Frequently Asked Questions

VoIP (Voice over IP) is littered with terms and concepts that might lead to confusion and misunderstanding. There are some key concepts which need to be understood to make informed decisions when considering a new business telephony system.

VoIP, Voice over Internet Protocol - This is an umbrella term for any form of voice communications where voice is carried over any IP network (i.e. a network computers use to talk to each other).  Most commonly, the IP network is your internal office data network.  However, as the internet is an IP network, VoIP traffic can be carried over the internet too.  It is key to understand how voice traffic can be carried to and from business premises and within business premises.

PBX/PABX – This is a telecoms term referring to a Private Branch Exchange or Private Automatic Branch Exchange (same thing), i.e. the system which allows lots of extensions to be connected together & controlled within business premises.  PBXs have evolved rapidly over the last few years into specialist computer systems where the software contains delivers the telephony intelligence rather than specifically designed telecoms hardware.  Given suitable connectivity, VoIP PBXs can deliver free calls between business sites.

ISDN – Traditional business telecoms lines rented from a telecoms firm & allowing voice to be carried to & from your premises.  ISDN comes in 2 flavours – individual ISDN2e lines each of which allows 2 simultaneous calls or ISDN30e which has the line capability of handling up to 30 simultaneous calls though you only pay for the number of lines you actually want (minimum for ISDN30e is 8).

SIP/IAX/VoIP trunks – These are the VoIP equivalents of ISDN.  They use your broadband connection to make calls at reduced costs over traditional lines. They can be used in conjunction with an VoIP PBX to deliver the best of both worlds – for example, high quality calls & reliability of traditional telecoms for every day use while using VoIP trunks to save on international call charges.

Hosted VoIP/IP PBX – This is where the PBX system is held externally by a third party & your broadband connection carries voice traffic alongside data traffic, and the PBX functionality (e.g. voicemail).  The same PBX will handle multiple clients.

21CN – BT’s project to convert the whole of it’s UK network to use VoIP technology to carry voice traffic.  This project is happening now with scheduled completion in 2011.  Not all existing PBX technology will be compliant with this new network.