Okay but seriously how does fax-over-IP work? I know you’ve got T.38 and G.711 options, those being a sort of internet-native fax and talking-directly-to-the-modem mode respectively. And you’ve got T.37, fax-over-email, which I strongly suspect won’t work.
But when it comes down to it, I have no idea how to turn a PDF into a fax without going via some service that provides a virtual printer device or a web portal. My VoIP provider says they charge 40p per fax, what are they actually doing for me? Are they simply charging for the UI? If I run my own PBX, are they encapsulating my fax in T.38 on my behalf, or do I do that? Are they charging me for a T.38 data stream going past them? Are they unencapsulating T.38 and putting it on the PSTN? What if I use G.711? Do they detect that and assume a fax?
Basically, I understand what a lot of the component blocks do, down to how SIP and SDP work, what group3 and group4 encoding is, all of that. What I don’t understand is whether I can set up a PBX or other software that is capable of sending/receiving fax and how it interacts with my provider’s billing.
