Our VOIP PBX server is designed to operate over any existing IP network , the following drawing describes a typical network setup for an office with VOIP PBX connected to local PSTN network (land line) and internation VOIP gateway for making cheap international calls , serving several extensions (VOIP handsets)
In the above example , calls can be made between extensions for free , and since the PBX is connected to a PSTN (land line) , our extensions can make domestic calls at local rates. On the right side we have a link to external VOIP gateway on the internet, VOIP gateways allow us to make internation calls at very cheap rates , sometimes costs less than local calls !
In our example , the PBX is configured to route all internation calls to external VOIP gateway.