In reply to:
Gradwell (at al) provide the virtual PBX. The end user needs three phones that are either IP Telephones (plugged into ethernet) or ATAs that allow a standard phone to connect to VoIP via ethernet. Each phone will be an extension off the virtual PBX and the incoming calls can ring a group, hunt, or whatever strategy they need.
I have found this service from another provider (voipfone) but Gradwell's "Centrex" product appears to offer
some of the benefits of Virtual PBX but you are limited to two simultaneous calls on each telephone number - although it does allow several extensions access to those two lines.
To quote the sales rep's e-mail:
"You need 2 numbers from us in order to have upto 4 simultaneous calls these cost �4.99 each to setup and �7 per mth to rent. If you require more calls you simply add extra numbers albeit people need only dial the main number.
[rather confusing terminology there] With each number we supply 10 extension numbers which are used to address the devices making and receiving calls and setting up IVR menus, hunt groups etc"
The Voipfone service allows you to have up to 800 extensions to a single telephone number, all capable of calls at the same time, however you have to pay 99p for each extension rather than getting 10 extensions for �7. For 4 calls simultaneously with Gradwell it would cost �14 a month to rent plus a setup fee of �9.98. With Voipfone it would cost �3.96 a month to rent and no setup fee.
The Gradwell arrangement might scale-up well for a larger organisation as the ratio of lines to extensions can fall as the likelyhood of all the lines being engaged at the same time reduces. However this would need to be at a rate of 7 extensions per line before it matches the Voipfone arrangement for cheapness.
My friends business is never likely to need more than 4 extensions, and could make do with 3, one for each of the people who work there. The chances of all three of them being on the phone at once is actually quite high, their current single line is clearly not enough. The Voipfone system suits their setup better than the Gradwell one.