ProVu Communications - Voice Over IP Solutions for SME

VoIP Solutions for SME

This document is a Voice over IP primer for SME customers who want to understand the benefits of using the technology in their business.


SIP is the protocol that binds most VoIP systems together. There are other protocols, but SIP offers an open standards solution. This means that services and equipment purchased from different vendors can all work together successfully.

Most VoIP systems will provide SIP account details for you to put into your SIP phones.

What is Possible

A distributed phone system. Features include:

  • Call Transfer
  • Voicemail
  • Direct Dial Numbers
  • Unmetered Calls over IP
  • Hunt Groups

Using Business Class Handsets can bring features that are unusual in SME systems:

  • Caller ID Display
  • Call Waiting

On-Site or Service Provider

You can setup a VoIP system by setting up the servers and gateways yourself, connected to your own phone lines and Internet connection.

Alternatively you can use a SIP Service provider or ITSP (Internet Telephony Service Provider) to do it for you.


This is sometimes called IPBX (Internet PBX).

Advantage: Keep your existing phone numbers. Internally the system will operate without your internet connection.

Disadvantage: Upfront cost of servers, software and gateways.


  • SIP Proxy Server - Registration, Authentication
  • SIP Media Server - Voice mail, Music on Hold
  • PSTN/ISDN Gateways - Your Link to Normal Phone Lines
  • SIP Phones

Alternatively something like Asterisk includes the server components (Media, Gateway and SIP) all together.

Service Providers

If you use a SIP service provider, you don't have to setup, maintain or pay for your IPBX setup.

You can add features and services to your system by paying your service provider. To add more extensions you just need to buy more phones.

Although you rely on your internet connection - if it fails then all of your phones go offline

Service Providers to Try

These providers are listed without any recommendation, but reference to see what services are offered.