Westinghouse Electric Corp. yesterday reported increased sales and earnings in the first quarter of 1985 over the same period last year.

Ameritech, operator of Bell telephone systems in five Midwestern states and a leading supplier of communications services in that region, also reported higher quarterly earnings.

Westinghouse first-quarter earnings were $129.7 million (74 cents per share) on sales of $2.31 billion, compared with 1984 first-quarter earnings of $116.6 million (66 cents) on sales of $2.27 billion. Per-share 1984 earnings were adjusted to reflect a 2-for-1 stock split last year.

"This gives us a good start on the year ahead," said Chairman Douglas D. Danforth. "While sales were up only slightly, productivity and quality improvements are contributing to higher operating margins."

Higher sales were recorded by the industries, energy and advanced technology and broadcasting and cable groups. Sales of the commercial group declined from the 1984 level, the company said.

Corporate operating profit improved, with broadcasting and cable showing the greatest increase. The energy and advanced technologies group also had a better performance, while the commercial group was lower, the company said. Other income increased slightly over last year's first quarter, including higher income of Westinghouse Credit Corp..

Ameritech reported earnings of $274.3 million ($2.80) for the three months ended March 31.

First-quarter earnings increased 6.5 percent compared with the first quarter of 1984, Ameritech Chairman and Chief Executive Officer William Weiss told the company's first annual shareholders' meeting.

"The driving force behind the increase was demand for our services from businesses throughout our five states, a strong indication that the Midwest economy continues to prosper," Weiss said.

Ameritech operates Bell telephone systems in Illinois, Indiana, Michigan, Ohio and Wisconsin.

Revenues for the quarter were $2.21 billion, or 8.9 percent more than the first quarter of 1984.

Expenses were $1.62 billion, an 11.3 percent increase compared with the first quarter of 1984, partly due to higher depreciation of capital investments and wage and salary increases, he added.Caterpillar Tractor Co. reported a loss of $70 million in the first quarter of 1985, compared with a loss of $109 million in the same period last year.

Sales for the 1985 first quarter were $1.48 billion, a $90 million increase from the the same 1984 quarter, the Peoria-based farm equipment manufacturer said.

A Caterpillar spokesman said progress in reducing the loss between the first 1985 quarter and the first 1984 quarter was obscured because the company can no longer record tax credits related to U.S. losses. If the company had been able to apply normal tax benefits to the first quarter loss this year, the loss would have been $45 million, the spokesman said.

On a per-share basis, the improvement would have been from a loss of $1.15 to a loss of 46 cents per share. The company now has $181 million of unrecorded U.S. tax credits that will be used to offset tax expense on future profits.