When Fairfax County Police Officer Virginia E. Dalby received a call to go to the Rte. 236 bridge over the Capital Beltway last November, she found a woman threatening to jump off the bridge with her retarded son.

Dalby, terrified of heights, persuaded the mother to let her son go, but she knew her only chance to save the woman was to win her trust. "She kept saying I looked too young, and how could I know what I'm doing," recalled Dalby, 22, who had been with the police department only 1 1/2 years. The woman told Dalby: "Get up here, and I'll trust you."

Sitting precariously above the Beltway, and sometimes shouting over the traffic, the officer talked to the woman, who said she was distraught over her inability to get housing assistance. After 30 minutes, Dalby and the woman "took to each other" and she convinced the woman that her more experienced supervisor could also help.

"She let me put my arms around her," said Dalby. As her supervisor approached the guardrail, "we kind of pulled her. I've never been that scared. I really haven't."

For her "empathy and sensitivity" on Nov. 21, 1985, Dalby was recently honored, along with 13 other public safety officers, at the eighth annual Valorous Service Awards ceremony. The awards luncheon, sponsored by the Fairfax County Chamber of Commerce, honors heroism above and beyond the call of duty in the police, fire and rescue and sheriff's departments.

On the podium at the Springfield Hilton, Dalby glowed as she was presented with the Bronze Medal, given in recognition of acts involving unusual personal risk or unusual judgment, zeal or ingenuity in an emergency situation.

The Gold Medal, the top honor for an act involving extreme personal risk, has never been awarded. This year there were two recipients of the Silver Medal, awarded for acts involving great personal risk.

Dalby said she still talks about three times a week to the woman whom she helped rescue. A social worker has been helping the woman with her housing situation, she said, and the woman's 17-year-old retarded son has a part-time job.

Of her award, Dalby said she was surprised. Of helping the woman, Dalby said: "It was just the nicest feeling in the world."

Other recipients, chosen by a panel of citizens from nominations by public safety officials, were:

Sgt. George L. Sisson, fire Company 30, Merrifield. Sisson received the Silver Medal for crawling into a burning house with "total disregard for his own personal safety" and saving two elderly victims trapped inside.

Police Officer Ralph R. Scott, West Springfield District Station. Scott received the Silver Medal for ordering an armed man holding a doctor and nurse hostage to lay down his gun. The suspect hesitated, pointed his gun at Scott, and then surrendered.

Bronze Medals were awarded to Officers Stephen R. Scherr, Joseph D. Welch, and Master Officer Stanley H. Shaner, all of West Springfield District Station; Officer Timothy W. Field, Reston District Station; Officer Paul S. Crossfield, Mount Vernon District Station, and fire Lt. Bernard D. Bickman, Company 26, Edsall Road.

Honorable Mentions were awarded to Lt. William R. Kingdon, Sgt. Timothy R. Jeter and Firefighter I Eugene W. Beach, all of Company 2, Vienna.

Lifesaving Awards were presented to Firefighter John L. Leete, Company 34, Oakton, and Michael Guditus, Emergency Communications Assistant II, Emergency Operations Center.