The Topcon DT 209. Feature the same high-quality advanced absolute circle reading technology found in Topcon's high-performance total station products, and they continue to deliver the highest quality optics and electronics you expect to find in Topcon theodolites. All this, plus the addition of a laser diode that's perfect for easy, one-person alignment jobs. * Longer battery powering duration Longer battery powering durations using alkaline batteries. Continuous angle measurement for 150 hours (DT-213). Laser continuous angle measurement for 45 hours.