Every weekday morning, Patty Hrin sits at a desk in the basement of an Arlington County government office building, silently feeding official county documents into a microfilming machine.

It is a task that would bore most people to distraction. Feed the paper, stack the film. Feed it, stack it. Do it again. And again.

The job is never more or less than that. It cannot be done creatively, or artistically, or cleverly. It can merely be started and finished.

But in her blue dress, with flowers pinned in her hair and a a huge grin plastered on her face, Patty Hrin feeds and stacks, feeds and stacks. The job is her future -- something she didn't always have.

Patty Hrin of Arlington has had Down's Syndrome and a serious case of mental retardation since she was born 21 years ago. Until recently, there would not have been any way Patty could have functioned in an office environment. The only future she could have looked to was a life of being warehoused -- at home if she was lucky, in an institution if she wasn't.

But since December, after a year of training, Patty Hrin has taken a bus and a subway each way to work. In her three hours a day at the office, she has made friends, mastered the office routine, even learned to flirt with the men in the print shop down the hall. She has done so well that, starting next month, Patty will jump from 15 hours of work a week to 30 -- nearly full-time status.

Patty is the only Down's victim now employed by Arlington County, and a check of area governments indicates that she is the only one working regularly for a local government.

But Patty Hrin doesn't know that, or care. "I love it," she says. "I just love it, that's all."

Patty's job and her preparation for it are largely the work of Janis DePoy, a 37-year-old teacher at Jackson Special Education School, the only public school in Arlington County exclusively for handicapped students.

"She has an IQ of 55, but that's really misleading," DePoy says. "The key thing to understand about Patty is that she only has a 'survival vocabulary.' She can ask you where the bus stop is, that sort of thing. But introduce even a moderately complicated problem, and she can't deal with it."

For example, it took about a week for her fellow microfilmers to explain to Patty the buttons along the base of the office phone. Patty kept pressing the intercom button instead of one for an outgoing line. Seven office lines rang each time Patty tried to place an outside call until Marc Gleaves, Patty's supervisor, set her straight.

Nevertheless, Patty concentrates so well on a job that others find beneath them that she is "an ideal choice. Her mind never wanders. She's doing fine," Gleaves says.

Very few Down's victims can expect Patty Hrin's future: an apartment of her own if she wants it, a job she can do well and a place that is willing to hire her to do it. According to DePoy, perhaps half of all Down's adults can be trained to the point of being employable with minimum supervision. But that is not the same as saying that the Real World is ready to hire them or that they are ready to cope once they're outside the "special education cocoon."

Still, to watch Patty Hrin feeding and stacking, feeding and stacking, one thing is clear: Arlington County has set an example that every metropolitan government should follow.