At Automatic Data Processing Inc. yesterday, callers on the chairman's telephone were greeted with, "Sen. Frank Lautenberg's office."

The newly elected Democrat from New Jersey soon will be moving to the Capitol from the boardroom in Clifton.

In his campaign, Lautenberg stressed his business background, asserting that he knew how to create jobs and to deal with the shift to high technology industries.

In taking the seat left open by the resignation of Harrison Williams, Lautenberg will leave behind a company he helped build into a $600 million giant of the data-processing industry, offering a variety of computerized accounting and record-keeping services to businesses that don't want or can't afford to purchase their own computers.

In his tenure with ADP -- more than a quarter century in all, including 13 years as president and seven as president and chairman -- the 58-year-old Lautenberg has won high marks from analysts and business associates for his business acumen and for guiding the company above the data-processing services companies that bloomed in the 1960s to its position as the industry's largest.

"They were one of the wonder companies of the '60s that actually made it," one analyst said.

Lee Margosian, an analyst at Wood Gundy Inc., rates Lautenberg's managerial skills as "excellent -- just look at the record."

"He's a terrific manager and hopefully will be a terrific senator," said Barry Bosak, an analyst at F. Eberstadt & Co. Inc.

"The bottom line of any businessman is how well he has done, and one must conclude that Frank Lautenberg has done very well," said economist Alan Greenspan, who sits on ADP's board. "The record of that company is just extraordinary."

"This is clearly an above-average businessman," Greenspan added. "His major strength is that he is very smart. His weakness is that he's a Democrat."

Lautenberg, who started out selling insurance, joined ADP in 1953, shortly after its founding by two brothers who were accountants. They had started the company to provide accounting services -- done by hand -- to other firms, but soon began applying computer technology to the work.

While the company added size by acquiring smaller data-processing concerns over the years, Lautenberg's primary responsibility was marketing. "He was principally responsible for building their marketing organization," said Lucien Vrigile, an analyst at Value Line. "They have a very strong record of sales growth."

Acquisitions and internal growth contributed to the expansion of a company that now has nearly 100,000 customers in all areas of finance and industry.