The $6.25 dividend recently declared by the Richmond, Fredericksburg & Potomac Railroad Co. is a quarterly dividend, not an annual one as reported in Monday's Washington Business. The Business section incorrectly reported yesterday that a decline in Planning Research Corp. earnings reflected losses in the engineering group and in PRC System Services. Only the engineering group had an operating loss. PRC System Services had an earnings decline but not a loss.

Planning Research Corp., based in McLean, has reported that earnings for its second quarter, ended Dec. 31, dropped 44 percent because of losses in engineering and system services.

Meanwhile, in other earnings reports, Baltimore Gas and Electric Co. announced a 16 percent drop in fourth-quarter profits, while Alexandria-based TransTechnology Corp. said its third-quarter profits were up 16 percent. And the Richmond, Fredericksburg and Potomac Railroad Co. rolled to a 15 percent earnings increase in 1984.

* Planning Research Corp., a diversified professional services company that does much of its business with the government, reported that its earnings for the second quarter dropped to $1.625 million (25 cents per share), compared with $2.885 million (40 cents) for the same period last year.

Revenue for the firm rose 7 percent to $81.77 million from $76.46 million during the same period in 1983.

Earnings for the first six months were down 65 percent to $2.275 million (35 cents) on revenue of $159.9 million, from $6.461 million (90 cents) on revenue of $156.3 million for the same period last year.

The company attributed the drop in earnings to income and revenue losses for the PRC Engineering Group and PRC System Services.

Weakness in the engineering group's international markets continued, while the systems services division was affected by higher marketing expenses and reduced revenue from its largest contract with the National Aeronautics and Space Administration, the firm said.

* Baltimore Gas and Electric Co. said its fourth-quarter earnings dropped about 16 percent to $36.13 million (74 cents per share) on revenue of $388.53 million, compared with $42.86 million (93 cents) on revenue of $380.89 million for the same period last year.

The company said the drop in earnings resulted from warmer weather and increased operating expenses.

Earnings for the year climbed about 13 percent to $243.915 million ($5.54) on revenue of $1.76 billion, compared with $216.453 million ($4.95) on revenue of $1.63 billion during the same period in 1983.

* TransTechnology Corp., which manufactures aerospace defense products, reported that its third-quarter earnings for the period ending Dec. 30 jumped 16 percent to $1.928 million (40 cents per share) on revenue of $25.86 million, compared with $1.661 million (34 cents) on revenue of $25.39 million during the same period last year.

For the first nine months, the firm said its net income rose 13 percent to $4.262 million (87 cents) on revenue of $73.189 million, compared with $3.784 million (81 cents) on revenue of $67.5 million during 1983.

* Richmond, Fredericksburg and Potomac Railroad Co. reported 1984 net income of $19.4 million ($54.08 a share). By comparison, the company earned $16.6 million ($46.61) in 1983. Railway operating revenue for the year was $57.5 million, a 4 percent increase over the 1983 level of $55 million.