VoIP and the PSTN
Because not everyone uses VoIP, and because there is a mix of open standards and proprietary VoIP systems, at some point you need to connect into the PSTN. It can be thought of as a “last resort” type of connection, however it’s a vital way to communicate with someone who doesn’t have access to VoIP, or to allow them to communicate with you.
There are two basic solutions:
Firstly, if you have a VoIP capable PBX in your office, then the simplest solution would be to connect that PBX to the PSTN connections that you already have – analogue (POTS) or digital (ISDN) connectivity is possible. Then you can call your colleagues using the VoIP system, and when you need to call someone who is not contactable via VoIP, you fall-back to good old BT (or whoever you use to bring PSTN lines in!)
Secondly, you can use an external VoIP to PSTN gateway service. There are many companies in the UK (including ourselves!), who will provide you with a service from a simple single line to blocks of lines with full DDI services. These services can be used to expand and build on existing office PSTN connections (e.g. as your business grows, rather than have BT put in more phone lines, then you can have them provided via your Internet connection, into your VoIP capable PBX which may work out a lot cheaper) You may also want to consider this from day 1 on a brand new site, especially as you need a broadband connection, so might as well use it for telephony as well as data rather than run in a separate ISDN lines.
One thing to note: One of the big advantages of VoIP is that it’s free, or seen to be so. However, when using the PSTN you will almost always have to pay for it. BT, etc. do not provide their services for free! If you are using in-office PSTN connectivity, then you will already have bills, and so on from BT, so it may be worth your time checking them to see if BT have any offers which might give you cheaper calls. There are also other carriers who may be able to save you money on your regular PSTN calls, and look out for deals which offer a fixed-rate for “unlimited” calls. Do read the small-print though as there are often restrictions which make “unlimited” not quite as unlimited as you think it might be.
The same goes for the VoIP to PSTN termination services. Check their deals, check your bill, see what rates they have and how you can best apply them to your businesses needs.
