The next step up from a standalone Voice over IP (VoIP) phone is your own, in-house switchboard (PBX), able to support multiple extensions, handle voicemail, route incoming calls and so on. Hardware solutions can be expensive but there are alternatives, such as the 3CX Phone System for Windows which can be downloaded for free. All you have to supply is a PC to run it on.

There's no need for any special hardware, just an ordinary Windows PC, even a virtual machine if preferred. Installation took just a few minutes on our test system with no problems getting it all working even though the components, including an Apache Web server and PostgreSQL database server, are far from standard, at least as far as Windows is concerned.

And that's down to the browser-based management console, which comes with wizards and templates to help get the product up and running, plus an intuitive interface for day-to-day administration.

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The initial setup wizard starts out by asking about the extensions you want to configure, after which it's down to you to install the actual handsets or PC softphones. Any SIP (Session Initiation Protocol) phone can be used, as can SIP adapters to convert ordinary analogue/digital handsets for use with VoIP. On the downside these can be difficult to configure, so 3CX offers detailed instructions to help setup the most popular products from leading vendors such as Grandstream, Linksys and Snom.

SIP softphones, such as X-Lite, can also be used, with a free 3CX softphone bundled as part of the package.

Having configured the extensions, users can call each other via the PBX, forward and transfer calls and so on. Changing or deleting users is child's play and hot-desking a standard feature, with users able to logon from any handset or softphone with a PIN code for authentication, even when teleworking from home or another office.

The next step is to connect the PBX to the public switched telephone network (PSTN). This takes a little longer and, unlike some alternative products, the 3CX software doesn't include a PSTN gateway of its own, relying instead on third-party gateways. Typically implemented as standalone appliances, these can be had with either ordinary phone or ISDN interfaces, with templates for use with products from vendors such as Mediatrix, Linksys and others, again, to help ease any setup issues.

Another option is to simply connect the PBX to the outside world via an Internet connection and hosted SIP services rather than dedicated phone lines. Pre-configured templates for use with popular services, again, make this easy to do, with support for generic SIP trunks and DID (Direct Inward Dialling) also available.

We tested the free download, but three commercial versions are also available. All support an unlimited number of extensions, with the free version limited to eight simultaneous calls as is the Small Business edition (from £268 + VAT).

Up to 16 simultaneous calls are supported on the Pro version (£568 + VAT) and 32, upgradeable to 128, with the Enterprise edition, starting at £821 + VAT. The commercial versions also come with bundled support plus additional functionality such as call recording, Exchange integration and the ability for users to manage their own setup via a Web portal.

Regardless of the edition involved, much of what you want in a small business PBX is delivered by the 3CX software. We found it easy to configure and were impressed by the built-in features, with support for hunt groups, music on hold and so on, all as standard.

Voicemail, complete with e-mail notification, is another useful feature, along with Outlook integration and a fax server. An integrated Digital Receptionist ("Press button 1 for sales", etc.) facility, is also bundled, although some technical knowledge is assumed throughout and small business users may need to buy in specialist help to get started.

A surprisingly easy to manage alternative to hardware-based IP telephony products, all you need to install and run the 3CX Phone System for Windows is a PC. The end result is a fully featured in-house PBX, offering support for as many SIP-enabled handsets as you like plus voicemail, PSTN connectivity, automated call handling and a whole lot more.