American Telephone and Telegraph Co. and a group of seven telephone terimal equipment suppliers yesterday announced the settlement of a six-year-old antitrust case under terms that its competitors say could restructure the way the manufacturers do business.

Although the plaintiffs had asked a federal court here for $300 million in damage, the settlement involves no money, and instead calls for AT&T to set up new methods for handling the problems of these firms. The companies manufacture equipment such as business switchboards and internal office switching devices.

"I am hopeful that this settlement will take a long step toward eliminating friction between interconnect vendors and the Bell System," said Edwin Spievack, an attorney for the AT&T competitors.

Precise details of the settlements are confidential, but the two sides explained that the plan calls for AT&T to set up in each of the 24 Bell System operating companies an office to serve as a contact point for AT&T and users and sellers of the equipment. This office would handle requests for installation, schedule the delivery of Bell services and manage the cutover of service from Bell equipment to that of the competitor.

Previously, these arrangements were handled by AT&T marketing departments, a situation that Spievack said resulted in conflicts between the competitors and AT&T operating personel.

If AT&T does not enforce the termms of the agreement, the companies could sue Bell for violating the terms of the settlement. But Spievack said he has "a feeling that they'll carry through on this one."

The suit was filed in Novermber 1974 by Jarvis Inc. of Richmond, Va., and six other firms, charging that AT&T and its subsidiaries -- Western Electric Co., Bell Laboratories and one operating company named, for jurisdictional reasons, Chesapeake & Potomac Telephone Co. -- were trying to run them out of business.

The suit also charged that the tariffs that non-Bell manufacturers were charged were artifically high and had the effect of limiting the firms' ability to sell their products. It was scheduled to go to trial early next year, but as a result of the settlement, which followed 10 months of negotiations, the case has been dropped.