I can't do anything about the downvotes but I've messed around with the theory behind this and have a few observations.
I've done an edit that should have it in better shape, but I think this is one of those 'unfortunate' intersections of vaguely obscure technology and well, people.
I'd say its on topic, but most people don't know VOIP lingo (I can't find a good wikipedia page explaining FXO) - what you need might actually be something else entirely.
While its not off topic for us - I suspect a space that's more specific to people building VOIP systems and are familiar with the lingo and hardware might be better than quora.