There were no signals of white smoke from the American Telephone & Telegraph Co. board room yesterday but the selection of a new chief executive of the telephone company occurred with all the secrecy that surrounded selection of a new pope.

Timing was the only element of drama yesterday - because most people had not expected John deButts to give up early a job he obviously has relished.

There also was universal praise for Charles Lee Brown, the man named to take charge of the nation's largest private employer, the provider of 80 percent of U.S. telephone services and a company under attack by competitors and the federal government for alleged monopolistic practices.

A 1943 graduate of the University of Virginia, Brown holds an engineering degree. He began working for AT&T after Navy service in World War II. He served in the company's long-distance business in a number of cities before becoming an Illinois Bell executive in 1963.

He has been at 195 Broadway, AT&T's headquarters tower in lower Manhattan, only since 1974 when he became an executive vice president. His superiors obviously were impressed, and they put him in a select group of potential future chief executives in 1976 when he was named vice chairman and chief financial officer.

Robert LaBlanc, an analyst for Salomon Brothers, said yesterday that deButts in "leaving the shop in excellent hands." La Blanc called Brown, who takes over Feb. 1, "a real intellectual and sharp as a tack. AT&T has now got a guy young enough so that all of the major problems the company faces over the next seven or eight years - the transition from monopoly to competition, the antitrust case which they have to fight tooth and nail, and the total reorganization of the company - will come under the leadership of Brown . . . it is hard to think of someone better qualified."

Brown won the respect of the financial community in November 1974 when he made the crucial decision to cancel a big bond offering when the Justice Department filed its antiturst case - an action still years away from being tired.

In addition, Brown "built very good bridges to the Financial community" during 1975 when he visited all major U.S. cities to talk with investors and brokers about a forthcoming public stock offering, said one Wall Street executive.

Brown has a reputation of being more aloof than deButts, who has displayed a pungnacious attitude when defending AT&T. Some communications industry experts in Washington said they believe AT&T will adopt a more cooperative stand on issues of competition under Brown.

But Brown emphasized yesterday at a new conference that because of the gains made under deButts, "I am not planning any 180-degree turns" in policy. "So far as the Bell System's policy on regulatory matters is concerned, I have had a say is shaping it and, absent changed circumstance, I don't propose to change it."

Brown did say that he thinks the Bell System is entering what he called "a new era of opportunity." When deButts had taken over in 1972, he emphasized boosting AT&T profitability and establishing a marketing orientation in a corporation that had been based for nine decades on providing services.

Yesterday, Brown had this to say about the challenge he faces: "To equip ourselves to meet (new diversified communications needs), we have recently undertaken a quite radical restructuring of our business . . . the change in our business that John deButts set aloof . . . Our restructuring will make us quicker to perceive and quicker to respond to customer needs."

Brown is a director of several companies, including chemical giant E.I. duPont de Nemolle's and Chemical Bank. He also serves on the boards of Presbyterian Hospital in New York and Harvard's Graudate School of Business. He lives in Princeton, N.J., with his wife, Ann Lee. A son, Charles, is a medical doctor in California.