This is a basic explanation on how to set up VoIP at home because there are a number of different configurations possible using a variety of kit. First, I need to explain some terminology:

• PSTN - Public Switched Telephone System. This is the ordinary public telephone system.
• DECT. This is the technology behind the wireless telephones that are in common use within homes. It consists of a base station that connects to the PSTN and one or more DECT phones that are registered with that base station.
• FXS. This is the name for the telephone socket on a piece of kit into which you plug a handset, a DECT base station, a fax machine and so on.
• FXO. This is the name for the telephone socket on a piece of kit that connects to the telephone provider’s socket. In other words, if you want some kit to connect to an existing PSTN line then you need one of these in it.

VoIP provider

There are two things you need to make this work:

As well as an ADSL (broadband) or cable Internet connection, you also need a VoIP provider in order to make this work. That is a company who will route your VoIP calls for you and provide interconnection to the PSTN for both incoming and outgoing calls.

VoIP providers come in three flavours:

1. Closed network using proprietary technology. Such as Skype. You can connect to the PSTN through them but not directly to other VoIP providers.
2. Closed network using open standards. Such as Vonage. They use industry standard technology like SIP so you can use different software and hardware to connect to them. But again you can connect to the PSTN through them but not directly to other VoIP providers.
3. Open(ish) network using open standards. Such as Sipgate or Gradwell. Through them you can also call subscribers to other VoIP networks and the calls are free of charge.

Option 1 - Existing phone with only a VoIP provider

This is the configuration that many manufacturers assume we want to use, though I doubt that many of us actually do. It works by adding a VoIP adapter in between your existing PSTN phone and your broadband modem. All calls then go out to your VoIP provider over your broadband connection. If you want access to the PSTN (incoming or outgoing) then your VoIP provider does that.

However you normally cannot do 999 calls or can you reach premium rate services. There are also limitations on whether or not you can move your existing telephone to a VoIP provider.
The setup looks like this:

Option 2 - Existing phone with VoIP adapter and retaining PSTN line

It is perfectly possible to retain your existing PSTN line and use just one phone to access both lines, you just need a VoIP adapter that also has an FXO port to plug into the PSTN socket. This gives you the best of both worlds.

The only real problem with this setup is choosing what calls go down what line. Some of the adapters are very basic in the functionality they provide. Another tip is to make sure any VoIP adapter you buy has a PSTN failsafe or similar. This ensures that you can get to the PSTN through the adapter even if the power to it fails.

This setup looks like this:

If you have a DECT phone then the setup will look much the same:

Of course you may be unlucky enough to have your PSTN socket and your ADSL modem in different rooms, in which case some VoIP adapters can use a WiFi dongle to access the ADSL modem. I only know of one, which is the Linksys WPB54G. This setup looks like this:

Option 3 - New hybrid DECT phone retaining existing PSTN line

You may wish to throw caution to the wind and buy a completely new phone system that does both PSTN and VoIP. One such example is the Siemens Gigaset C460IP (called the C450IP on Siemens website, C460IP is the UK-specific model) which is also a DECT phone.

This setup does not require and adapter since the DECT base station has that functionality built-in. It looks like this:

Option 4 - New WiFi phone with only a VoIP provider

Finally we come full circle to the most Internet way of doing things that uses the least amount of kit. This is using a WiFi telephone that connects directly with your WiFi ADSL modem and on to your VoIP provider. As mentioned above, there are potentially some issues with relying solely on a VoIP provider.

This setup looks like this:

That’s all for this post but we hope to have some future posts that review VoIP adapters and a few Hybrid or WiFi phones.