VoIP glossary: what do common hosted telephony terms mean?

The world of VoIP and hosted telephony comes with its own terminology. Here is a plain-English glossary of the most common terms:

• VoIP (Voice over Internet Protocol) – technology for making phone calls over the internet
• SIP (Session Initiation Protocol) – the signalling protocol used to set up, manage, and end VoIP calls
• PBX (Private Branch Exchange) – a business phone system that manages internal extensions and external calls
• Hosted PBX / Cloud PBX – a PBX system managed in the cloud by your provider, with no on-site hardware
• SIP Trunk – a virtual phone line connecting your phone system to the public telephone network via the internet
• IP Phone – a desk phone designed to work over an internet connection
• Softphone – a software application that turns a computer or mobile into a phone
• IVR (Interactive Voice Response) – an automated phone menu that routes callers to the right department
• ACD (Automatic Call Distribution) – intelligent call routing that distributes calls across a team
• PSTN (Public Switched Telephone Network) – the traditional copper telephone network being switched off in 2027
• ISDN (Integrated Services Digital Network) – digital phone lines being retired as part of the PSTN switch-off
• Codec – software that compresses and decompresses voice data for transmission
• QoS (Quality of Service) – network settings that prioritise voice traffic for better call quality
• DID (Direct Inward Dialling) – individual phone numbers that route directly to specific extensions
• UC (Unified Communications) – a platform combining voice, video, messaging, and collaboration tools
• PoE (Power over Ethernet) – technology that delivers power to IP phones through the network cable
• Number Porting – transferring your existing phone numbers to a new provider

Have a question about a term not listed here? Contact Connection Technologies and our team will be happy to help.