They may be railroad mechanics, Navy engineers or lawyers by profession -- but it's not for these endeavors that they're stopped by fans in the neighborhood supermarket or razzed by family and friends.

It's for their television escapades.

On the cable television channels in Arlington, Alexandria and Reston, otherwise average citizens are becoming TV performers, some even neighborhood stars, through something called public access or local origination programming.

Their Nielsen ratings are nonexistent--but the performers don't have to worry about unhappy sponsors, either. The cable television channels on which they're broadcasting are noncommercial and reserved for public use.

No citizen wanting to put on a program has ever been turned down, the cable companies say. Come in with a script or idea, and they'll put you on TV.

"The future of public access is limitless," said Bob Gordon, public access coordinator for the Arlington Telecommunications Corp. (ARTEC), which operates Metrocable. "All people have to do is bring the imagination and we provide everything else."

This concept--making broadcast time available to citizens--has come of age as cable television has skyrocketed in popularity in recent years. Today, provisions for some form of public access generally are required before a jurisdiction will grant a cable franchise. And Northern Virginia is no exception.

Arlington, Alexandria and Reston all require their cable companies to set aside a channel for free public use. In Arlington, this is called a public access channel, meaning it's controlled by county citizens. In Reston and Alexandria, the cable companies have established "local origination" channels for this purpose, the difference being that the cable companies control what goes on the air.

But the difference is actually a fine line. In reality, there's been little control. So far, the cable firms say, they have not had any situations requiring censorship or testing "community standards." They follow the rules that the Federal Communications Commission applies to commercial broadcasting, although the FCC no longer regulates public access stations or even requires their inclusion in cable systems.

Citizen-performers, thus, are basically on their own. Men or women who want to climb aboard a soapbox and air their views or show off the results of all those years of tuba lessons have an outlet through public access channels.

They've been responsible for putting out to cable subscribers such programs as "Sprout a Garden in a Jar," "Men and Quilting," "The Tuskegee Airmen's Story: 1941-1948, Part One" and "The Cable Comedy Network."

The schools and local governments have their own channels to use for classroom presentations, broadcasting meetings or however they see fit. The public access stations are strictly for the people.

People who think Washington television stations slight local news can put on their own programs and report what they see their boards or councils doing about that controversial road widening.

Those upset with conventional medical treatments can air their own cure theories. Flower arranging, macrame or tap-dancing aficionados can produce 20-minute or hour-long specials.

Just as long as they're clean. No profanity, slander or copyright violations are allowed. Gambling shows are also out. Commercials are taboo. Blatant politics is prohibited, but political forums and debates--with equal time going to the opposition--are okay.

"Public access, used properly, can be a very valuable tool for keeping the community informed, particularly about minority opinions," said Hy Triller, vice president of the Alexandria Cablevision Company (ACC), which uses Channel 10 for such programming. "You always hear the majority opinions, but not the minority opinions. Public access can provide that tool, provide what I call 'narrowcasting'--focusing in on something of interest to a small segment of the community.

"(Network) broadcasters can't do that because it doesn't appeal to the masses. But we can do 'narrowcasting'; we can aim something at 10 customers. Who cares if (the audience) is that small? You can get things to the community that they wouldn't ordinarily see."

Unlike the Reston and Alexandria systems, ARTEC offers two levels of instruction for aspiring performers, directors and producers who want their talents aired on Metrocable's Channel 3, the public access channel.

The introductory level is free and runs for three hours on two nights each month. "If you can run an Instamatic, you can run this (equipment) after six hours of training," Gordon said of the classes that 360 people have taken since the channel opened a year ago. Instruction covers the basics of operating equipment such as cameras and lights and introduces students to the technical jargon of television.

The advanced level, which costs $40 and runs for three hours on five consecutive nights, involves scriptwriting and a lot more "hands-on" experience with equipment. Each student produces a short show at the end of the week. Graduates of this course, so far about 100 students, can then check out two of Metrocables's three cameras for productions, said David Pepper of Development Communications Associates in Alexandria, which provides the instruction.

Taking the courses, however, is not a prerequisite for putting on a program.

"If someone walks in off the street and does not want to take the training," Gordon said, "I would put them in touch with people who normally film. There is enough of a (network) here of people who have taken the training, who are very enthusiastic and willing to help someone else film."

A recent advanced-level class attracted nine persons, including Richard Taggs, an employe of Newsweek magazine's editorial staff, who has been serving as the film and entertainment critic on Leesburg cable television. "I've never actually worked behind the camera," he said, "so this seemed to be an interesting way to be introduced to the production and direction of films."

Another student, Bruce Wald, associate director of research for the Defense Department, said he took the course because he wants to put together programs about soccer. Vicki Barr, a Marymount College junior studying communications, said she simply wanted to learn more to bolster her career.

As a condition of winning the Arlington franchise in 1975, ARTEC had to agree to provide the courses. And, while the Alexandria and Reston cable companies have no such provisos in their contracts, they are not about to slam the door on people who want to learn production techniques because they, like Arlington, rely on volunteers to help put on some of the programs.

"We'll work (free) with anybody who walks in the door," said Tom Bartelt, local origination manager for Warner Amex Cable of Reston, where public access is on Channel 8.

Alexandria does things a bit differently. "Our approach is to supply the air time, equipment and people to do it," said Triller. "But if someone were to volunteer to help us, we would certainly use them."

The public access channels in Arlington and Alexandria have been in operation only about a year and, consequently, lack the sophistication of Reston's, which went on the air in 1970. Reston, in fact, was designed with cable television in mind, Bartelt noted; rooftop antennas are forbidden.

Because it has been on the air longer and has a larger pool of experienced volunteers to draw upon, Reston's programming is more extensive and polished. Just because a program is on a public access channel, Bartelt said, "doesn't mean it has to look amateurish and hokey. It doesn't have to look like someone's stereotypical home movies."

Reston's programs run Sunday through Thursday nights from 7:30 to 11 and Tuesday, Wednesday and Thursday mornings from 10 to noon. While the station does rerun some shows, Bartelt estimates it airs 400 hours of new programs annually.

This costs the Reston system about $100,000 a year, Bartelt said, including the salaries of a staff of five. The station has five cameras and a mobile van, so it can cover community and sports events anywhere.

"There are times when we say, 'Is anybody out there watching?' " Bartelt said. "But we're trying to put on programs of local interest and it doesn't matter how many are watching. We're not attempting to beat out the networks." The Reston system has about 8,400 subscribers, or 60 percent of the households.

Alexandria, which also has a mobile van and four cameras, runs at least three hours of programming weeknights in prime time and has spent nearly $300,000 equipping and operating the station in its first year, Triller said.

"We absorb all the costs (of producing)," he said. "Rather than give $100,000 to the community and say, 'Here, you run it,' we have provided everything. They have a television station all their own to use, and we staff it."

"We could go anywhere (to do a show) any time we wanted," he said. "The only limitations are that the equipment can't be two places at once." But so far, he said, the demand on the new system has not been overwhelming. Triller estimates that about 40 people have asked to put on shows; ACC has 12,500 subscribers, or about 37 percent of the households.

Because the demand has not been extensive, the separate channel designated for public access (27) has not been activated, Triller said. Sports, reruns of City Council meetings and citizen shows currently all run on Channel 10, but they could be rerouted to their designated channels if programming fills out, he said.

Of all the local cable systems, Arlington's has been the most criticized for delaying the advent of a public access channel. That controversy has abated recently, however, and ARTEC is preparing to turn channel 3 over to a Citizens Access Corporation (CAC) which will be formed in the next few months.

Joseph D. Lewis, chairman of a special committee drafting bylaws for the CAC, said the new corporation would run the system, which will be operated out of a new studio at George Mason University Law Center near the Virginia Square Metro stop. ARTEC has 21,400 subscribers, representing 38 percent of the county households.

ARTEC, which just had its franchise rights extended to 1995, is committed to paying $170,000 for equipment and another $40,000 to renovate the studio, Lewis said. In addition, the company must pay $75,000 for general operating costs and provide a $12,500 matching grant for any money the CAC raises from the general public in the first year. After that, the amounts increase annually.

Programming, still very limited, is scheduled from 6 to 9:30 p.m. on Tuesday and Thursday nights, but even that time is rarely filled, Gordon said. More time can be added as needed, he said, but the demand hasn't been that great.

"I hope the CAC will push for big-time recognition," Gordon said. "It's difficult to get publicity for public access, but the future is limitless. It's going to depend on the imagination, commitment and support the CAC is able to bring with them. They can take it in any direction. It can be a fantastic success . . . or it could bomb."