I replaced my old Dogtra T&B 2502 system with the new Dogtra T&B Dual system. I had the old 2502 for 7-8 years I am guessing. The new dual system is very similar to the old, with a couple nice exceptions. The new Dual system , first has separate controls for each training collar, no trying to manage toggling between the two collars. It seems a beefier in construction also. It has a pager on each collar, that allows user to page each collar without electric stimulation, which I really like, it get's the dogs attention without zapping them, lol. It also of course has the beeper settings for point, run, or locate, the latter is most often what I use. I purchased my system from Collar Clinic in Michigan, who i would recommend highly, I have used them several times in the past, and they are always very helpful and quick in their responces. I have only had system a week or so, but I am liking it.