UK VoIP & telecoms glossary

Every UK business-telecoms term, defined in one plain-English sentence. Written so a person — or an AI assistant — gets a correct answer fast.

Core concepts

Network & access

Voice media & quality

Numbering & porting

Regulation & PSTN switch-off

Features

Smart & AI calling

More abbreviations from the dashboard

Short definitions of the other terms you will meet in the Silux Call dashboard. Each is explained with an example in the Help Centre abbreviations A–Z.

01 / 02 — Geographic numbers
UK landline numbers tied to a town or city by their area code, such as 0161 for Manchester or 020 for London.
Example: 0113 (Leeds) and 020 (London) are geographic numbers.
03 / 08 — Non-geographic numbers
UK numbers not tied to a place. 03 costs callers the same as a landline call; 08 numbers can carry extra charges.
Example: 0800 and 03 numbers are non-geographic; they are not tied to a place.
2FA — Two-Factor Authentication
Signing in with your password plus a one-time code sent to your phone, so a stolen password is not enough.
Example: After your password you type a 6-digit code from your phone: that is 2FA.
999 / 112 — UK emergency numbers
Both reach the emergency services in the UK. Over VoIP the operator is given the address you register, not your live location.
Example: Dial 999 or 112 from your Silux Call line and it reaches the emergency services; register your address so they know where to come.
API — Application Programming Interface
A way for other software to talk to your account automatically.
Example: Your developer uses the API to pull call history into your own reports.
API key
A secret password that lets one piece of software use another. Treat it like a password.
Example: Treat an API key like a password: anyone with it can use your account's API.
ATA — Analogue Telephone Adapter
A small box that lets an ordinary corded or cordless home phone, or a fax machine, work as an internet phone.
BACS — Bankers' Automated Clearing Services
The UK system behind Direct Debit payments from a bank account.
Example: Direct Debit payments are collected through BACS, usually in about three working days.
Barge — Barge-in
A supervisor joins a live call so both the caller and the colleague can hear them.
Example: A supervisor barges in to help with an angry caller, and both the agent and caller can hear them.
BLF — Busy Lamp Field
A live light (or icon) showing whether a colleague's extension is free, ringing or on a call — so you know before you transfer.
Example: A green light next to extension 202 means Tom is free; red means he is on a call.
BST — British Summer Time
UK clock time from late March to late October, one hour ahead of UTC.
Example: From late March to late October UK time is BST, one hour ahead of UTC.
CDR — Call Detail Record
One line in your call history: who called whom, when, for how long, whether it was answered, and what it cost.
Example: Each line in Call History (time, from, to, duration, status) is one CDR.
CNAME — Canonical Name record
A DNS setting that points your own web address (such as phones.yourcompany.co.uk) at our platform.
Example: Point phones.yourbrand.co.uk at the portal with a CNAME record at your domain provider.
Concurrent calls — Concurrent calls / lines / channels
How many calls your account can have going at the same moment. On Silux Call it is Entry 1, Plus 2, Growth 3, Pro 5, plus one for each extra landline.
Example: Three people on the phone at the same time = three concurrent calls.
CP — Communications Provider
Any phone or broadband company. "Losing CP" is the provider you are leaving; "gaining CP" is us.
Example: Your old phone company is the losing CP; Silux Call is the gaining CP.
CRM — Customer Relationship Management
Software that holds your customer records, such as HubSpot, Salesforce, Zoho or Pipedrive.
Example: HubSpot, Salesforce and Zoho are CRMs.
CSS — Cascading Style Sheets
Code that controls colours and layout on a web page. Only needed for advanced branding.
Example: CSS controls the colours and fonts on your branded portal.
CSV — Comma-Separated Values
A simple spreadsheet file that opens in Excel, Google Sheets or Numbers.
Example: Export your call history as CSV and open it in Excel or Google Sheets.
DD — Direct Debit
Paying automatically from your bank account each month.
Example: Pay by Direct Debit and your monthly bill is collected from your bank account automatically.
DECT — Digital Enhanced Cordless Telecommunications
The radio standard cordless phones use. A DECT base station plugs into your router and its cordless handsets connect to the base.
Dialplan
The phone system's instructions for what happens to each call. Your dashboard writes it for you — you never edit it by hand.
Example: The dialplan decides that a call to your number plays the greeting menu first.
DID — Direct Inward Dialling
A phone number that rings straight through to a person, team or menu on your system. Each number on your Phone Numbers page is a DID.
Example: Your 0161 number is a DID; it can ring Jane directly without going through reception.
DND — Do Not Disturb
Stops your phone ringing. Callers go to voicemail instead. Outgoing calls still work.
Example: Turn DND on during a meeting and calls go to voicemail until you turn it off.
DNO — Do Not Originate
A list of numbers that organisations such as banks and HMRC only ever receive calls on and never call out from. A call that shows one as its caller ID is fake by definition.
Example: Some HMRC and bank numbers are only ever used to receive calls, so a call from one is blocked by Scam Shield.
DNS — Domain Name System
The internet's address book, managed wherever you bought your domain name.
Example: DNS is the internet's address book that turns a web address into a server.
Duplex — Full duplex
Two-way audio — both sides can speak at the same time. In paging, duplex turns a one-way announcement into an intercom.
Example: In duplex paging the person you page can talk straight back, like an intercom.
E.164 — International number format
A phone number written with + and the country code and no leading zero, such as +44 161 496 0000. Some fields accept this format.
Example: 01632 960123 written in E.164 format is +441632960123.
HD voice — High-definition (wideband) voice
Clearer, fuller call audio than a traditional phone line when both ends support it.
Example: Two softphone users talking on HD Voice sound noticeably clearer than an old landline.
Latency — Latency (ms)
How long your voice takes to reach the other end, in milliseconds. Under 150 ms feels natural.
Example: 30 ms latency is fine; over 150 ms you start talking over each other.
Listen-in — Silent monitoring
A supervisor hears a live call without either person hearing them.
Example: A manager listens in on a new starter's call without either person hearing them.
LOA — Letter of Authority
A signed letter from the account holder agreeing to move their numbers to us. Your current provider will not release numbers without it.
Example: You sign the LOA online when you ask to bring your number over from BT.
MOH class — Music-on-hold class
The named set of hold music the phone system plays. You set it by choosing a default track on the Hold Music page.
Example: Choose a default track on Hold Music and that becomes the MOH class callers hear on hold.
MP3 / WAV — Audio file formats
The two most common sound file types. WAV is full quality and larger; MP3 is smaller.
Example: Download a recording as MP3 to email it; keep the WAV if you need the original quality.
MRR — Monthly Recurring Revenue
What all of a reseller's customers pay each month, added together.
Example: 20 customers paying £10 a month = £200 MRR.
ms — Milliseconds
Thousandths of a second.
Example: 150 ms is 0.15 of a second.
NAT — Network Address Translation
What your router does to share one internet address between all your devices. It is the usual cause of one-way audio.
Example: Your router uses NAT so every device in the office shares one internet address.
Ofcom — Office of Communications
The UK telecoms regulator. Its rules cover 999 access, number porting and caller ID.
Example: Ofcom sets the UK rules on number porting and emergency calls.
OTP — One-Time Passcode
A short code that works once, sent by text for signing in or confirming something.
Example: The 6-digit code texted to you when you sign in is an OTP; it works once and expires.
Overage — Overage / out-of-bundle
Usage beyond what your plan includes, such as minutes past your allowance, charged at your standard rate.
Example: If your plan includes 500 minutes and you use 520, the extra 20 are overage.
Overflow — Overflow routing
Where a call goes when a queue is full or has waited too long — voicemail, another number, or hang up.
Example: If nobody in Sales answers within 2 minutes, the call overflows to the Office group.
Packet loss — Packet loss (%)
The share of call audio that never arrives. Under 1% is good; above 3% causes gaps.
Example: 1% packet loss is barely noticeable; 5% makes words drop out.
Paging — Paging / intercom
A one-way announcement that comes out of many handsets at once, like a tannoy. Duplex (intercom) mode lets people reply.
Example: Dial the paging group and say "Delivery at the back door" to every phone in the group.
PBX — Private Branch Exchange
A business phone system — the "switchboard" that decides which phone rings, holds callers, transfers them and plays menus. Ours is hosted (in the cloud), so there is no box in your office.
Example: Your Silux Call account is a hosted PBX: extensions, menus and transfers all run on our servers, so there is no box in your office.
PCI DSS — Payment Card Industry Data Security Standard
The card schemes' security rules for anyone who takes card payments. Taking card numbers by keypad (so staff never hear them) and pausing recordings during payment keeps card data out of your business.
Example: Taking card numbers by keypad, with recording paused, keeps card data out of your recordings, as PCI DSS requires.
PDF — Portable Document Format
A document file for invoices and statements.
Example: Invoices download as PDF files you can print or send to your accountant.
PIN — Personal Identification Number
A short number code — used for voicemail access and conference rooms.
Example: Your voicemail PIN, e.g. 4826, stops anyone else listening to your messages.
PoE — Power over Ethernet
Power sent down the network cable, so a desk phone needs no separate power plug. Needs a PoE switch or a PoE injector; otherwise use the phone's power adaptor.
Range holder
The network operator that owns the block your number comes from — often not the company that bills you. You never need to know it; we can look it up.
Example: Your bill may come from one company while the number block belongs to another network; that network is the range holder.
Ring strategy
The rule for which phone rings next: Ring All (everyone at once), Sequential (in order), Round Robin (take turns), Least Recent (whoever has waited longest since their last call) or Fewest Calls.
Example: Ring all, one by one, or taking turns: each is a ring strategy.
RIPA — Regulation of Investigatory Powers Act
UK law covering interception of communications — the reason staff must be told that calls may be monitored or recorded.
Example: Put a line in staff contracts and your greeting saying calls may be monitored or recorded.
Screen pop
The caller's customer record opening on your screen automatically as the phone rings.
Example: The caller's customer record opens on your screen as the phone rings.
SIP 603 — SIP response 603 "Decline"
The signal Scam Shield sends back when it blocks a call: the call is refused before your phone rings.
Example: Scam Shield blocks a spoofed call with SIP 603, so the scammer hears the call refused and your phone never rings.
SIP ALG — SIP Application Layer Gateway
A router setting that tries to "help" internet phones but often breaks them: one-way audio, calls dropping after about 30 seconds, or phones that keep going offline. Turn it off.
SLA — Service Level Agreement
The service availability we commit to for your plan, published on our legal pages.
Example: An SLA sets out the uptime and response times a service commits to.
SMS — Short Message Service
An ordinary text message.
Example: A missed-call alert that arrives on your mobile as a text is an SMS.
Spoofing — Caller ID spoofing
When a scammer fakes the number shown on your screen — for example making a call look as if it comes from HMRC. Scam Shield catches the most common forms.
Example: A call that shows your bank's number but asks for your PIN is almost certainly spoofed.
STUN — Session Traversal Utilities for NAT
A helper server that tells your phone its public internet address so calls can connect through your router.
Example: STUN lets your softphone find its public internet address so calls connect through your router.
Tenant — Tenant / organisation
Your company's account on the platform. The Tenant ID is its reference number — support may ask for it.
Example: Your business is one tenant on the platform; nobody else can see your calls or settings.
Transcription — Speech to text
Turning recorded speech into written text you can read and search.
Example: A voicemail transcription lets you read "Hi, it's Sarah about the quote" instead of listening.
TTS — Text to speech
Typing words and having them spoken in a natural voice. The Greetings studio and Greeting Menus use it.
Example: Type "We are closed for lunch" and TTS turns it into speech in the voice you choose.
TURN — Traversal Using Relays around NAT
A relay server that carries call audio when a strict router or firewall would otherwise block it.
Example: If your office firewall blocks direct audio, a TURN server relays it so the call still works.
UDP — User Datagram Protocol
The quick, simple way most desk phones send their sign-in and call signals over the internet. Choose UDP when a phone asks for the "transport".
UK GDPR — UK General Data Protection Regulation
The UK's data protection law. For recordings it means: tell people, have a reason, and keep them no longer than you need.
Example: Keeping recordings only as long as you need them (for example 90 days) is part of meeting UK GDPR.
URL — Uniform Resource Locator
A web address, such as https://example.com/hook.
Example: https://www.siluxcall.co.uk/help is a URL.
UTC — Coordinated Universal Time
World standard time. The UK is on UTC in winter and UTC+1 (BST) in summer — choose Europe/London and the change happens for you.
Example: In July, 14:00 UTC is 15:00 UK time; pick Europe/London as your time zone and you never need to work it out.
VAT — Value Added Tax
UK sales tax, charged at 20% on top of prices shown excluding VAT.
Example: Prices are shown excluding VAT; 20% VAT is added at checkout and on your invoice.
Webhook
An automatic message our system sends to a web address you choose whenever something happens, such as a call ending. Used to connect other software.
Example: When a call ends, a webhook sends its details to your own system automatically.
WebRTC — Web Real-Time Communication
The technology that lets your web browser make and take phone calls without installing anything. The Softphone page uses it.
Example: The dashboard softphone uses WebRTC, which is why it works in Chrome with nothing to install.
what3words — what3words address
Three words that pinpoint a 3-metre square anywhere in the world — useful for large sites and rural premises.
Example: A what3words address such as ///filled.count.soap pinpoints a 3 metre square, useful for rural premises.
WhatsApp
The messaging app. Call alerts and the WhatsApp Business inbox send and receive messages through it.
Example: A missed-call alert can arrive as a WhatsApp message instead of a text.
Whisper — Whisper / whisper coaching
Speaking to your colleague during a live call without the caller hearing. Call Whisper (the menu item) is different: a short message played to whoever answers before the caller is connected.
Example: A supervisor whispers "offer the discount" and only the agent hears it.
White label
Our platform sold by a partner under the partner's own name, logo and colours.
Example: A reseller sells our phone system under their own brand: that is white-label.
Wrap-up — Wrap-up time
A pause after a queue call ends before that person is given another, so they can finish notes.
Example: A 30-second wrap-up time lets an agent finish their notes before the queue sends the next call.