Geoff Darst wrote a review of Ortovox M2 Avalanche Beacon on January 26, 2004
Distance and signal strength information makes locating the victim simple. Plus the display tells you when to change your distance attenuation. IMO the M2 is just as easy to use as a Tracker. In practice I found the short range of a Tracker to be limited to slightly less than 40m, while I was getting 80m out of the M2. Does range matter? All I know is I want a signal sooner rather than later. I also found the M2 to be superior in fine-grain searches. The audio tone of the M2 changed noticeably when you were right over the victim while with the Tracker you never know until you probe. The M2 is also much better for multiple burials. You can hear the other beacons and you can adjust the range attenuation to quickly identify the relative distances from the initial beacon.