Sears, Roebuck & Co. today unveiled detailed plans for a new type of consumer credit card it hopes will help make it a major player in the financial services industry.

The card, to be called "Discover," is designed not only to serve as a conventional credit card accepted by a wide variety of stores, restaurants, airlines and other establishments across the country, but also also to serve as a financial planning tool.

For example, Discover can be used to set up a family savings account in which interest rates would rise as the balance increases. Additionally, the Discover card could enable a person to set up a self-directed Individual Retirement Account with Sears' Dean Witter Financial Services Group with no set-up fee required.

The card also will give its members instant access to cash through automated teller machines across the country. Sears currently is negotiating with electronic banking networks already set up to give its customers access to the automated teller machines.

"Discover will be more than just another credit card," said Edward A. Brennan, president and chief operating officer of Sears. "It will be a true financial services card. . . . Consumers will be attracted to the product because it will help them save -- as well as spend and invest."

For the 99-year-old retailer, the credit card represents "a natural step in our evolution," Brennan said, noting that its unveiling comes only four years after the company entered the financial services field with its acquisition of Dean Witter and Coldwell Banker Real Estate Group.

By diversifying into financial services and by establishing 300 financial centers in its retail stores, Sears believes it can significantly increase its business opportunities. It hopes it will not only draw more customers into its stores -- and more frequently -- but also that its national reputation will encourage its loyal clientele to invest through Dean Witter and buy houses through Coldwell Banker.

"Our goal is to build a long-term relationship with our traditional customers," Brennan told more than 300 financial analysts during a six-hour meeting.

For now, at least, Sears is banking on its Discover card as a way to boost its revenue and earnings -- despite the highly competitive and established market that already exists in the credit card industry.

Today, more than $116 billion in sales are rung up annually under Visa and Mastercard. Sears, on the other hand, does only $13.6 billion a year under its Sears credit card.

Brennan, however, is confident that the company will succeed. "More than 40 million households shop our stores and catalogues; more than 60 million individuals carry a Sears credit card; 128 million people -- three out of four American adults -- will visit our stores this year. . . . Who else can leverage off that great base, which is roughly 50 percent of American families?" Brennan said.

Sears plans to begin testing Discover this fall in Atlanta. If successful, "by this time next year we would be moving along" and making it nationwide, Brennan said.

Brennan acknowledged that the card was a rather expensive undertaking that would not be expected to begin paying off until 1988.

Notably absent for most of today's meeting was Sears Chairman Edward R. Telling, who spoke only for a few minutes at the very end of the session. Telling, 65, noted that he is planning to retire before the end of the year and that therefore his absence was "intentional. I wanted you to see and hear the people who will be running the company after my retirement."

Discover's announcement came just one day after Sears, the nation's largest retailer, released its latest financial results, which showed only a modest gain for the quarter that ended March 31. Profits rose 4.4 percent to $223.3 million. Among its operations, the Sears Merchandise Group had the poorest performance, recording a 6 percent drop in profits from $81.6 million for last year's first quarter to $76.5 million this year.

"We face an extremely competitive environment, characterized by accelerating promotional activity," said William I. Bass, chairman of Sears Merchandise Group.

In an effort to improve the group's balance sheet and its competitive position, Bass noted a number of steps Sears' retailing division planned to take over the next few years. These include

* Opening substantially smaller new stores in rural areas where Sears traditionally has not had a large presence. Now being tested this year, the small stores are scheduled to become an important part of Sears' marketing strategy with perhaps as many as 350 small stores being established.

* Introducing for the first time brand-name goods such as Sony and RCA televisions into its stores to be sold along with its traditional Kenmore line. In areas where Kenmore products do not have a large share of the market -- such as color TVs -- Sears plans to sell other manufacturers' goods to draw more customers into Sears stores.

* Placing a greater emphasis in selling "hard goods," such as dishwashers and washing machines, to the commercial sector, including developers and owners of apartment buildings and condominiums, to offset the decline in durable sales, which account for a large part of Sears' revenue.

* Increasing its attention to specialty stores. While the company has for the moment stopped expanding its successful Sears Business Center stores until the volatile computer market settles down, it plans to rapidly expand its small paint and hardware stores. With 11 stores now in operation, Bass said Sears soon plans to open as many as 60 stores in four major metropolitan areas. Although Bass declined to name any particular market, Sears officials said the Washington area is being seriously considered as one of the target markets.

Sears will "explore all viable opportunities in the specialty marketplace -- whether through expansion or, possibly, acquisition. . . . The door is open" for Sears to buy another retailer -- specializing in home fashions, housewares, wearing apparel or other lines.

"I don't think the door has been open before," Bass said. Preferably, he added, he would prefer that Sears build its own specialty stores, but he said if the right opportunity came along, Sears would be willing to buy a small company and help it expand nationally -- and not necessarily under Sears household name.