Carolyn Mar is talking on the phone to a woman she's never met. The caller is fed up with her violent husband and in love with another man, but afraid to move out because of a young child. She wants Mar's advice.

"What can you say?" Mar wonders out loud after hanging up.

Hers is the question that faces the volunteer staffers of the D.C. Hotline every time the phone rings.

What can you say to the teen-age drug addict threatening suicide? Or to the elderly woman battling illness in a lonely hospital room?

The usual exhortations--"Cheer up" or "Pull yourself together"--seem pointless, possibly derisive, to people troubled enough to seek help from anonymous strangers, says Mar.

"We're here to help people organize problems themselves," she says. For example, it turns out that the woman caller "had already decided to leave her husband," says Mar. "She needed someone to tell about the decision, not advice."

The D.C. Hotline is one of the more than 30 organizations in the Washington area that provide emergency information, counseling or just sympathy over the telephone.

Many of the crisis lines specialize in certain issues such as child abuse, rape or homosexual rights. The D.C. Hotline is the city's most broad-ranging and offers a referral service to 400 agencies, dealing with "every conceivable thing that could go wrong in a person's life," says director Sherry Cummings.

What most of the services have in common is that they are staffed by volunteers like Carolyn Mar, whose only reward for her sometimes harrowing work is an occasional note of hope in a faceless voice at the other end of the line.

"They have to get satisfaction by sharing their caring, from just knowing that they're trying to help someone put a hole in a sense of hopelessness," says Cummings, 27, a four-year veteran at D.C. Hotline, a private nonprofit group with an annual budget of $35,000 and only two paid administrators.

"It's the Peace Corps mentality that attracts many of us--'Help people help themselves,' " explains George K., 26, who asked that his last name not be used so that he will not receive Hotline calls at home.

A law student at Georgetown University, George K. has worked for the Hotline for 3 1/2 years and says he is typical of the service's 70 volunteers: "young, professionally oriented, liberal-minded, people-oriented."

They handle more than 14,000 calls a year from a cramped two-room office on Massachusetts Avenue downtown. Cummings asks that the exact location remain secret to protect against pranks or abuse of staffers.

Two lines are open on weekdays from 1 p.m. to 1 a.m., longer on weekends. By mid-evening on a recent Tuesday, the phones were ringing steadily.

George K. picks up several times in the space of half an hour only to hear a quick click and a dial tone.

"Probably wants a woman," says Sharon Parente, who is waiting to begin her four-hour shift.

The most frustrating problem facing female volunteers is repeated calls from men who clog the lines with heavy breathing or abusive tirades stemming from sex-related problems.

"You feel really stupid, trying to help someone, when you realize they're taking advantage of you," says Parente. "We're not here for people to get off on, to be treated like garbage."

Assistant administrator Erik Weiberg estimates that 20 percent of the calls women answer fall into this category. "It's the biggest morale problem because it makes people ask, 'Why should I do this?' " he says.

"We're willing to help people with sex-related things, but not when they only call to abuse somebody," says Weiberg. "There's nothing we can do in that situation, so we tell those callers to call back after they calm down, or we just hang up."

"We all deal with the abusive calls," says Harriet Guttenberg, director of the Montgomery County Hotline, a similar organization in Maryland. "You can't always make the distinction, and we can't get too distracted by it."

More intimidating than interference from obscene calls, staffers say, are the encounters with genuine crises, and above all others, potential suicides.

Leonel Gomez spoke recently with an 11-year-old girl who said she had been raped by her father and wanted to kill herself.

"We want to give that person a thread she can follow and hold onto," he says, recalling the incident. The volunteers receive a minimum of 35 hours of training in preparation for such moments and can refer to a series of posters on the office wall reminding them to "establish rapport, explore the now, explore resources, and make an agreement."

But Gomez admits that "there is no magic, no great scientific technique" for the 3 percent of the Hotline calls which involve discussion of suicide.

Staffers always try to establish a potential suicide victim's condition and location so that medical help can be sent, says Gomez, though determined questioning may result in a caller hanging up.

Referring to the young girl's suicide threat, he says, "The toughest thing is you never know what will happen . . . It can be very painful."

To minimize the possibility of volunteer "burn-out," most staffers limit themselves to four hours of Hotline work per week. They hold monthly rap sessions which are half business meeting, half party. Cummings publishes a lively in-house newsletter filled with advice and pep talk.

"You have to look for the lighter moments, especially after a tough shift alone," says Gomez. He smiles, remembering a woman who called recently, frustrated by an overbearing elderly mother.

"We came up with the idea of giving the mother a puppy. Doesn't that make sense?" says Gomez.

The woman called back to thank him. "That's the most you can expect out of this," says Gomez, "the most you can want."

The D.C. Hotline telephone number is 462-6690.