What do lonely traveling salesmen do for relaxation? Not what you might think says Lorraine Zenka Smith. "According to the letters we get," she says, "these men are reading our magazine."

Smith is the editor not of some brawny, masculine periodical but rather of Rona Barrett's Daytimers, one of the half-dozen or so monthlies that concentrate exclusively and exhaustively on the afternoon soap-opera field, a world of its own.

Reading one of these magazines is like waking up in a mirror universe where the all-too-familiar names of famous people have suddenly been changed. These look like traditional fan magazines, complete with chatty stories and "candid" photographs, but who has ever heard of the people on display?

Instead of pictures of a lovelorn Cher, Deidre Hall proclaims "I'm Lonely and I Don't Function Well Without a Man." Instead of John Travolta, it's Tom Fuccello moaning "All of a Sudden Women Are Going Crazy Over Me!" And rather than John and Bo Derek mooning over each other, it's Mattnew Cowles and Kate Dezine fearlessly telling the world, "We Were Afraid to Fall in Love."

There are millions of rank-and-file Americans -- ranging from the stereo-typical cloistered housewife to Lorraine Smith's traveling salesman -- to whom those names are as familiar as their own. They are the ever-faithful watchers of television's soap operas. Their devotion has been rewarded with a flowering of magazines which, if not of superlative literary quality, boast circulations up into the half-million range and are fascinating for what they reveal about the soaps themselves and the readers who follow them.

Before there were soaps on television, before in fact there was such a thing as television, daytime serials like "The Second Mrs. Trent" and "Our Gal Sunday" were tremendously popular on radio. They even had a fan magazine of their very own, Radio Mirror. But when the soaps went off the air in 1960, Radio Mirror became Radio-TV 7irror, which soon became TV-Radio Mirror, each name change connoting a greater separation from the world of teary melodrama.

Watching this sad regression was a man named Paul Denis, soon to achieve a kind of immortality as the father of daytime magazines. Fifteen years ago Denis persuaded Sterling Magazines to include a daytime column, a fan mag first, in TV Picture Life.

Then came a successful series of Who's Who in Daytime TV anuals, followed ultimately, 10 years ago, with the first of the daytime TV magazines, edited by Denis and called, appropriately enough, Daytime TV. "It was such an obvious thing," Denis says modestly of his perspicacity. "We knew there was a big audience there, the Nielsens proved that, and it was just a matter of going after it."

Daytime TV had the field to itself for a while, but only a while, for by the mid-1970s the soundness of Denis' concept had become apparent to so many people that it spawned an enormous number of rivals, so many that the exact number, somewhere between 19 and 28, is still open to dispute.

So a natural attrition process set in and now there are only some seven soap-opera-oriented publications on the market, ranging in circulation from about 100,000 to Soap Opera Digest's 525,000,

The soap magazines seem at first glance to be almost identical in content. All publish more or less breathless interviews with "the stars" and tidbitty gossip items on the order of revealing that Brenda Dickson of "The Young and the Restless" is in real life married to "the fabulously successful dentist Dr. Robert Rifkin," as well as every magazine perennially most popular feature, letters from the humble reader.

Ruth Gordon, executive editor of Soap Opera Digest, believes what sets her publication apart from the crowd is obvious enough. "We are the only magazine that tells the complete day-by-day synopsis of every single show," she boasts, pointing with pride to the three writers who watch the shows in the office as well as the backup writers watching at home, all of whom contribute to plot summaries like "Ada frantically called a doctor who decided that Rachel had to be rushed to a hospital!!!! Meanwhile, Blain is in a stew."

With a loyal readership that has made it the top-selling soap magazine, the Digest feels it does not have to besmirch its hands with the gossip-mongering of its rivals. "There are some magazines that believe gossip is of primary interest to the reader, but we keep it to the point where it's not harmful," insists Gordon somewhat primly.

As for Paul Denis, still in charge of Daytime TV after all these years, he says his magazine, in addition to the continuing glory of being the first in the field, in different because "we are loaded with facts, we sell facts rather than bull-throwing or emotion.

"What we do is bring the show and the viewer together. The viewer falls madly in love with a character and she doesn't know a thing about the him. Because the credits roll very fast, she doesn't even know his real name. We give the actors an identity."

Be that as it may, Lorraine Zenka Smith, editor of Rona Barret's Daytimers, feels her magazine does even more. "We're the slickest; you're not ashamed to pick our magazine up. We're definitely a class operation in the fan field," she says. This touch of class extends to what the magazine offers -- more big-color heartthrob photographs than the competition -- as well as to what it does not: unsightly advertisements.

"We have none of those tacky ads, no bust builders, nothing, "Smith says tartly. "The other magazines have a 'back yard'-- it's downhill from page 30 on. We have stories all the way through the book." Except for frequent house ads, that is, but, Smith explains, "they're classy."

If the editors unite in one thing, it is, as might be expected, in defense of their readers. "I used to think they were a bunch of dum-dums myself, to tell you the truth," Smith says, but she has learned differently.

"It's not just the stereotypical housewife who sits home with curlers in her hair waiting for the kids to come home from school," says Tv Dawn to Dusk's Sherry Amatenstein, with Denis stoutly adding, "We get letters from very literate readers. We can tell by the quality of the stationery."

As for geographic distribution, that's not what you might expect, either Smith says that most of her readers come not from rural areas but from bit cities where more TV tations mean more soaps available for viewing. Paul Denis' readers come largely from Sunbelt retirement areas, though Washington -- "Maybe it's politicians who have nothing better to do" -- figures inexplicably high in the circulation totals.

Most surprising of all is the sizable readership these magazines enjoy overeas. "Six soaps are seen in Australia, three in New Zealand, and people in the Caribbean tune in from Florida," Denis explains. "And we have a big circulation in Germany. It's wives of GIs who miss the soaps and read the magazine to keep in touch."

The touching loyalty of these readers points up their most characteristic trait: The essential thing that sets them apart from their nighttime counterparts is a till-death-do-us-part fealth to their soap-opera heroes.

"In prime time you see the actor for an hour, he solves a problem and it's goodbye, while in a soap the actor shows up 260 times a year, which makes for a great delineation of character," explains Paul Denis. It also makes for viewer identification so strong that the soap character is perceived to be nothing less than a member of the family.