IIRC, Sprint DirectConnect works through the Sprint network using CDMA. Note that Sprint's DirectConnect is not to be confused with the 900MHz FHSS off-network Direct Talk capability that some NEXTEL phones had a few years ago.
I have 2 Sprint phones with DirectConnect. The DC function works slightly better than NEXTEL's DirectConnect did back in the day. Sprint's coverage is better too but relies heavily on Verizon for roaming and the DC function works there too. The phones sometimes get confused when going from a Sprint network to roaming on a Verizon network and causes the DC function to stop working even when both phones have service. Other times it works seamlessly. Power cycling the phone usually fixes it. Sprint's DC appears to have a few quirks but it seems to work a little better than NEXTEL's DC ever did.
Good luck.
I also have a Sprint Direct Connect handset, and i did some playing around with it when i was up north (NW WI, a Verizon roamming area), and i had no problems with it figuring out what towers it was `sposed to be on, if it did as you said i just power cycled my unit and all was well again
. I had the Nextel units too, and i also find that Sprint`s coverage is better (i can use my handset up north, which i couldn`t with my Nextel phone unfortunately), and honestly i like the audio better from the Sprint DC too, Nextel was good for a noisy environment, but get it in a quiet one and it could get painfully loud, usually turning down the volume fixed THAT issue
. N9NRA.