Features:
Dual-Optical Design- Reflectorless measuring requires a finely focused beam for pinpoint accuracy. Prisms need a wider pattern to prevent off-center measuring degradation. Topcon’s dual-optical system gives you both for the maximum measuring accuracy all the time.
Precise Pulse-Laser Reflectorless- Topcon’s pulse-laser “ time-of-flight” system eliminates measuring errors caused by the overlapping signals used in phase measuring systems. Accurately measuring corners or through objects such as a chainlink fence is always fast and reliable.
Longest Reflectorless Range- Up to 350m, the longest reflectorless range in its class! Measures up to 1200m with the 3000LW. The dualoptical design allows you the extended range using a class 1 laser- safe for all conditions making it ideal for use in high-traffic and other heavily populated areas.
Product Brochure & Specifications (pdf) 
Topcon’s GPT-3100W uses a dual laser optics system, one narrow beam for non-prism functions, and a broader beam when using a prism. This stabilizes the beam over long distances providing accurate measurement, even in adverse atmospheric conditions such as heat shimmer.
The most important part of the measurement beam is its unique “pulse” technology. A pulse beam emits timed flashes of laser light. These flashes (or pulses) allow the laser to discern objects that may be close to the path of the point you are shooting. Now reliably shooting building corners, or an object through a chain link fence, is as easy as point and measure.