IT Pro is supported by its audience. When you purchase through links on our site, we may earn an affiliate commission. Learn more

The business buyer's guide to VoIP

Traditional phone services are being discontinued. It's time to switch to VoIP - or perhaps to upgrade your existing PBX system


The saying 'If it ain't broke, don't fix it' is a worthy rule of thumb - but if you're too resistant to change, you can end up hanging on to outdated technologies for far longer than it's sensible to.

So it is with PSTN and ISDN telephone systems, which many companies still rely on for their critical communications, even though they've long been superseded by VoIP technology. Indeed, VoIP is so mature that if you already have an IP-based system in place, it's probably time to re-evaluate your options.

If you need a killer reason to switch to VoIP, the big one is cost. Compared to traditional landlines, VoIP offers huge savings in call costs, especially for international calls. For most businesses that will be a persuasive argument on its own, but there's more; VoIP is simple to configure - so you can set up new starters or enable hot desking with just a few clicks - and the option of cloud hosting means it can be terrifically simple to install too.

It also supports professional features such as digital receptionists, call management and forwarding and voicemail and IVR (interactive voice response) services, which can create a positive impression of your business.

Indeed, you're going to have to embrace VoIP before long anyway. BT warned us some time ago of its intention to switch off its PSTN and ISDN networks and migrate all existing customers to IP networks by 2025 - and it won't be offering new PSTN and ISDN services from 2020. The switch is coming; the only question is how and when you embrace it.

But don't be daunted. There's a diverse and ever-growing range of VoIP services on the market, so you can be confident of finding one that suits your needs.

Broadband questions

Switching to VoIP requires little in the way of infrastructure, but you do need to make sure your internet connection can handle the traffic. VoIP is very sensitive to network conditions, and an overloaded connection is likely to lead to garbled, stuttery calls - which is hardly the professional image you want to project to customers. If you're not sure whether your connection is fast enough, you can test it using free online tools, such as those at

Use an online speed test to check your broadband connection can handle voice traffic

If your connection isn't fast enough, you'll need to upgrade to a faster link, or get a second line dedicated to VoIP traffic. If you're running your own onsite IP PBX, you may also need to configure your firewall to allow external users to access VoIP services. Look for QoS (quality of service) settings too: these allow your router to identify voice traffic and prioritise it over data, to keep things clear and smooth.

Keep on trunking

The basic requirement for any VoIP system is a SIP (session initiation protocol) trunk, which connects your PBX to the public phone network.

There's no shortage of operators who'll provide this service; the price will depend on how many channels you need - that is, how many simultaneous VoIP calls you want to support.

For testing, we use SIP trunk services provided by VoIP Unlimited

For moderate IP phone usage, one SIP channel for every three users is a decent starting point, but it's a good idea to monitor how your staff use their phones during busy times to get a clearer idea of the number required. No matter many channels you have, you can set up as many extensions as you like, and make unlimited internal calls.

To test our VoIP systems, we use the SIP trunk service provided by VoIP Unlimited. There are plenty of alternatives, but we particularly like its web portal, which provides trunk status, call statistics, diagnostics and the option to block calls to premium-rate and international numbers.

When choosing your own provider, look for one that will port your existing phone numbers across to the trunk. Some will charge for this service, but it's worth doing - this way, you won't have to advise customers of new numbers or reprint business cards and marketing materials.

Onsite or cloud-hosted?

Running your own IP PBX is cheaper than using a cloud provider, and it gives you total control over your VoIP services. You can purchase preconfigured hardware appliances, or install the back-end software on a server you already own.

Don't skimp on the hardware, though. An IP PBX uses a lot of TCP/UDP ports and can be quite resource hungry. We suggest you avoid running your PBX on a server that's already handling other duties: you don't want to risk conflicts with other applications on the same host, which can be difficult to diagnose and fix.

For smaller businesses that don't have the on-site expertise to configure and manage an on-site IP PBX, there's nothing wrong with cloud-hosted solutions. The price is higher, but the market is competitive, with plenty of providers to choose from, and lots of convenient packages that include preconfigured SIP trunks, channels and call routing features.

Management is easy too: normally, there's a web portal that lets you keep an eye on your VoIP services no matter where you are. Cloud hosting also means remote workers can access VoIP services even if the main office is offline or otherwise inaccessible.

Softly, softly

VoIP doesn't just mean cheaper calls - it can also cut costs by eliminating the need for physical phones. Many providers, including 3CX and RingCentral, offer softphone apps for Windows, Mac, iOS and Android devices, which can be used with lightweight headsets. There are plenty of these to choose from, and you may be able to get discounts if you buy them from your VoIP provider.

3CX speeds up iOS softphone registration by providing a QR code in the user's web portal

Alternatively, if you prefer desktop handsets, there's a good range of IP-compatible models out there too.

We often use Yealink T23G IP phones in our tests, which are easy to provision and have great hands-free operations, but again you have plenty of options; other vendors such as Snom, Polycom and Grandstream all offer affordable and feature-rich handsets.

VoIP really is an easy win for small businesses, allowing them to reap the benefits of cheap local and international calls, easy scalability and professional call handling features - and it's perfectly poised for the next generation of mobile workers.

Image: Shutterstock

Featured Resources

Four strategies for building a hybrid workplace that works

All indications are that the future of work is hybrid, if it's not here already

Free webinar

The digital marketer’s guide to contextual insights and trends

How to use contextual intelligence to uncover new insights and inform strategies

Free Download

Ransomware and Microsoft 365 for business

What you need to know about reducing ransomware risk

Free Download

Building a modern strategy for analytics and machine learning success

Turning into business value

Free Download


What does a CISO do?
Careers & training

What does a CISO do?

12 May 2022
Business value on AWS

Business value on AWS

27 Apr 2022
How to delete a Facebook business page
social media

How to delete a Facebook business page

11 Apr 2022
What is Business Intelligence (BI)?
business intelligence (BI)

What is Business Intelligence (BI)?

3 Mar 2022

Most Popular

Russian hackers declare war on 10 countries after failed Eurovision DDoS attack

Russian hackers declare war on 10 countries after failed Eurovision DDoS attack

16 May 2022
16 ways to speed up your laptop

16 ways to speed up your laptop

13 May 2022
Google Russia files for bankruptcy, ends operations in the country
Business operations

Google Russia files for bankruptcy, ends operations in the country

19 May 2022