Good morning, I have several optipoint 410 economy but without SIP firmware... I can't find any FW compatible in order to upgrade it to handle SIP accounts. Still, since it's a IP phone, is it possible to connect it to 3CX with any particular configuration? Has anyone tested it or has a compatible FW to make it work? I read something about particular models. These ones are S30817-S7212-A107-xx Thank you.