The Rouse Co. yesterday reported a $3.4 million loss in the second quarter, citing delays in land sales, higher expenses and a one-time gain that inflated comparable results a year ago.

In the 1989 second quarter, Columbia, Md.-based Rouse earned $4.1 million (7 cents a share). Revenue in the quarter rose 3 percent, to $120.5 million from $116.9 million a year earlier.

For first six months, Rouse posted a $3.97 million loss, compared with earnings of $5.3 million (8 cents) a year ago. Revenue for the six-month period rose 4 percent, to $238.9 million from $230 million in the same period last year. The year-ago first-half results included one-time gains from the sale of assets, totaling $5.1 million.

Rouse, well known for its creation of the planned community of Columbia and such retail-restaurant complexes as Baltimore's Harborplace, said the delayed land sales involved properties in Columbia. It said its earnings before depreciation and deferred taxes on operating properties rose 13 percent in the first half.

Iverson Technology Corp., a McLean-based computer systems maker that is shifting to commercial markets and away from defense contracting, said yesterday that that effort led to a first-half loss and a drop in second-quarter earnings.

The company reported a first-half loss of $992,900, compared with a profit of $302,800 (8 cents a share) in the 1989 first half. Its revenue fell 16 percent in the half, to $20.2 million from $24 million.

In the second quarter, Iverson said it earned $87,600 (2 cents), down 58 percent from a $210,400 (6 cents) profit in the 1989 second quarter. Revenue rose 15 percent in the quarter, to $14.6 million from $12.75 million.

Iverson said the salary and advertising costs related to entering the mail-order and telemarketing business for personal computers boosted its expenses in the second quarter.

Although its newest General Services Administration schedule includes more computer products that it can sell to government agencies and their subcontractors, Iverson is seeing a dwindling market for one of its specialties -- computers made to the federal government's Tempest standard for protection against electronic eavesdropping.

Sales under its computer systems integration contracts with two large government agencies remain steady, Iverson said.

Isomet Corp., which makes laser systems and laser accessories for a variety of purposes, said its losses widened in the first half and second quarter.

The Springfield-based company said it lost $300,000 in the second quarter, compared with a $132,000 loss in the 1989 second quarter. Revenue declined 6.5 percent, to $1.8 million from $1.92 million.

Isomet lost $343,000 in the first half, compared with a $50,000 loss in the same period a year ago. Revenue rose 5 percent, to $3.66 million from $3.48 million.

Universal Security Instruments Inc., an Owings Mills, Md.-based company that makes and sells consumer video, telecommunications and security products, said a joint manufacturing venture helped boost its profit 127 percent in the fiscal first quarter ended June 30.

A company spokesman said the joint venture's higher profit margins helped offset the impact of a March 28 fire that destroyed Universal's plant and administrative offices in Owings Mills, reducing some of its manufacturing capacity and destroying inventories.

The fire was responsible in part for a 20 percent decline in revenue during the quarter, to $5 million from $6.24 million.

Earnings totaled $121,974 (4 cents) in the quarter, compared with $53,688 (2 cents) in the same quarter a year ago.

The latest joint venture, involving a Hong Kong manufacturer that Universal declined to identify, produces telephones, smoke detectors and video products.

The company said it expects major revenue growth from the introduction of a new product, a wireless broadcast system that lets a single videocassette recorder be connected to several television sets in a home.