In this handy article, we guide you through the meaning of common words and phrases you’re likely to come across, so that you can be sure you know what questions to ask, that you’re comparing like-with-like and that you’re not paying for more than you need.
Are you sitting comfortably? Then let’s begin…
Cloud-based Telephony – off-site phone services
You’ll have heard of “the Cloud”. What you may not know is that there isn’t really such a thing; or at least, not an actual thing that you can see or touch. “The Cloud” is a term used to describe a global network of computers that are connected over the internet. Together, this network provides an array of different services from data storage, data processing and web-based email, to social media and streaming movies. Cloud-based telephony is a phone system with its nuts and bolts (metaphorically) based somewhere other than in your office and accessed via your internet connection.
VoIP – making phone calls over the internet
If you’ve started your research into the best phone service for you, you’ll have come across “VoIP” (pronounced, conveniently, to rhyme with the word voice). It stands for Voice Over Internet Protocol and is interchangeable with the term IP Telephony. VoIP refers to technology that uses the internet to send voice data that was previously sent over the Public Switched Telephone Network (see below)… or what you and I know as analogue and digital telephone lines. If you’re of a certain age, you may even remember that you used to plug the cable from your computer (via a modem) straight into your phone socket in the wall to get online. That was using the old phone lines to transfer data. Now it’s the other way round… a 180 degree flip, if you like. Now we’re using the internet for voice calls and other communications, even fax. For more detail on this, check out this article from Wikipedia.
PBX – your company’s telephone network
Simply speaking, a PBX, or Private Branch Exchange, is a private telephone network used within an organisation. Traditionally, PBXs comprised a box screwed to the wall in your office, connected to analogue telephone lines. Nowadays, they can be pretty much anywhere; in your office or in the Cloud, and can use any number of different technologies, including VoIP or ISDN (see below). The PBX is technically the internal network of software and hardware that manages your business’ phone system, but in general conversation, “PBX” simply means “phone system”. If your PBX uses Internet Protocol to transfer its data, then you have an IP PBX (Internet Protocol Private Branch Exchange). See how it’s all coming together? To find out more, check out this article from Microsoft.
PSTN – the “old school” phone system
The Public Switched Telephone Network (PSTN) is what analogue phone services ran on since they were first rolled out to the public. It’s phones we used to have in our offices and the phones we generally still have at home. It’s the phone cables that criss-cross our streets above our heads and the copper cables under the pavement. But it’s dying. It simply can’t cope with today’s digital demands. In 2025, it will be made defunct. BT are switching it off (more below).
ISDN – sending data over phone lines since the 1980s
(Not to be confused with ISBN, which is a 10-digit number assigned to every new book published.)
ISDN stands for Integrated Services Digital Network. It’s a service that transmits data and multiple, simultaneous phone calls over those copper wires we talked about (see above). Think of ISDN as an upgrade to the original analogue phone service. It was widely adopted by businesses who needed multiple calls on the same number and direct dial numbers, but rarely used in homes. ISDN has been around in the UK since the 1980s so is familiar to many businesses. However – and this is a BIG DEAL – in 2025, BT are literally hitting the OFF switch for ISDN services that run on the PSTN. They will no longer be available. They will be obsolete. Extinct. So, you really need to get cracking on your switch over to VoIP. Find out more from BT here.
SIP Trunks – the mechanism of VoIP
SIP (Session Internet Protocol) trunking is what enables a PBX (see above) to send and receive calls (or video, or messages) over the internet. (The word “trunk” used to mean a bundle of phone lines. That’s a bit out of kilter with today’s reality, but the word has stuck.) A SIP channel carries one call, so think of that as equivalent to a single phone line. SIP trunks are bundles of SIP channels which use the SIP protocol to send and receive calls.
Unified Communications – all your comms in one place
At PurpleUC, we’re experts in unified communications. (Now you know what the “UC” stands for.) We recommend Microsoft Teams Phone as an excellent, cost-effective solution that is easy to adopt. It utilises the familiar Teams interface for your regular voice calls, brings all your communication into one space (phone calls, video, messaging, voicemail, etc.), and can be used across all your devices (PC, laptop, tablet, phone), wherever you are (home, office, the beach). Find out more about its features here and here.
Start reaping the many benefits of Microsoft Teams Phone straightaway with help from PurpleUC, a platform/vendor agnostic provider of modern IP telephony solutions and connectivity. PurpleUC is a subsidiary of Purple Matrix, a Tier 1 Microsoft Gold partner.