While Apple’s iPhone may have grabbed all the headlines lately, for many, Nokia’s N95 is much more interesting.

For starters, it has 3G capabilities, plus it’s based on the Symbian operating system, with a wealth of third-party applications available. Then there’s the built-in GPS and Wifi connectivity.

However, one of the really interesting applications is Voice over IP (VoIP) telephony, using standards-based Sip (Session Initiation Protocol). The phone networks aren’t keen on it – Vodafone and Orange have removed the functionality from the handsets they sell – but with a little careful work you can put it back again and find even more uses for the N95. And that’s precisely what we’re going to demonstrate in this article.

What’s so great about VoIP?
The N95 isn’t the first mobile phone to have VoIP functionality built in, or the first to have Wifi. And thanks to the Symbian operating system, you can add third-party VoIP software such as Truphone to other handsets quite easily.

What makes the N95 special is that its integrated VoIP capability works with everything else fairly seamlessly. You can use the same address book, so you don’t have to enter caller’s details into a separate VoIP application, and you can just look up a number and choose whether to make a mobile or internet call.

Thanks to Wifi and cheap VoIP deals, the savings could be huge, especially when overseas. So it’s no great surprise that the mobile networks aren’t encouraging VoIP. Not only do the conditions for internet access in many contracts now exclude voice and instant messaging over 3G, but they’d rather you don’t use VoIP over Wifi – lest you cut into their profits – which is presumably why some of them have removed the facility from the firmware they ship on their branded N95s.

VoIP at home
VoIP doesn’t have to mean using your N95 at public hotspots, though. Many people have a wireless network at home and cordless Dect phones. Convergence has been much talked about over the years, where you can use the same handset on your landline or as a mobile phone (using a mobile network or VoIP over Wifi) when you’re out and about. But the N95 can do all these functions.

The key to all this is Asterisk, the open-source PBX (private branch exchange) software. Originally designed for Linux, it now runs on a variety of platforms. For the sake of simplicity, we’re going to use the 32-bit Windows version from www.asteriskwin32.com, so we can run it in the background on an existing PC. On its own, Asterisk can work with Sip phones – products such as the Grandstream Budgetone range, for example – or with software phones such as X-Lite, or with the Sip software in the N95.

Asterisk can route calls between the phones, giving you internal extensions, and use your broadband connection to make calls via a range of VoIP providers. With a suitable voice modem or telephony card in your PC, it can also link to your existing landline.

Getting started
Asterisk looks pretty complicated at first, but there’s quite a lot of information available at www.asterisk.org/support. You’ll find a link to download a book published by O’Reilly, Asterisk: The Future of Telephony, free of charge. It’s well worth a read as it has a lot of useful information about the concepts that underlay Asterisk. You’ll also find it on this month’s cover disc.

If you have an N95 from Orange or Vodafone, you’ll also need to update it with firmware that has not had the VoIP functionality removed. If you don’t see the ‘Internet tel’ application when you select Tools from the menu, then you’ll need to do this. But note that while we didn’t have any problems, it’s possible for this to go wrong and you could end up with a phone that needs to be restored – at your cost.

You may invalidate your warranty, too, or your network may refuse to replace a phone if you’ve changed from its firmware to Nokia’s generic version, so we can’t accept any responsibility. You have been warned, so read the fine print of your contract very carefully. If you have a Sim-free model, this doesn’t apply, of course.

We can say, however, that many people have done the firmware update without problems. You’ll find details on how to do it, and how to configure the Sip settings, in our walkthrough.