Teledyne Technologies Inc. had a 74 percent drop in net income for the second quarter when compared to the same period a year ago. The Thousand Oaks-based electronics and engineering services firm reported net income of $39.5 million, or $1.06 per diluted share, on revenue of $518.5 million for the quarter ending July 1. For the same period in 2011, the company reported net income of $152.3 million, or $4.08 per diluted share, on revenue of $502.9 million. In 2011, the company recorded a $113.8 million gain on the sale of its piston engines business in its earnings for the second quarter 2011. Minus that gain, second quarter 2012 net income would have been similar to that of the same period last year. Teledyne is made up of four business divisions. The digital imaging business showed the highest gain in sales for the second quarter, increasing by 15 percent to $110.9 million from the $96.2 million in the second quarter 2011. The instrumentation business had a 6 percent increase to $162.4 million in sales from the $152.7 million in the second quarter 2011. The aerospace and defense electronics and engineered systems had decreases in sales in the second quarter compared with the same period in the prior year. During the quarter, Teledyne acquired a majority stake in Optech Inc., a laser-based survey and digital imaging instruments manufacturer; and announced its acquisition of BlueView Technologies Inc., a provider of acoustic imaging and measurement products. Mark R. Madler