PBX to PBX
A single PBX can handle many extensions and connections. The only limiting factor is the total bandwidth used to connect the extensions to the PBX.
To allow a more diverse VOIP system, groups of extensions are connected to their own PBX, eg all extensions within the 0191 area, all extensions within the 01642 area.
If extension 0191ext1 wants to talk to extension 01642ext2, the direct dial number would be 01642ext1 and within the NEDNET-PBX, the OUTBOUND ROUTE dial pattern knows to route the call to NEDNET-PBX1.
As the system expands, more PBX's would be utilised to cover a specific AreaCode and located within the mesh area.