iNum is the international initiative taken by Voxbone in order to create a geographically independent numbering plan with SIP call routing (+883 5100 prefix). At the moment only few carriers route those numbers directly. The iNum numbers are also reachable from Skype at a small per-minute charge.
If you have your own IP PBX, routing calls to iNum numbers is plain easy.
Also you can easily receive iNum calls on your PBX. There are a number of VoIP providers who offer iNum numbers free of charge. I registered mine at SIP Global Phone. It allows you to add an iNum DID number to your account and forward it to your SIP URI, for example:
|SIPfirstname.lastname@example.org||883510009024059||Active||Priority : 1||01:15||iNUM||Pending|
I don’t know what pending validation means, hopefully it’s not too harmful 🙂
As a result, you can reach your PBX at any of iNum access numbers around the world at local call rate. After dialing, you don’t get any prompt, and go ahead with dialing iNum digits. Hint: you don’t need to dial the whole iNum number, and the prefix 883510 can be skipped. So, for my number you would dial 009024059 (you will hear a short greeting and MOH from my conference bridge).
UPD: it appears that SIP Global Phone allows only a single call at a time, so it’s not usable for conferences. The rest works fine.