. Falwell says the method of persuasion to be used against the networks will be "quiet conversation" and "an appeal tologic and reason."

Of course, there is no scientific evidence to support the idea that television's glandular mind-set in any way contributes to moral decay or to the corruption of young minds.

But neither is there any scientific evidence to prove that it doesn't. Sexual Shangri-La

"Number 96" is essentially "Dallas" in a hot tub, dealing with the moorings and pairings of residents at an Los Angeles aprtment complex. It was adapted by American producers from a long-running Australian serial that began airing in 1972. That series lured viewers with such video kicks as frontal nudity. There'll be none of that in the American version. But according to NBC publicity and the show's producers, there will be:

A husband and wife who reach an agreement allowing the wife to experiment with other sexual partners.

A divorcee having an affair with a man half her age.

A young man who arrives at the complex expecting it to be a "sexual Shangri-La."

A tenant suspected of the "bludgeoning deaths of young women."

A male character who "dies in the saddle" on the third show while making love to a Hollywood starlet "who'll do anything to get ahead -- even act."

And dear Dr. Leon, a psychiatrist who hosts a sex-talk radio show and who, says NBC, "seems socially successful, but hides an astonishing secret." The astonishing secret is that he's a part-time transvestite.

Another inhabitant of 96 Pacific Way, where all the hanky-panky takes place, is a "TV minister" who has the habit of breaking one or two of the more conspicuous Commandments. Bob Ellison, a writer and the executive producer of the series, says from Hollywood that the minister will not be identified as a member of the so-called "Moral Majority" -- partly because "we're going to have enough trouble with those guys as it is."

Ellison and Allan Manings -- another writer and the supervising producer -- say that they are not unaware of the holy war religious groups are planning against what they consider filthy TV. "We do have a feeling that we're going to hear from them," Ellison says. "A lot of shows will."

"Not necessarily rightfully," Manings interjects.

"It's certainly going to happen," says Ellison. "All we can do is move ahead and do the show we think we should do."

It's hard to believe that only five years ago, CBS censors deleted the WORD "VIRGIN" FROM A "m*A*S*H" script (that was 25 years after Otto Preminger incensed the Motion Picture Association of America by permitting the word to be spoken in his movie "The Moon Is Blue.") One could say we've come a long way. One could also say we have gone too far.

Manings and Ellison are not specialists in sleaze. Both have backgrounds in superior TV comedy: Ellison on "The Mary Tyler Moore Show," Manings on "Laugh-In." They say "Number 96" will be the first serialized mix of heavy drama and strong comedy on network TV. But one insider who's read scripts calls the show "a really shallow piece of junk."

"A funny 'Dallas,'" Ellison calls it, then adds, "An intentionally funny 'Dallas.'" Manings says the Australian show not only had frontal nudity but also "a lot of overt sensationalism -- an incestuous relationship, a pantyhose strangler, stuff like that."

"All we kept was the title, changing '96' to 'Number 96,'" says Ellison, And the fact that it takes place in an apartment building." As for the naughty, ooh-la-la stuff, "You'll find more of that on 'Three's Company,'" he claims.

But the fact remains that the program promises to move TV's already liberalized sexual boundaries one step, if not a great leap, further. The motif for the NBC press kit is a keyhole. A panting starlet purrs in a promo that a cuddly-studly baseball player "can pinch-hit with me anytime." NBC publicity buzz-words the show as "daring," "outrageous" and "uninhibited."

The characters include, NBC says, a divorced man "eager to embark on a swinging singles life," a couple who "experiement with ways to spice up their marriage," a divorcee who "moves into Number 96 and sheds too many inhibitions," and a 20-year-old handyman who "misses no tricks."

Ellison says the show is sexually explicit "only within the confines of what is allowable on television and according to our own standards of taste. We're not trying to be salacious or to see what we can get away with." Maning says that on the show "people have sexual relations, sometimes with their own partners. But it's not a game of musical beds."

NBC's censors, still smarting from hundreds of complaints about the revamped "Saturday Night Live" and its dum-dum improprieties, are responsible, according to industry rumor, for the fact that "Number 96" has been delayed in production -- so delayed that, NBC announced Friday, it would not have a finished version of the program to show the press before airtime on Wednesday. But Mannings says the department of standards and practices has not been a problem. "We don't expect any interference," he says. "Not that we've asked for anything unusual."

"We're not doing things just for the sake of shock," says Ellison, "but if a couple agree to have an open marriage, and the woman is having an affair with another man, and the husband who helped make the arrangement walks in on them, she can say to the husband, 'You bastard!'" NBC censors, he says, will allow her to. "They backed us on that one."

"We're going to feel the water a little bit, see what we can do, where the audience takes us, what the public likes," says Ellison. "We're trying to be a little more adult than the other shows."

But if Ellison and Manings think they're testing the waters, there may be other viewers who think what they've done is open the flood gates. All the way.