In short: Phone system features are the call-handling tools a business phone system provides, such as auto attendants, hunt groups, call queues, call park, voicemail to email and call recording. This glossary also explains the technical terms buyers meet, including DDI, CLI, SIP trunks, SBCs, codecs, QoS, jitter, PSTN, Direct Routing and Operator Connect.
Answering and routing calls
- Auto attendant (IVR): a recorded menu that answers calls and routes them by key press or time of day, such as "press 1 for sales". IVR (interactive voice response) is the broader term and can include speech recognition or data lookups. See call centre phone systems.
- Call park: puts a call on hold in a shared "parking slot" so anyone can pick it up from another phone, which is handy for receptions and warehouses.
- Call pickup: lets you answer a colleague's ringing phone from your own, either within a pickup group or by extension.
- Call queue: holds callers in order with music or messages until an agent is free, then distributes calls by a set strategy. The foundation of any cloud contact centre.
- Failover: what happens when something breaks, for example diverting calls to mobiles or another site if an office connection drops. See multi-site phone systems.
- Hunt group (ring group): a set of phones that ring together or in turn when a department number is called. Simpler than a queue: if nobody answers, the call goes to voicemail or overflow.
- Music on hold: audio or messages played while a caller is on hold or queuing; make sure any music is properly licensed.
Users, devices and presence
- BLF (busy lamp field): lights on a desk phone or console showing whether colleagues are free, ringing or on a call, with one-touch transfer. See VoIP phones.
- DECT: Digital Enhanced Cordless Telecommunications, the standard for cordless business phones. IP DECT bases connect to the phone system over the network. See cordless DECT phones.
- Hot desking: logging in to any shared phone so it takes on your extension and settings for the day.
- PoE (Power over Ethernet): powers desk phones through the network cable from a PoE switch, so no separate power adapter is needed. Back up the switch if phones must work in a power cut.
- Presence: shows whether a colleague is available, busy, in a meeting or away, across phones and apps.
- Softphone: a phone app on a computer or mobile that works like a desk phone, using your business number. See softphone apps.
Recording, reporting and integration
- Call recording: automatic or on-demand recording of calls, with storage, search and retention controls. Callers must be told, and card payments need special handling. See business call recording.
- Screen pop: when a call arrives, the caller's record opens automatically in your CRM or helpdesk. See phone system CRM integration.
- Voicemail to email: voicemail messages delivered to an inbox as audio files, sometimes with a transcription, so they can be shared or picked up anywhere.
- Wallboard: a live display of queue statistics, such as calls waiting and agents available, for a team or supervisor. Common in call centre phone systems.
Numbers and caller ID
- CLI (caller line identification) or caller ID: the number shown to the person you call. Most systems let you present a main number, a department number or your direct number, as long as it belongs to your organisation.
- DDI (direct dial-in): a number that rings an individual or group directly without going through reception.
- Number porting: moving your existing numbers from one provider to another so you keep them when you change system. See number porting.
Lines, trunks and the network
- Codec: the method used to compress voice into data. Common ones include G.711 (standard telephone quality), G.722 (wideband or "HD" voice) and Opus. The codec affects call quality and bandwidth. See hosted VoIP.
- ISDN: the digital line technology (ISDN2 and ISDN30) used by many older phone systems. Openreach is switching it off on 31 January 2027. See ISDN replacement options.
- Jitter: variation in the time voice packets take to arrive. Too much causes choppy audio; a good network and jitter buffers keep it in check.
- PSTN: the public switched telephone network, the traditional copper phone network. It is being switched off on 31 January 2027. See the PSTN switch-off checklist.
- QoS (quality of service): network settings that give voice traffic priority over other data, so calls stay clear when the connection is busy.
- SBC (session border controller): a device or service that sits at the edge of a voice network, securing and translating SIP traffic between systems, for example between a carrier and Microsoft Teams.
- Simultaneous calls: how many calls a system or line can carry at the same time. In 3CX licensing, simultaneous calls include internal as well as external calls. See how many SIP channels do you need?
- SIP trunk: a virtual phone line delivered over the internet that connects a phone system to the phone network. Each channel carries one external call. See SIP trunks.
Microsoft Teams calling terms
- Calling Plan: Microsoft acting as your phone carrier, providing numbers and calls for Teams Phone users. See Teams Calling Plans.
- Direct Routing: connecting a carrier or SIP trunk of your choice to Teams through a certified SBC, run by you or by a provider such as Forever Teams. See Teams Direct Routing.
- Operator Connect: a participating operator provides numbers and calling to Teams, enabled from the Teams admin centre. See Operator Connect.
- Resource account: a Teams account used by an auto attendant or call queue, licensed with a Teams Phone Resource Account licence. See Teams Phone licensing.
- Teams Phone: Microsoft's add-on that gives Teams users PBX features such as cloud voicemail, transfer, auto attendants and call queues. See Microsoft Teams Phone.
Want to know which features matter for your team? Contact us and we will map your call flows to the right platform.
Why choose your cloud phone system with Forever Systems
We are vendor-neutral. Forever Group supplies and supports several cloud phone platforms, so we recommend the one that fits how your organisation works rather than the one we happen to sell.
- Side-by-side comparison of hosted 3CX, Microsoft Teams Phone, Forever UC, Forever Teams and Webex Calling for your users
- Contact centre and call recording options matched to your call volumes and CRM
- Number porting, handsets and set-up handled for you, including the move off analogue and ISDN lines
- Connectivity checked so call quality is right from day one
- UK support for moves, adds, changes and faults
- For BT Cloud Voice, see our BT Business Partner site cloudvoice.cloud
We work with businesses, schools, charities and public sector organisations. We do not sell consumer phone services.
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Contact usFrequently asked questions
What is the difference between a hunt group and a call queue?
A hunt group rings a set of phones together or in turn, and if nobody answers the call goes to voicemail or overflow. A call queue holds callers in order with music or messages until someone is free, and usually adds announcements, wallboards and reporting.
What is an auto attendant on a phone system?
An auto attendant is a recorded menu that answers incoming calls and routes them by key press or time of day, for example "press 1 for sales, 2 for accounts". It lets callers reach the right person without a receptionist and can play different messages out of hours.
What does BLF mean on a phone?
BLF stands for busy lamp field. It is a set of lights or screen keys on a desk phone or console that show whether colleagues are free, ringing or on a call, and let you transfer or pick up calls with one press.
What is the difference between DDI and CLI?
A DDI (direct dial-in) is a number callers dial to reach a person or group directly. CLI (caller line identification) is the number your call presents to the person you are calling. Your DDI is often also your outgoing CLI.
What features should a business phone system have?
Most organisations need an auto attendant, hunt groups or queues, voicemail to email, call transfer, mobile and desktop apps and simple administration. Call recording, CRM integration, wallboards and reporting matter more for sales, support and contact centre teams.