25 March 2019

Organising your business telephony can become very confusing. Terms such as SIP, VoIP, hosted, analogue, digital, KSU and so on, are used often, and sometimes interchangeably. So it’s no wonder that, after a bit of internet research, you’re still nowhere nearer finding out which business telephone system is right for your business than when you first started.

Therefore, this article is going to concisely explain the different types of business telephone systems available and help you find out which one is best suited for your business.

But, before we begin, we need to explain the following two points in order to avoid confusion:

  1. Telephone Systems and lines are two separate things

    A telephone line is a physical wire which connects the telephone to the network. These lines are used to deliver landline services for digital phone systems.

    A telephone system is the interconnection of several telephones, usually found in a business setting. Depending on how basic or advanced the telephone system is, it can allow for features such as call transferring, putting calls on hold and call logging.

  2. You may have heard of ‘hosted’ phone systems.

    This basically means that the physical phone system is located off-site. You can only have your phone system hosted if it runs over the internet – this will be explained in more detail later on in the article

Read more: BT have announced that they are cutting off ISDN lines by 2025
Here are the main types of business telephone systems:
Digital Telephone Systems

Digital phone systems are those which run calls over traditional copper wires and require the installation of a small box on-site, in order to connect the phone lines to the handsets. There are two main types of digital phone systems:

1. Key Systems Unit (KSU)

KSUs are a basic, yet reliable, phone system which can perform day-to-day operations with ease, and is relatively comparable to the standard home telephone. However, a big disadvantage of KSUs is that they lack portability due to the fact it relies on the central switching device – i.e. the key system unit – to manually determine phone-line selection.

If your SME requires greater flexibility, you could have a KSU-less system which does not require the central cabinet in order to function. Instead, all you need is access to an existing phone jack and you can easily plug and unplug your phone in different locations.

Ideal for: Businesses with 5-40 employees.

2. Private Branch Exchange (PBX)

Traditional digital PBXs are a more automated system than KSUs, given the advanced features it can provide, such as customer waiting queues, business hour settings to route out-of-hour calls, and call conferencing. Therefore, PBXs are more suited for larger businesses which require such features to operate more easily and efficiently.

Again, similar to KSUs, the PBX itself is located on-site, normally living in the office telecom closet. However, unlike KSUs, there are other versions of PBX, including IP PBX, which can enable businesses to run their calls over the internet. These systems will now be explained in further detail below.

Ideal for: Businesses with 40+ employees.

How to Run Calls Over the Internet

New developments in phone technology mean calls can now be run over the internet. As a result of this, the need for traditional copper wires will soon be eliminated. But it is important to highlight that in order to have high-quality calls running over the internet, businesses must have high-bandwidth broadband in order to accommodate both heavy voice and data usage.

One way to run calls over the internet is through an IP PBX. These phone systems are SIP enabled through the use of SIP trunks and are located on-site.

Read more: What is a SIP Trunk?

However, businesses can also opt to have a hosted solution instead. What this means is that the phone system is held in an off-premises data centre rather than on-site in your office. Most businesses have hosted solutions as a way to reduce maintenance costs, avoid the hassle of upgrading software and, in turn, reduce service downtime. This is because all these issues are handled by the service provider.

With hosted solutions, businesses pay a higher monthly fee for the services, but lower upfront costs than a traditional on-site system.

These solutions can allow for a telephone system with a plethora of features such as high-definition calling, Outlook and CRM integration, and twinning – where an employee can receive an inbound call from their office and mobile phone.

Ideal for: Businesses who want to future-proof their telecoms early and/or have an existing strong internet connection.

Hybrid Phone System

A hybrid phone system is a combination of both digital and internet phone systems. These systems can support both legacy and IP-based calling, and normally take the form of a hybrid IP-PBXs. This allows businesses to upgrade to converged solutions while maintaining existing phone networks. As a result, hybrid systems can act as a good stepping stone in the transition from digital phone systems to a full VoIP system.

Furthermore, this solution is arguably more reliable than just pure digital or internet systems as the availability of both can allow for failover. Therefore, if one type of line fails, the hybrid system can automatically route calls to the backup line. As a result, this can minimise the risk of downtime and keep businesses talking.

Ideal for: Businesses who want the benefits of the IP-based calling but want to keep their existing digital phone infrastructure.


If you would like to discuss further which phone systems would best be suited for your business, please gives us a call on 01173 700 200 or email [email protected]