Reaping the benefits of developing a braoder market for its services, NUS Corp. recorded increases in sales and profits to record levels last year.

The Rockville firm reported yesterday that earnings for 1978 rose 76 percent to $2.24 million ($2.26 a share) from $1.27 million ($1.28) the previous year. Sales are up 30 percent to $45 million.

At the same time, the consulting and management concern revealed that a lawssuit has been filed in federal court in Kentucky, claiming $31 million in damages from the company and alleging deficiencies in preparation of a report containing coal reserve estimates.

"The company intends to contest the suit vigorously," NUS said yesterday.

fourth-quarter sales rose to $11.5 million from $10.2 million but profits were flat at $309,000 compared with $304,000, or 11 cents a share in both periods.

NUS, which provides energy and environmental consutling and management services, has much of its work associated with existing nuclear and coal-fired electric generating plants while in the years prior to 1975, there was a heavy reliance on nuclear projects.

The company said it had a year-end contract backlog of $22 million compared with $21.8 million a year earlier.

Systematics General Corp., of Falls Church, reported operating profits of $190,000 (14.6 cents a share) last year compared with $249,000 (19 cents) in 1977, as sales rose to $4.9 million from $3.7 million, according to preliminary estimates. The cmpany said earnings were depressed by transitional probablems in expanding manufacturing operations.

In addition to the record rate of sales last year, the firm said the current volume rate is more than $7.5 million on an annual basis. Systematics General produces optical character reading machines and provides engineering services and consulting, among other operations.

Telenet Communications Corp., a Washington company engaged in operating a data communications network, reported a 1978 net loss of $5 million compared with a loss the previous year of $4.1 million. Revenues jumped to $8.9 million from $4.1 million.

The auditing firm of Coopers and Lybrand qualified its opinion on Telenet's statements because of a need for outside financing to continue operations. But near-term needs are expected to be met through a loan from General Telephone & Electronics Corp., which plans to acquire Telenets but is waiting for Federal Communications Commission approval.

Stanwick Corp., an Arlington management services company, reported that earnings increased in the nine months ended Jan. 31 to $1.66 million ($1.60 a share) from $1.18 million ($1.14) a year ago. Revenues rose to $16.3 million from $14 million. Third-quarter profits fell, however, to $231,423 (22 cents a share) from $304, 361 (29 cents).

Because of turnmoil in Iran, where Stanwick has been engaged in providing maritime services to the Tehran government, earnings from that operation have been stopped. In the recent nine months, about 77 percent of revenues were related to the work for Iran.

Stanwick has pulled its employeeout of Iran, and the company noted that it is uncertain when business can resume there.