Summary: The Tracker DTS from Backcountry Access (BCA) was a very popular beacon. It set the standard as the first two-antenna transceiver in 1997. However, it has one the shortest ranges of the digital beacons and many of the newer digital beacons have easier to use controls. The Tracker2 and Tracker3 have many improvements over the Tracker DTS.
(Note that BCA increased the recommended search strip width of the Tracker DTS, from 20 meters to 40 meters, during 2010. The 2010/11 Tracker DTS user manual mentions both 20 and 40 meters, but the manufacture has informed me that they now consider the recommended width to be 40 meters. I'd stay closer to 20 meters.)
Searching: Intuitive blinking lights indicate the direction and the DTS senses changes in direction quickly. If you get off-course by a few degrees, the lights promptly indicate the new direction.
The fine search can be a little confusing, because the directional indicators (lights) continue to point (often away from the victim) no matter how close you are to the victim. To compensate for this, ignore the directional lights and use the distance numbers when you are within 2 or 3 meters of the victim.
Multiple Burials: The Tracker DTS and the Tracker2 have a "special mode" button that narrows the reception "arc" to 70° in front and behind you. The concept is that after locating the first transceiver you can press the special mode button to narrow the arc and only search for signals in front and behind the transceiver.
The special mode definitely requires practice. Your time will be better spent mastering the generic multiple burial search techniques rather than learning how to use the conceptually-complex special mode.
Controls: Turning the DTS on is obvious. Changing to search mode is easy, but not intuitive (you press the large red button until the letters "SE" are displayed at which point you release the button). The yellow "special mode" button narrows the range to help find multiple victims (many users tell me they thought it was used to mark a victim during a multiple burial). If you turn the unit on while pressing the yellow button, the Tracker DTS will automatically switch from receive to transmit mode if it doesn't receive a signal in a few minutes.