Some websites you run into show you photos of SIP enabled IP telsets, but the interesting thing, is while it can run on top of an Asterisk for an example; a lot of times they are not. Many open source deployments claims on other sites are heresy, especially if not confirmed. I can say where I live many of these SIP phones go out on the Internet with no box on site. And it’s roaring in and it makes me concerned about small business more vulernable to VOIP than enterprises a decade ago.
Asterisk is dead for premise based systems. It would not be a stretch of one’s imagination that Asterisk would be used for SIP and other VOIP providers. Here is one example, your local cable company can provide this without any need of a PC on your end! And they give you the set on the spot! (Opps, I just dinged Comcast and expect a flood of solicitations again for Business Class – and boy was our mailbox so quiet from them for the last couple of weeks…) But the inherent problems is Asterisk’s scalability and the PC-first approach not App-first, meaning that the app (Asterisk) should be specific requirements, for 20 users, 100 users, 1000, 10s of thousands. But no, it’s very vague and “oh it’s up to you” attitude. As I said before, why would any business on their left side of their brain insist of taking an old PC to handle 20 users, when that is more costly than say going to the clouds.
So when you see a Polycom or an Aastra or something like that, you can assume without making italics out of yourself, that those phones are being tied to an ITSP or the Internet Telephony Service Provider. I would suspect this site using what if memory serves me an NEC Sphericall is a minority.