VoIP (Voice over IP)

The emergence of Voice over Internet Protocol (VoIP) changed the telecom sector forever and has become integral to how we communicate with one another. But what exactly is VoIP, how does it work, and why is it so important these days?

What is a VoIP phone system and how does it work?

VoIP refers to the method of transmitting voice over the internet, rather than via a regular landline or a mobile network. It is generally considered the main alternative to the traditional phone system: the Public Switched Telephone Network (PSTN).

That said, the lines blur between the two more by the day now that digital platforms such as Microsoft Teams can be connected to the PSTN. This is achieved using integration technology like SIP Trunks and an IP-enabled PBX (Private Branch Exchange), which is simply a private telephone network used within an organisation.

How does VoIP work?

Making a phone call using VoIP is similar to doing so through the PSTN, but it occurs via an internet connection instead of old copper wires and telephone lines. A VoIP service converts an individual’s voice from audio signals to digital data that’s sent through the internet. If calling a traditional phone number, this audio is instead converted to a telephone signal before reaching the other caller.

The process of sending data involves encapsulating the audio into data packets, transmitting them across an IP network, and then converting these packets back into audio at the other end.

Direct Routing for Microsoft Teams
Why Is PSTN Calling Important?

What are the main features of a VoIP phone system?

Some of the main features of a VoIP phone system include:

  • An IP-enabled telephony system to manage user telephone numbers, devices and features.
  • Gateways to connect networks.
  • Session Border Controllers (SBCs) effectively convert VoIP to the PSTN. They do this by converting IP packets to voice signals (and vice-versa) which are transmitted onto the PSTN.

What are the benefits of VoIP?

Among the main advantages of VoIP telephone systems are:

  • Low costs - VoIP is typically cheaper than standard phone calls, with no international rates either.
  • Extra features -  Most VoIP telephone systems come with added features like call recording, call reporting and custom caller ID.
  • Access for remote workers - VoIP gives remote workers more choice when connecting to meetings.

VoIP as part of unified communication for your business

Because VoIP works in conjunction with other types of online communication (like voice, video, instant messaging, voicemail, and content sharing), it can help deliver unified communications. This is where multiple communications technologies are integrated into one platform, which has many benefits, including:

  • Greater productivity.
  • Organisational agility.
  • Cheaper infrastructures.
  • Better user experience.
  • Streamlined operations.
  • Easier integration with existing business systems such as CRM.
  • Easier access for remote teams.

As we explore below, Microsoft Teams is one of the best VoIP-enabled platform to facilitate this.

What are the benefits of using Teams for VoIP calls?

Although there are many VoIP-enabled platforms you can use for business collaboration (including external calling), our research shows that Microsoft Teams is very widely deployed and is also the pick of the bunch. This is because Teams calling offers:

A Single Point Of Contact

A single access point.

Place External Calls Within Teams

Full PBX capabilities.

Telephony Heritage and Hybrid PBX Capability

Seamless integration with Office 365.

Centralisation Of Data

Centralisation of data such as communication history and contacts.

Callroute can also support you with VoIP calling for other platforms, such as Cisco Webex and Genesys Cloud CX, as well as the integration of existing legacy equipment such as PBX's using the Callroute SIP Trunk integration solution.

VoIP and Microsoft Teams Integration

There are two main ways to make a VoIP call using Microsoft Teams:

Teams-To-Teams Calling

Teams-to-Teams call

You can use Teams to call any other internal Teams users, though there are certain drawbacks to this. For example, external communications can be difficult as other individuals may not have Teams installed, while there is limited analytics and call management functionality. This potentially reduces the effectiveness and affordability of this communication method.

Call using another app

Apps such Cisco Jabber, Webex, RingCentral and Zoom can all be used in tandem with Teams to make internal and external calls. Overall though, this doesn’t create a seamless, centralised and properly integrated experience, as users will be forced to switch between apps.

Why You Should Integrate Microsoft Teams With Your Telephony System

Why you should integrate Microsoft Teams with your telephony system

As explained on our PSTN page, you’re better off integrating Teams with your company’s PSTN telephony system so you can use the platform to place standard phone calls to landlines or mobiles. 

How to set up PSTN calls with Microsoft Teams

Although you can utilise Microsoft Phone System and its Calling Plans to set up PSTN calling with Teams, this has notable issues. For instance, it doesn’t offer features like call recording, reporting or extensive call queue management capabilities, which will make it difficult to dispense with your traditional telephony system.

Instead, we recommend a Direct Routing solution via a third party provider to integrate Teams with your PSTN system. This provides you with a fully-functional business telephony system that immediately improves Microsoft Teams, giving you total PBX integration (including control tools like reporting, call recording and queue management), and endpoint and handset flexibility.

Callroute’s Direct Routing solution

At Callroute we offer a solution which delivers  Direct Routing in minutes using autoconfigured integration processes. This reduces setup time significantly compared to other providers. 

All in all, our tool enables users to replace their phone system with Teams and maximise business collaboration, offering many benefits over Microsoft’s Calling Plans. It enables you to properly unify your communications, with a free line for life, flexible per-channel pricing, the ability to buy new numbers, plus a number porting service and 24/7 on-demand support.

In addition, as a company in the corporate telephony sphere, we understand better than most why having reporting, security and calling features is so crucial. With our Direct Routing solution, you can choose caller IDs, monitor call history, track user activity, see call statuses (including location, duration and whether calls are outbound or inbound), enable remote access to your phone system, and more.

Get in contact if you’d like to try our solution or find out more about how we can help your business.


In order to make VoIP calls you need:

  • A reliable internet connection.
  • Either a landline phone (which requires a VoIP adapter), a laptop/desktop computer, or a smartphone.
  • Your chosen software installed.

The licenses you need for VoIP calls with Teams depends on the version of Office 365 you have. Please visit our Prerequisites page to find out your own company’s requirements.

To make VoIP calls to PSTN users, in addition to the VoIP call prerequisites, you will also need a subscription to a cloud telephony provider such as Callroute.

How much VoIP costs depends on your set up. Although app-to-app VoIP calling is usually free, ringing a landline or mobile number can come at a cost, while other VoIP services charge a monthly fee.

Most internet providers require you to have line rental in order to receive broadband, so you may have to keep it. If not, you might be able to do without your landline if you make very few calls. But as we touch upon in the next section, this probably isn’t the best idea.

Understand External Calling with Microsoft Teams

Check out our modern telephony page to learn more about modern telephony systems, including the role of things like Session Initiation Protocols (SIPs) and Session Border Controllers (SBCs), and the benefits of integrating different systems.