This is a typical VoIP implementation that is suitable for most businesses.

For many Small Businesses, and for larger ones which are typically concentrated at one site, a more expansive implementation is to install your own VoIP Server, configured as needed. This is also the most configurable and customisable option. There are several different versions of PABX Software, some commercial and others are open-source, with the open-source often far more cost-effective (especially as some commercial versions still charge a fee per extension per month/year).

Virtually every feature is available, any type of connectivity, virtually an unlimited number of extensions and maximum capabilities are limited mostly by the processing capability of the server hardware.

Users located at other than the main site, can connect back to the server located at the main site and appear as simply another extension.

Another option is that the VoIP Server can be hosted external to the company premises, if there is no requirement to connect to the existing PSTN services.

Costs:

Initial setup costs include: Server hardware, connectivity hardware, telephones and initial labour charges for installation and configuration.

Again, ongoing costs are the PSTN line charges and any VoIP services, along with hosting charges if applicable.