UK business telephony, in plain English.

A

Auto-attendant (IVR)

An automated voice menu that greets callers and routes them by keypress or speech ("press 1 for sales"). Replaces a human receptionist for first-line routing.

C

Call recording

Capture and store inbound and outbound calls for training, dispute resolution and compliance. Must be disclosed to callers in the UK under GDPR and PECR.

CLI (Calling Line Identification)

The phone number presented to the person you call. Ofcom requires UK businesses to present a valid, dialable CLI on every outbound call.

D

DID / DDI (Direct Inward Dialling)

A dedicated phone number that rings a specific user or team without going through a switchboard. Lets every employee have their own external number.

E

E.164

The international standard for phone-number formatting (e.g. +44 20 7946 0958). Required for reliable routing across global carriers.

G

Geographic number (01/02)

A UK landline number tied to a specific area code such as 020 (London) or 0161 (Manchester). Signals local presence even when hosted in the cloud.

H

Hosted PBX

A business phone system run in the cloud by your provider. Replaces on-premises hardware and is managed entirely from a browser.

N

Non-geographic number (03)

UK numbers not tied to a region, typically 03 for businesses. Charged to callers at the same rate as 01/02 numbers.

Number porting

Moving an existing phone number from one provider to another without changing it. Regulated by Ofcom and usually takes 5–10 working days.

O

Ofcom

The UK communications regulator. Sets the rules for number allocation, porting, CLI presentation and the PSTN switch-off.

P

PSTN switch-off

The retirement of the UK's legacy copper telephone network, completing by January 2027. All voice services must move to IP-based delivery.

S

SIP (Session Initiation Protocol)

The signalling protocol that sets up, modifies and ends voice calls over IP networks. The backbone of modern business telephony.

SIP trunk

A virtual phone line delivered over the internet to an on-prem or hosted PBX. Replaces traditional ISDN circuits.

Softphone

A desktop or mobile app that makes and receives calls over the internet using your business number. No desk phone required.

U

UCaaS (Unified Communications as a Service)

A cloud platform that bundles voice, video, messaging and integrations into one product, billed per user per month.