David, I have the AT-2004 . It has two transmitters, one for energized circuts and one for unenergized. It tracks underground feeders very well. Have even tied on to buried tv and phone lines to keep from trenching through. Used one for years that belong to a buddy that worked at the supply house. I bought mine this year and have been very pleased. (psss, don't tell anyone but I got mine on ebay... cheap!).
