what's the difference between a 7610 and a 7610B? i know they have different firmware but that's all i know.
what's a 7610B
I could be mistaken, but I think it is the exact same hardware, but with a Cingular Wireless (U.S. operator/carrier) firmware version.
What's different in it I don't know. Probably things like their WAP/GPRS/MMS settings, browser homepage, links & such, possibly some apps of their own they want on it, maybe removed things they might not have services for - likely candidates would be Chat & Presence, for example. That is, the "usual" kind of stuff that operators/carriers tend to want in phones they resell (with or without contracts/subscriptions/plans/whatever-you-want-to-call-them).
after some searching i found out that a 7610b runs 850(800)/1800/1900Mhz and a 7610 runs 900/1800/1900Mhz
so what's the difference? ... in the US 850(800)Mhz is popular among AT&T and Cingular i believe. Although AT&T and Cingular have 1900Mhz towers, they would only be in their newer areas of service. T-Mobile runs 1900Mhz exclusively so looks like I'm going to T-Mobile w/ my phone. (i wanted to anyway)
I hope this helps someone.