Discontinued operations for the fourth quarter of 2011 include the operating results of RedBlack which was sold in the third quarter of 2012 and the final costs associated with exiting the Energy Services business.
All revenue, gross margin and operating expense amounts presented below represent results from continuing operations.
Revenue was $29.3 million, compared to $29.5 million for the fourth quarter of 2011, reflecting an increase of $4.8 million in Communications Systems sales offset by a $5.0 million decrease in Battery & Energy Products sales. Battery & Energy Products sales were $18.8 million, compared to $23.9 million last year, a 21% decline, reflecting for the most part the continued slowdown in the government and defense order rate for rechargeable and non-rechargeable batteries. Communications Systems sales were $10.4 million, compared to $5.6 million for the same period last year, an increase of 85%, reflecting the fulfillment of large orders for amplifiers from international defense customers and continued demand for amplifiers from the U.S. military. New business development during the year has resulted in an increased mix of sales from international customers from 5% to 40% for Communications Systems.
Gross profit was $9.5 million, or 32.3% of revenue, compared to $8.9 million, or 30.0% of revenue, for the same quarter a year ago, an increase of 230 basis points primarily attributable to a higher mix of Communications Systems sales. Battery & Energy Products' gross margin was 27.0%, compared to 29.1% last year, a 210 basis point decrease due to lower sales volumes partially offset by improved 9-volt margins. Communications Systems' gross margin was 41.9%, an increase of 790 basis points over the 34.0% gross margin reported last year, which resulted from higher volumes and favorable sales mix.
Operating expenses were $7.1 million, compared to $7.1 million a year ago, reflecting lower discretionary spending and headcount reductions completed in the first half of 2012 offset by increases in selling and new product development expenses. Included in the 2012 operating expenses is a $200,000 charge related to the non-renewal of the company's U.K. lease described above. As a percent of revenue, operating expenses were 24.3%, compared to 24.0% a year ago.