Carl, is right. The DIS-300 is a thermometer. The laser beam(s) merely show you the spot you are pointing at.
Although it was not designed for Treasure hunting, It is handy in locating cold spots in the terrain where large changes in the average ground temperature, may indicate a cave or tunnel entrance.
The DFS V.10 is a Frequency Discriminator. Although it utilizes hand held rods that might could be used for Dowsing, no mental effect is used. Target Discrimination is accompolished with electronic Frequency, unlike Dowsing where target Discrimination is done through a mental process.
There is information about my use of Frequency Discrimination Devices and some of it's limitations posted on my product website
http://www.omnitron.net
Be cautious of exaggerated advertising claims that promote advanced LRL technology. It may sound good, but if you purchase with having unrealistic expectations of the product, you will be subject to disappointment after you buy. Be a well informed consumer before you decide to buy. Dell