Hi aabs, The
SD49225XA-HNR comes "standard" now without Auto tracking feature as Dahua removed this feature because they are greedy
censored and want you to buy more expensive models such as 5 or 6 series.
SD49225XA-HNR and SD49225T-HN-S2 the difference is the 225T is the old model not Ai and no PFA and sucks@ auto tracking.
Dahua do have a "secret custom firmware" which is not available to download.
There are a few sellers who will load this firmware on the camera for you ONLY if you buy the camera from them but they will not send you the firmware if you buy the camera elsewhere.
I have this "Secret Dahua Firmware "which I have sent it to many forum members here who have re enabled auto tracking on their camera's without any problems.
I am not a trader or seller and don't make any profit from here or anywhere else I just like to help people this matters to me more than money. If you want to buy this camera from where ever and it comes without auto tracking send me a PM and I will send you the "Secret Dahua Firmware"
Regards Andy
PS: Remember anything you buy from China has Zero UK Warranty and if anything went pear shaped with it you can imagine the ball ache you will have.