A woman's lilting voice now answers the telephone, "The Embassy of the Provisional Government of the Islamic Republic of Iran." Posters of the Ayatollah Ruhollah Khomeini, his eyes lowered into the long cotton of his beard, are hung on the ice-blue front walls of the Massachusetts Avenue chancery.

Inside, the guardians of power have changed. "In the name of God we are glad to announce the revolution is successful," is the way the representatives of Khomeini, their heads lowered, begin their first press conference.

Some faces are familiar -- a Georgetown rug merchant, a Houston doctor -- from the leadership of the last decade's marches against the rule of Shah Mohammad Reza Pahlavi.

But one former protester, Shahriar Rouhani, a 29-year-old doctoral student at Yale University, has clearly emerged as the ayatollah's man in Washington.

"We have been told to follow previous trends and policies, to maintain friendship with the American people, a friendship we firmly believe in," said Rouhani, showing a cagey skill at handling reporters' demands to know whom he talked to, what the means of communications with Tehran was, at what time...

For this task of point man in Washington, Rouhani would seem to be the ideal selection of Madison Avenue. He's outgoing, cordial, handsome, impeccably tailored in a three-piece navy suit. He speaks in measured terms about the volatile Iranian stuation and the fruits of revolution. "The ayatollah has been my hero since childhood. He represents the supreme definition of activism," said Rouhani in a hushed voice.

Around Rouhani moved the lively commotion of transition -- some of the new embassy staff wore name tags -- but Rouhani didn't appear to be distracted. "The victory did not happen fast enough," he said. "Its quickness only astonished those who did not know the movement."

Four weeks ago Rouhani came to Washington from New Haven, Conn., set up headquarters with the other pro-Khomeini groups at the Georgetown Holiday Inn, and began briefing businessmen, congressional staffers and the press.

On Sunday afternoon, the pro-Khomeini diplomats, led by Rouhani and Jalil Zakrabi, who technically replaces former Ambassador Ardeshir Zahedi, took over the embassy. They used a hacksaw to enter Zahedi's office, then removed a portrait of the shah's family. Rouhani ordered them not to place a framed picture of the ayatollah on the same hook.

"It can be lower," said Rouhani.

When the group picked up messages, from President Jimmy Carter and other American officials, on Zahedi's desk and started to ridicule them, Rouhani cut them off.

But each time Rouhani mentioned Zahedi's name in the press conference, he scathingly pronounced it "czar-hedi." At one point, answering a question about records of lavish spending, he sneered: "Obviously the friendships (of Zahedi and Americans) did go beyond the caviar and champagnes. But it is not our will to make trouble, to make enemies."

His emergence as the spokesman for the ayatollah came after 11 active years in the Khomeini movement, which he joined "when I was still in high school. It proposed a multi-dimensional world outlook, internal tranquility and external dynamism."

Yet, like generations of radicals, Rouhani kept his activism secret from his parents. "My father is an engineer and my mother an activist in charity work with the mentally retarded. But they are apolitical, not for or against," said Rouhani. "When they found out about my involvement, they were scared. Suddenly they realized that all the parties I told them I was at were not parties."

Ten years ago he moved to the United States, attending several schools -- on scholarships, he said, not on the shah's educational coffers.

"Immediately I had a full-time political role, all the time trying to be a good student," said Rouhani. He attended Georgetown University briefly, earned a degree in physics from the University of California at Berkeley, and is completing his doctorate work in fluid physics at Yale.

The cross-disciplinary approach of the American schools is one of the notions he likes in America. "I have been able to research and write on social psychology, the question of family systems," said Rouhani.

When the shah visited Washington in 1977, prompting the largest-ever dissident and supportive demonstrations for his rule, Rouhani was absent. "My parents were here receiving some medical treatment for lung troubles," he said. But he is a veteran of many of the masked demonstrations and was a leader of last fall's march on the 25th anniversary of the coup that brought the shah to power. "Often I thought the demonstrations were counterproductive," he said. "But that one was successful and my role was minor compared to the struggle in Iran. Outside we are merely trying to get some understanding."

Only last fall did Rouhani -- the grandson of one of Iran's major philosophers, Sheikh Esmaeil Mahallatti -- meet the ayatollah.

"He was charismatic. And I am a very skeptical person; I do not give credit unless it's deserved," said Rouhani. "We spoke of politics but I can't give you the details. But while I was waiting a Persian villager came up to the compound in France and he and I could not communicate our ideas. I, I guess, have been wrapped up in intellectual activities. But when the ayatollah came, they conversed and understood one another.

"That showed me he wasn't removed."

During the last few days' violence in Tehran, Rouhani has kept in touch with his family at home. "I feared for their lives -- oh boy, it did make me want to be home. But their spirits are high," he said.

Perhaps the personal links with the turmoil caused his grim presentation at one press conference. He did not smile, though the press chuckled, when he announced, "Oil is a Godgiven gift; we wish to share it with the world." But he did smile slightly when one of his colleagues was asked if they had found proof that the shah paid for the pro-shah demonstrations in the United States.

But his first days as the ayatollah's man in Washington were spent in taking care of business, running off to the MacNeil-Lehrer Roport television show, examing personnel records to determine the embassy staff's loyalty. All the while his wife, 18-year-old Lily Rouhani, an Iranian studying in America, was filling in as a secretary, her head covered in a traditional scarf.

"I do want to return home but I am a soldier, a servant of my people. If they want me here, fine; if they want me to research, I will."