Glossary

UK geographic numbers, tied to an area code such as 020 for London or 0161 for Manchester. Calls to them are normally inside plan minutes.

At VoicePro: VPX Numbering provides UK 01 and 02 geographic numbers.

UK non-geographic numbers charged at the same rate as 01 and 02 calls and included in plan minutes. Popular with charities, public bodies and businesses that want one national number.

At VoicePro: VPX Numbering provides UK 03 numbers.

The UK range for mobile numbers (071 to 075 and 077 to 079), plus 070 personal numbers and 076 pagers, which are charged differently and are often misused in scams.

UK non-geographic numbers. 0800 and 0808 are free to call; 084 and 087 carry a service charge set by the business plus your provider's access charge.

UK premium rate numbers for paid services such as competitions and adult lines. They carry high service charges and are regulated by Ofcom.

Two-factor authentication. Signing in with a second proof as well as a password, such as a code from an app, a security key or a text. App or key-based methods are safer than SMS codes, which SIM swap can intercept.

The second generation of mobile networks, built on the GSM standard from the early 1990s. It carries calls, texts and very slow data, and is still used by some alarms, meters and older IoT devices while networks keep it running.

An extra check on online card payments, usually a code or banking app approval, that the card issuer runs before accepting the payment. It is how strong customer authentication works for cards.

The third generation of mobile networks, which brought usable mobile internet. All UK networks have now switched 3G off and reused its spectrum for 4G and 5G.

3rd Generation Partnership Project. The body that writes the technical standards for 4G, 5G, IMS and much of mobile networking.

The fourth generation of mobile networks, based on LTE. It is all-IP, so calls run as data (VoLTE), and it remains the backbone of mobile coverage alongside 5G.

The fifth generation of mobile networks. It offers higher speeds, lower latency and room for far more connected devices than 4G. Its radio standard is called NR (New Radio).

5G Non-Standalone. 5G radio that relies on a 4G core network for control. It was the first form of 5G most operators launched, and the phone keeps a 4G connection at the same time.

5G Standalone. 5G radio connected to a dedicated 5G core, with no reliance on 4G. It enables lower latency, network slicing and better battery life.

A way of billing bandwidth: usage is sampled every few minutes, the top 5 percent of samples are ignored, and you pay for the highest remaining level. Short bursts do not raise the bill.

At VoicePro: VPX Drive Connect+ IP transit is billed on the 95th percentile.

A wholesale offer that covers calls to every destination in the world, from Afghanistan to Zimbabwe, under one agreement and rate deck.

At VoicePro: VPX Carrier Voice offers A-Z routes to 200+ countries.

Application-to-Person SMS. Texts sent by software to people, such as one-time passcodes, delivery updates and appointment reminders. Networks often price and filter it separately from person-to-person texts.

At VoicePro: VPX Carrier SMS carries wholesale A2P and P2P SMS.

Prepaid funds held on an account and drawn down as services are used or bought.

A criminal gaining control of someone's account, often with stolen passwords or by intercepting codes, then changing the contact details to lock the owner out.

Average Call Duration. The mean length of answered calls on a route, in minutes or seconds. Read with ASR: a sudden fall can mean false answers or poor audio. Also called ALOC (average length of call).

Alternative Dispute Resolution. An independent body that settles complaints between customers and providers free of charge. In UK telecoms there are two Ofcom-approved schemes; a customer can go to one after eight weeks, or sooner with a deadlock letter.

Artificially Inflated Traffic. Fake calls or texts generated to earn revenue, for example bots triggering thousands of OTP texts to numbers that share in the termination fee.

At VoicePro: VPX Global Insight+ runs AIT checks on numbers.

A sender name made of letters and numbers, up to 11 characters, such as a brand name. Recipients cannot reply to it, and some countries block or require registration of it.

Anti-Money Laundering. Laws and controls that stop criminals moving or disguising illegal money, including customer checks, monitoring and reporting suspicious activity.

Adaptive Multi-Rate codecs used for mobile calls. AMR-WB (wideband) gives HD Voice quality on 3G and VoLTE.

Automatic Number Identification. The calling party number carried in call signalling, used for billing and routing. It can differ from the number shown to the person you call.

Access Point Name. The settings your phone uses to connect to mobile data and picture messages (MMS). Most phones set it automatically from the SIM; you only need to enter it by hand if mobile data does not work.

The part of a geographic number that identifies a place, such as 020 for London. Dialled with the leading 0 within the country.

Answer Seizure Ratio. The percentage of call attempts that are answered. A key route quality measure, though it also reflects the callers' traffic (for example diallers often have low ASR).

Using connected devices with GPS or cell location to follow vehicles, containers, tools or equipment.

A recorded menu that answers calls and routes callers by keypress, such as "press 1 for sales".

At VoicePro: Our cloud phone system includes auto attendant menus, set up for you.

A phone system feature that shares incoming calls across a group of agents by rules such as longest idle or skills. Often shortened to ACD in contact centres, not to be confused with Average Call Duration.

An Ofcom-backed scheme under which participating UK broadband and landline providers pay customers set amounts for delayed repairs, missed appointments and late installations, without the customer having to claim.

A deal in which two carriers both send and receive traffic with each other, often settled by netting what each owes.

The regular period, usually monthly, over which usage is collected and a bill or renewal is raised.

A formal challenge to a carrier invoice, usually raised within an agreed window when CDRs do not reconcile.

How call time is rounded for charging, written as first period/next period. 1/1 is per-second; 60/60 is per-minute; 30/6 charges the first 30 seconds then each 6 seconds.

At VoicePro: VPX Carrier Voice bills per second.

A subset of a destination with its own rate, such as UK mobile versus UK fixed, or one mobile network within a country. Each breakout is defined by its dial codes.

A package of data, minutes or texts for a set period, such as a monthly allowance or a travel data pack for a region.

Holding callers in line, usually with music and position announcements, until an agent is free.

Storing the audio of calls for training, compliance or disputes. In the UK, callers must normally be told calls may be recorded, and recordings are personal data under UK GDPR.

A company that carries telecom traffic for others, from national operators to specialist wholesale voice and SMS providers.

Combining several frequency bands into one connection to raise download speeds. Supported by most 4G and 5G phones.

Network settings files published by phone makers that tell a phone how to work with a particular network. Your phone matches them to your SIM and installs updates automatically.

Contact Centre as a Service. Cloud-hosted contact centre software: queues, IVR, agent desktops, recording and reporting, paid by subscription.

Customer Due Diligence. The checks a regulated business runs to confirm a customer's identity and assess risk, with enhanced checks (EDD) for higher risk.

Call Detail Record. The record a switch writes for every call: numbers, start time, duration, route and outcome. CDRs are the basis of billing and reconciliation between carriers.

At VoicePro: VPX Carrier Voice exports full CDRs by SFTP or API.

Comparing your own CDRs against a partner's invoice or CDRs to find differences in minutes or charges before paying.

The area covered by one antenna sector on a mast. Phones move from cell to cell as you travel, and each cell has its own identifier (Cell ID).

A way of sending one message to every phone in an area at once, without knowing their numbers. The UK Emergency Alerts service uses it.

A card payment reversed by the cardholder's bank after a dispute, for example for fraud or goods not received. The merchant loses the money and usually pays a fee.

Committed Information Rate. The bandwidth a provider guarantees on a connection, as opposed to burst capacity that may be available when the network is quiet.

At VoicePro: VPX Drive Connect+ offers committed rates from 10 Mbps to 100 Gbps.

A switch that routes large volumes of calls between carriers and long-distance networks, with routing, rating and CDR features but no end-user services.

Calling Line Identification. The phone number presented to the person you call. It can be shown, withheld, or sent in international or national format.

A route that delivers the caller's number intact to the person called. Non-CLI routes may drop or alter it and are usually cheaper. Many countries now require CLI to be passed.

Faking the caller ID on a call so it appears to come from a trusted number, such as a bank. Used in fraud and scam calls.

At VoicePro: VPX Global Insight+ helps block spoofed calls in the call path.

A button on a website or app that starts a phone call, either from the browser or by calling the user and connecting them.

Calling Line Identification Presentation and Restriction: showing the caller's number, or withholding it. In the UK dial 141 before a number to withhold yours for one call.

A business phone system hosted by a provider instead of on a box in the office. Extensions, menus and voicemail are managed online and work on desk phones, apps and browsers. Also called hosted PBX.

At VoicePro: Our cloud phone system is set up by our team and runs on desk phones, browsers and mobiles.

Coder-decoder. The method used to compress voice into data and back. Codecs trade bandwidth against audio quality; both ends of a call must agree on one.

The main UK law for electronic communications. It created Ofcom's powers and the general authorisation regime under which providers operate without an individual licence.

The procedure every UK communications provider must publish and follow for handling customer complaints, including telling customers about their right to ADR.

A long text split into several segments and joined back together on the phone. Each segment is charged as one message.

The number of calls that can be in progress at the same time on a trunk or system, sometimes called channels.

An extra code some eSIMs need during installation, alongside the QR code or activation code. If your eSIM needs one, it is given to you with your eSIM details.

The central part of a mobile network that authenticates users, routes calls and data, and handles billing records. The radio network connects phones to it.

The 1 to 3-digit prefix that identifies a country in international numbers, such as 44 for the UK and 1 for North America. Dialled after + or the international access code.

Where a network's signal is strong enough to use. Operators publish coverage maps, usually split by 2G, 4G and 5G and by indoor and outdoor.

Calls Per Second. The rate at which a switch or platform can set up new calls. A measure of capacity at peak load, important for diallers and contact centres.

The most a carrier will let a customer owe before blocking traffic, set from credit checks, deposits or prepayment.

A document that reduces or cancels an amount on an invoice already issued, for example after a refund.

Corporate Telephone Preference Service. The UK register where businesses can opt out of unsolicited sales calls, the business counterpart of the TPS.

Sharing one data allowance across a fleet of SIMs, so heavy and light users balance out instead of each SIM having its own limit.

The UK law that sits alongside UK GDPR, adding UK-specific rules and exemptions and setting out the ICO's powers.

Keeping records such as call and connection data for a set period, either because the law requires it or for billing and disputes. Personal data must not be kept longer than needed.

Using mobile data on a foreign network. Phones have a separate switch for it so you can stop data use abroad.

An eSIM that provides mobile data but no phone number, so calls and texts stay on your usual SIM. Common for travel.

At VoicePro: Our travel eSIMs are data-only and install by QR code beside your everyday SIM.

Distributed Denial of Service. Flooding a service with traffic from many sources to knock it offline.

At VoicePro: VPX Drive Connect+ includes DDoS mitigation.

A physical handset that connects to the network and registers to a phone system over SIP.

The number prefix used to match a call to a destination and rate, such as 447 for UK mobile. Longest match wins.

Direct Inward Dialling (DID in North America, DDI in Europe). A phone number that routes straight to an extension, user or system without going through a switchboard. Also used to mean any virtual number delivered over SIP.

At VoicePro: VPX Numbering provisions DID and DDI numbers in 60+ countries, by portal or API.

A UK payment method where you authorise a company to collect variable amounts from your bank account, protected by the Direct Debit Guarantee.

Delivery Receipt. A status report from the network saying whether an SMS was delivered, expired or failed.

At VoicePro: VPX Carrier SMS returns real-time delivery receipts.

Do Not Originate. A list of numbers that should only receive calls, never make them, such as bank and government inbound lines. A call claiming to come from one is almost certainly spoofed and can be blocked. Ofcom publishes a UK list.

At VoicePro: VPX Global Insight+ checks numbers against DNO lists.

In number porting, the donor is the network a number is leaving and the recipient is the network it is moving to.

Delegated Proof of Stake. A consensus mechanism where token holders vote for a limited set of validators (delegates) who produce blocks and validate transactions. The VPX Protocol uses DPoS for energy-efficient consensus.

Datagram Transport Layer Security for Secure Real-time Transport Protocol. A way of agreeing encryption keys for voice and video media, used by WebRTC for end-to-end encrypted calls.

Dual-Tone Multi-Frequency. The tones generated when pressing phone keypad buttons, used to navigate IVR menus. Over VoIP they are usually sent as separate events (RFC 4733, formerly RFC 2833) rather than as audio.

A phone that can hold two SIMs or eSIM profiles active at once (DSDS, dual SIM dual standby), so you can keep your number while using another line for data.

The ITU-T standard for international phone numbers: a + sign, country code and national number, up to 15 digits in total, for example +442037698080.

Audio played before a call is answered, such as ringback tones or network announcements, signalled in SIP with a 183 Session Progress response.

Extended Discontinuous Reception. Lets an IoT device sleep for set periods between checks for incoming data, saving battery while staying reachable.

European Electronic Communications Code. The EU directive that sets the common rules for telecom networks, services and consumer protection across member states.

eUICC Identifier. The unique 32-digit number of the eSIM chip in your device, shown in your phone's settings. It is used to send an eSIM to the right device.

eSIM IoT Manager. The SGP.32 component that remotely tells IoT devices which eSIM profiles to download, enable or delete, without needing a screen or user.

Calls to emergency services. UK providers must connect 999 and 112 free of charge and pass caller location where possible, including from VoIP services.

Electronic Money Institution and Payment Institution. FCA authorisation categories for firms that issue e-money or provide payment services in the UK.

The person who uses a SIM or eSIM, whether they bought it directly from the provider or through a reseller.

Encryption where only the people communicating hold the keys, so no one in between, including the service provider, can read or listen.

The base station equipment on a mast: eNodeB for 4G, gNodeB for 5G. It handles the radio link between phones and the network.

Evolved Packet Core. The core network for 4G, made up of functions such as the MME, gateways and HSS.

In the VPX Protocol, a fixed time window during which block production and reward distribution occur. Validators are evaluated per epoch for uptime and performance.

A unit of call traffic: one Erlang is one line busy for one hour. Used to size how many lines or agents a business needs.

Embedded SIM. A SIM built into your phone or device instead of a plastic card. You install a mobile plan onto it by scanning a QR code or through an app, and many phones can hold several eSIM profiles. Governed by GSMA standards SGP.22 (consumer) and SGP.02 and SGP.32 (IoT).

At VoicePro: Travel eSIMs are on sale now, installed by QR code before you fly.

European Telecommunications Standards Institute. Develops standards for telecom and radio, including the original GSM and smart card specifications.

Embedded Universal Integrated Circuit Card. The secure chip that holds eSIM profiles and lets them be downloaded, switched and deleted remotely. eSIM is the everyday name for it.

Enhanced Voice Services. A modern mobile codec for VoLTE and 5G that gives clearer audio than AMR-WB and copes better with poor signal.

The rate used to convert between currencies. Wholesale and international services often price in USD or EUR and settle in another currency.

Terms that set a reasonable limit on an unlimited or roaming allowance, to stop resale or abuse. Use beyond it may be slowed or charged.

False Answer Supervision. A route that signals a call as answered while it is still ringing or failed, so the caller is charged for time that was not a real call. A sign of fraud or a poor-quality route.

Financial Conduct Authority. The UK regulator for financial services firms and markets, including payments, e-money and consumer credit.

A text that appears straight on the screen and is not saved by default. Used for some alerts.

Tracking and managing vehicles or devices remotely: location, status, usage and alerts, usually through a web platform.

Fixed-Mobile Convergence. Joining fixed-line and mobile services so one number, one phone system or one bill covers both, for example a desk extension that also rings on a mobile.

A call routing feature that rings a series of devices in turn, such as desk phone, then mobile, then app, until the call is answered.

At VoicePro: Follow-me routing is part of our cloud phone system.

Software that watches traffic and accounts in real time for patterns of fraud, such as sudden calls to high-cost destinations, and blocks or alerts.

A number that is free for the caller, with the receiving business paying instead. In the UK, 0800 and 0808.

A numbered block of radio spectrum a network uses, such as band 20 (800 MHz) or n78 (3.5 GHz). A phone can only use a network if it supports that network's bands.

An MVNO that runs its own core network, issues its own SIMs and IMSIs and controls its own services, buying only radio access from the host network. A light MVNO relies on the host or an MVNE for most of this.

The standard uncompressed voice codec of the phone network, at 64 kbit/s. A-law is used in Europe and mu-law in North America. It gives reliable quality and is supported everywhere.

At VoicePro: VPX Carrier Voice interconnects with G.711 a-law and mu-law.

A wideband codec for HD voice on IP phones, at 64 kbit/s with roughly twice the audio range of G.711.

A compressed voice codec at 8 kbit/s, used where bandwidth is tight. Quality is lower than G.711 and it does not carry fax or tones well.

General Data Protection Regulation. The EU law on personal data; the UK kept its own version, UK GDPR, after Brexit. It sets out lawful reasons to use personal data and people's rights to access, correct and delete it.

The rules Ofcom sets that every UK communications provider must follow, covering emergency calls, numbering, contracts, switching, complaints, billing accuracy and vulnerable customers.

A number linked to a place by its area code. Businesses often use them to look local in each town they serve.

A route that delivers traffic in a way the receiving network has not authorised, for example through SIM boxes or by disguising international calls as local ones. Cheaper, but quality and caller ID are unreliable and it may be illegal in the destination.

The basic SMS character set of Latin letters, digits and common symbols. One segment holds 160 GSM-7 characters.

The GSM Association, the global industry body for mobile operators. It publishes the standards behind eSIM, roaming and SIM security, and runs the global IMEI database used to block lost and stolen phones.

Passing a live call or data session from one cell to another as you move, without dropping it.

Home Location Register. The central database in 2G and 3G networks holding each subscriber's profile, services and current location. HLR lookups reveal whether a number is active, roaming, ported or disconnected.

At VoicePro: VPX Global Insight+ returns live status and network for a number by portal or API.

Sharing your phone's mobile data with other devices over Wi-Fi, Bluetooth or USB. Some plans limit or exclude it.

Home and Visited Public Land Mobile Network. Your home network, and the foreign network you use when roaming.

Home Subscriber Server. The 4G and IMS successor to the HLR: the database of subscriber identities, keys and service profiles. In 5G its role is taken by the UDM.

Connecting to one hub carrier that reaches many networks, instead of building direct links with each one.

A group of extensions that share incoming calls, ringing all at once or one after another.

Integrated Circuit Card Identifier. The 19 or 20-digit serial number of a SIM card or eSIM profile. It identifies the SIM itself, not your phone or your phone number.

Information Commissioner's Office. The UK regulator for data protection and for electronic marketing rules under PECR.

Confirming a person is who they say they are, often by checking an ID document and matching it to a live selfie (a liveness check).

The Internet Engineering Task Force publishes internet standards as numbered RFCs (Requests for Comments). SIP, for example, is RFC 3261.

International Mobile Equipment Identity. The unique 15-digit number of a mobile device. Dial *#06# to see it. Networks use it to block phones reported lost or stolen, and dual-SIM phones have two.

IP Multimedia Subsystem. The part of a mobile core that runs voice and messaging over IP, including VoLTE, Wi-Fi Calling and RCS. It uses SIP for signalling.

International Mobile Subscriber Identity. A unique number of up to 15 digits stored on the SIM that identifies you to the mobile network. It includes the country and network codes, and it is not your phone number. See also Multi-IMSI.

A technical and commercial link between two networks so traffic can pass between them, usually covered by an interconnect agreement.

At VoicePro: VPX Carrier Voice interconnects over SIP, with applications open online.

The UK law governing lawful interception and the acquisition of communications data by authorised public bodies, with warrants and independent oversight.

A bill requesting payment for goods or services. A VAT invoice must show the supplier's VAT number, the VAT charged and other set details.

Internet of Things. Everyday objects and machines with built-in connectivity, such as trackers, meters, sensors, payment terminals and vehicles.

At VoicePro: Our IoT SIMs reach 718 networks in 203 countries, including all 4 UK networks.

A SIM designed for devices rather than phones, usually with multi-network access, remote management and pricing built for small amounts of data.

At VoicePro: One VoicePro IoT SIM uses the same APN in 203 countries.

A private branch exchange that runs over IP, connecting extensions to each other and to the outside world through SIP trunks.

Paid access to the whole internet through a provider's network, as opposed to peering, which only reaches the other network's own customers.

At VoicePro: VPX Drive Connect+ provides dedicated IP transit.

IoT Profile Assistant. The SGP.32 component in the device or eUICC that downloads eSIM profiles on instruction from the eIM.

International Premium Rate Number. A number that pays its holder a share of each call's charge. Legitimate uses exist, but IPRNs are the payout end of IRSF.

IP Packet Exchange. A private, quality-managed IP network that mobile operators use to exchange roaming data, voice and messaging. It succeeded the GRX.

International Revenue Share Fraud. Fraudsters push large volumes of calls, often from hacked phone systems or stolen SIMs, to high-cost international numbers and collect a share of the termination fees. One of the costliest telecom frauds worldwide.

At VoicePro: VPX Global Insight+ checks numbers against IRSF lists.

Integrated Services Digital Network. A digital telephone service over copper lines, widely used for business phone systems. BT is withdrawing it as the UK moves to all-IP.

ISDN User Part. The part of SS7 that sets up and clears calls between telephone exchanges. Its cause codes are still mapped to SIP responses today.

International Toll-Free Service. A freephone number in one country that a business abroad can receive calls on.

International Telecommunication Union. The UN agency for telecoms. Its ITU-T sector writes standards such as E.164 numbering and voice codecs, and it coordinates global spectrum.

Interactive Voice Response. An automated phone system that talks to callers and acts on keypresses or speech, from simple menus to account lookups and payments.

Variation in how long voice packets take to arrive. High jitter makes speech choppy; phones use a jitter buffer to smooth it out at the cost of a little delay.

The secret authentication key stored on a SIM and in the operator's core. It never leaves either, and is used to prove the SIM is genuine and to create encryption keys.

Know Your Business. Verifying a company customer: its registration, directors, ownership and who ultimately controls it.

Know Your Customer. Checking a customer's identity and assessing their risk before and during a relationship. Required for financial services and increasingly used in telecoms to stop fraud.

The delay for audio to travel from one end of a call to the other. Above about 150 ms one way, people start talking over each other.

Access to communications by law enforcement under a legal warrant. Networks must be able to support it under national law.

Least Cost Routing. Choosing the cheapest available route for each call while still meeting quality thresholds.

Whether a number is currently connected and reachable, found by querying the network in real time. Used to clean contact lists and stop fraud.

At VoicePro: VPX Global Insight+ returns live status by portal, API or on SIP trunks.

Local Number Portability. The North American term for keeping a number when changing provider. Calls are routed after a database lookup called an LNP dip.

Letter of Authorisation. A signed form from the number holder that authorises a provider to port their numbers.

A standard-length phone number used to send and receive texts, as opposed to a short code. Also called a virtual mobile number for two-way SMS.

Low-Power Wide-Area Network. Networks for devices that send small amounts of data over long distances on very little power, such as NB-IoT, LTE-M and LoRaWAN.

Long Term Evolution, the 4G mobile standard. Still the backbone of mobile coverage alongside 5G, and the network VoLTE calls run over.

Lower-cost 4G categories for IoT with moderate speeds (about 10 Mbit/s down) and voice support. Cat-1 bis uses a single antenna to cut cost and size. A common replacement for 2G and 3G modules.

LTE for Machines (Cat-M1). A low-power 4G variant for IoT that supports mobility, moderate data and voice, with better building penetration and long battery life.

At VoicePro: Our IoT SIMs use LTE-M on the UK networks that offer it.

Machine-to-Machine. Devices exchanging data with systems automatically, without people involved. The older term for much of what is now called IoT.

Mobile Country Code and Mobile Network Code. Together they identify a network worldwide; the UK MCC is 234 (and 235). They form the start of every IMSI.

The billing step that collects raw usage records from network equipment, cleans and standardises them, and passes them on for rating.

One SMS unit: up to 160 GSM-7 characters or 70 Unicode characters. Longer messages use more segments, each with a little space reserved for joining them up.

Multi-factor authentication. Signing in with two or more independent proofs of identity. 2FA is the most common form.

Machine Form Factor 2. A SIM chip soldered onto a device's circuit board instead of inserted, resistant to vibration, heat and theft. Often an eUICC.

An increase in price during a fixed contract. Since January 2025 Ofcom requires any such rise in UK mobile and broadband contracts to be stated upfront in pounds and pence, not as an inflation-linked percentage.

Mobility Management Entity. The 4G core function that handles sign-on, authentication and tracking of devices as they move.

Multimedia Messaging Service. Picture, audio and video messages sent through the mobile network. It needs mobile data and the right APN settings.

Mobile Network Operator. A company that owns and runs its own radio network and spectrum, such as the UK's national mobile networks. MVNOs buy access from MNOs.

Mobile Number Portability. Keeping your mobile number when switching network. MNP lookups confirm which network currently serves a number, so calls and texts are routed and priced correctly.

At VoicePro: VPX Global Insight+ checks portability and port history.

Mean Opinion Score. A 1 to 5 rating of call audio quality, now usually estimated by software from packet loss, jitter and latency. Above 4 is good.

Messages Per Second. The rate at which an SMS connection can submit messages, a measure of throughput.

At VoicePro: VPX Carrier SMS supports up to 3,000 MPS per connection.

Mobile Switching Centre. The switch in 2G and 3G networks that sets up and routes voice calls and texts.

Your mobile number in full international format, including the country code, for example +44 7700 900123.

A SIM that holds several IMSIs, each from a different network, and switches between them for the best coverage or price in each country. Common on travel and IoT SIMs.

A SIM that can use more than one network in a country, so a device can move to another network when its current one is weak or down.

At VoicePro: Our IoT SIMs can attach to any of the 4 UK networks.

Mobile Virtual Network Aggregator. A wholesaler that buys capacity from a network operator and resells it to several MVNOs.

Mobile Virtual Network Enabler. A company that provides the technical platform (core network, SIMs, billing, provisioning) that an MVNO runs on.

Mobile Virtual Network Operator. A mobile provider that does not own radio spectrum or masts but buys wholesale access from an MNO and sells service under its own brand.

The smallest removable SIM card size (12.3 by 8.8 mm), used by almost all current phones. Larger sizes are mini and micro SIM; many cards are triple-cut to fit all three.

Techniques that let VoIP calls pass through routers that hide devices behind one public address. Without it, calls often have one-way or no audio.

A phone number without the country code and without the leading 0, such as 20 3769 8080 for a London number.

Narrowband IoT. A low-power mobile technology for static devices that send small amounts of data, such as meters and sensors. It reaches deep indoors and underground and runs for years on a battery, but does not support voice or fast movement.

At VoicePro: Our IoT SIMs use NB-IoT where UK networks run it.

Network Effectiveness Ratio. The share of calls the network delivered to the far end, whether answered, busy or unanswered. Unlike ASR it ignores user behaviour, so it isolates network faults.

The principle that internet providers treat all traffic equally. UK open internet rules allow reasonable traffic management but not unfair blocking or favouring of services.

Rules on an IoT SIM that limit which networks it may use, for example to control cost or keep traffic in certain countries.

A device registering on a mobile network so it can send data. A rejected attach, with its cause code, is the first clue when a device goes silent.

At VoicePro: The network log in our IoT portal shows attaches, rejections and empty sessions.

An operator switching off an old network generation, such as 3G, to reuse its spectrum. Devices that only support that generation stop working, so IoT fleets plan replacements years ahead.

Removing a lock that ties a phone to one network. Since December 2021 UK providers may not sell locked phones.

The UK Network and Information Systems Regulations 2018, which set security and incident reporting duties for essential services and some digital providers.

A number not tied to a place, such as UK 03, 08 and 09 numbers. Calls are routed wherever the owner chooses.

New Radio. The 5G radio standard defined by 3GPP. NR bands are written with an n, such as n78.

The regulator granting a block of numbers to a communications provider. In the UK Ofcom allocates numbers, usually in blocks of 1,000 or 10,000.

A provider keeping a number on its network and routing its calls for a customer, whoever originally owned the range.

Connecting two parties through a temporary number so neither sees the other's real number, as used by taxi and delivery apps.

The right to keep your phone number when you change provider, for both mobile and landline numbers.

Checking that a number falls inside a range the regulator has actually allocated, and to whom. A call from an unallocated range is invalid and often fraudulent.

At VoicePro: VPX Global Insight+ runs number range checks (VPX-NRV).

What kind of line a number belongs to: mobile, fixed, freephone, premium, VoIP or pager. It affects cost, routing and fraud risk.

A country's rules for how its numbers are structured and used. The UK National Telephone Numbering Plan is published by Ofcom.

The Office of Communications. The UK regulator for telecoms, broadcasting, spectrum and post. It sets the General Conditions providers must follow and allocates phone numbers.

The UK process for switching broadband and landline provider in which the new provider handles everything, without the customer having to contact the old one.

Online Charging System. Checks and deducts balance in real time while a call or data session is in progress, so a prepaid user cannot go below zero.

A recipient asking not to receive further marketing texts, usually by replying STOP. UK law requires an easy free way to opt out of marketing messages.

An open, flexible audio codec used by WebRTC and many apps. It adapts its bitrate to the connection and gives high quality at low bandwidth.

Receiving calls into a network, for example on a phone number, and delivering them to a customer. The opposite of termination.

Over-the-air. Managing a SIM remotely over the mobile network, without touching the device: updating its settings, adding services or downloading an eSIM profile.

One-Time Password (or passcode). A short code sent by SMS, app or email that is valid once and for a few minutes, used to confirm sign-in or a payment.

Charges for usage beyond what a plan includes, such as calls to excluded numbers or data after the allowance runs out.

A SIP header that carries the verified identity of the caller between trusted networks, separate from the number shown to the person called.

Person-to-Person SMS. Ordinary texts between people.

Porting Authorisation Code. The code that lets you keep your mobile number when you switch provider. In the UK, text PAC to 65075 to get it by text straight away; your new provider uses it to move your number, usually within one working day.

Voice packets that never arrive. Even 1 to 2 percent can cause clipped or robotic audio.

A business that resells mobile or eSIM services to its own customers, usually through an API or a white-label platform.

A sign-in method that replaces passwords with a cryptographic key stored on your device and unlocked by fingerprint, face or PIN. It cannot be phished or reused on fake sites.

A prepaid service where you top up credit and pay only for what you use, with no monthly contract.

Private Branch Exchange. A business phone system that connects internal extensions and shares a set of outside lines.

Breaking into a business phone system, often through weak passwords, to make expensive calls at the owner's cost, typically over a weekend.

At VoicePro: Our cloud phone system has fraud protection built in.

Payment Card Industry Data Security Standard. Security rules for any business that stores, processes or transmits card details.

Post Dial Delay. The time between finishing dialling and hearing ringing. A key quality measure for voice routes; long PDD makes callers hang up.

A data session between a device and the network, set up through an APN. A device can be attached but have no session, in which case it cannot send data.

Privacy and Electronic Communications Regulations 2003. UK rules on marketing calls, texts and emails, cookies and the privacy of communications. Most marketing texts and emails need prior consent.

Two networks connecting directly to exchange traffic between their customers, often without payment. Used for both IP data and voice.

Charging for the exact data used, by the megabyte, instead of a fixed bundle.

At VoicePro: Our IoT data is billed per megabyte, with no bundles to pre-buy.

Using a foreign SIM in a country long term instead of just visiting. Many networks restrict it in roaming agreements, and some countries limit it by law.

Tricking people into revealing passwords, codes or payment details through fake messages or websites. Smishing uses SMS; vishing uses voice calls.

Goods and services charged to a phone bill, such as premium rate calls and texts. Ofcom regulates them directly since taking over from the PSA in 2025.

The 4 to 8-digit code that locks your SIM so it cannot be used in another phone. After three wrong attempts the SIM locks and needs the PUK.

The VAT rule that decides which country's VAT applies to a sale. For telecoms supplied to consumers it is generally where the customer belongs.

Public Land Mobile Network. Any public mobile network, identified by its MCC and MNC.

The record of when and between which networks a number has been ported. A very recent port can be a sign of SIM swap or port-out fraud.

At VoicePro: VPX Global Insight+ returns port history and last port.

A criminal requesting a PAC in the victim's name to move their number to a SIM they control, then using it to receive security codes.

Moving a number from one provider to another. Mobile ports in the UK use a PAC; landline and business number ports usually need an LOA.

Paying after use: the service runs first and is billed at the end of the period, usually needing a credit check. Also called postpaid or contract billing.

Paying before use: you buy credit or a plan in advance and service stops or slows when it runs out. Also called prepaid.

A record of customers who need extra support, for example because of disability or illness. UK providers must have policies to identify and support vulnerable customers.

An APN dedicated to one customer, keeping device traffic off the public internet and inside a private network, often with fixed IP addresses.

An eSIM profile is a mobile plan as stored on an eSIM: the network credentials and settings that let a device connect. One eSIM can hold several profiles.

Some countries require local address or ID before a geographic number can be issued, which can delay activation.

Charging or crediting a part-period when a plan starts, changes or ends mid-cycle, in proportion to the days used.

Power Saving Mode. Lets an IoT device switch its radio off for long periods while staying registered, so it can wake and send data without reconnecting from scratch.

Public Switched Telephone Network. The worldwide traditional phone network. In the UK the copper PSTN is being switched off as calls move to digital, IP-based services.

PIN Unblocking Key. An 8-digit code that unlocks your SIM after three wrong PIN attempts. Ten wrong PUK attempts block the SIM permanently, so contact support if you are unsure.

Installing an eSIM by scanning a QR code that holds the SM-DP+ address and activation code. The phone then downloads the profile.

At VoicePro: Travel eSIMs arrive as a QR code by email as soon as you pay.

Radio Access Network. The masts, antennas and base stations that connect phones to the core network over radio.

The provider a number block was originally allocated to by the regulator. Ported numbers still show the original range holder in allocation data.

A carrier's price list: every destination and dial code with its rate, billing increment and effective date. Also called a rate table or rate sheet.

At VoicePro: VPX Carrier Voice delivers rate tables by REST API or flat file.

Notice from a carrier of new rates with an effective date. Increases normally carry a notice period agreed in the contract; decreases may apply at once.

Working out the price of each usage record, such as a call or data session, from the tariff that applies to it.

Rich Communication Services. The upgrade to SMS that adds read receipts, typing indicators, high-quality media and branded business messages, delivered over mobile data.

Pricing and deducting usage as it happens rather than at the end of a billing period, so balances and spend caps are always current.

Automatically charging a customer at regular intervals for a subscription, usually by card or Direct Debit.

Money returned to a customer for a payment, in full or in part, usually to the original payment method.

The UK text relay service that lets deaf people and people with speech difficulties make and receive phone calls through a relay assistant. Providers must give access to it.

A VAT rule for many business-to-business services bought from abroad, where the buyer, not the seller, accounts for the VAT. Common in wholesale telecoms.

Roam Like at Home. The EU rule that lets EU customers use their home allowance in other EU countries at no extra charge. Since Brexit it no longer binds UK providers, which set their own European roaming terms.

Using your mobile service on another operator's network, usually abroad. Your home network pays the visited network and passes on the cost under your plan's roaming terms.

At VoicePro: Travel eSIMs give you local data abroad without a roaming bill.

The path and supplier a call takes to reach its destination. A destination often has several routes with different costs and quality.

Placing real test calls over a route to check connection, CLI delivery, audio quality and correct answer signalling before sending live traffic.

Remote SIM Provisioning. The GSMA standard for downloading, enabling, disabling and deleting eSIM profiles remotely and securely.

Reference Signal Received Power. The standard measure of 4G and 5G signal strength, in dBm. Around -80 is strong; below -110 is weak.

RTP Control Protocol. Runs alongside RTP and reports call quality statistics such as packet loss and jitter.

Real-time Transport Protocol. Carries the actual voice and video packets of a VoIP call, while SIP handles setting the call up.

Checking customers and payments against government sanctions lists before providing service, as UK law requires.

Session Border Controller. A network device or software that sits at the edge of a VoIP network to protect it, translate between different SIP setups, handle NAT and enforce call limits.

Session Description Protocol. The part of a SIP message that lists the media details of a call: addresses, ports and codecs on offer.

Tamper-resistant hardware in a device or SIM that stores keys and sensitive data, protected against physical and software attacks. Every eUICC is built on one.

What appears as the sender of a text: a phone number, short code or brand name.

Registering a brand sender name with networks or regulators before use. Many countries require it to fight fraud; unregistered names may be blocked or replaced.

At VoicePro: VPX Carrier SMS manages sender ID registration across 50+ markets.

Paying what carriers owe each other for the traffic exchanged, on agreed terms and currency.

At VoicePro: VPX Carrier Voice settles in GBP, USD and EUR.

The original GSMA eSIM specification for M2M, where the operator pushes profiles to devices through an SM-SR server.

At VoicePro: VPX eSIM Connect+ supports SGP.02 M2M profiles.

The GSMA specification for consumer eSIM: how phones, tablets and watches download and manage profiles, usually by QR code.

At VoicePro: VPX eSIM Connect+ provisions SGP.22 consumer eSIM profiles over the air.

The newer GSMA eSIM specification for IoT. It brings consumer-style eSIM flexibility to devices without screens, through the eIM and IPA, making it easier to change network over the air.

A 5 or 6-digit number used for high-volume texts such as votes, competitions and alerts. Short codes are country-specific.

Calls lasting only a few seconds, typical of diallers, surveys and voice broadcasts. Many carriers penalise them with surcharges.

A network defence that filters SS7, Diameter and 5G signalling messages to block location tracking, interception and fraud attempts from rogue networks.

Subscriber Identity Module. The card or embedded chip that identifies you to a mobile network and holds the keys used to authenticate and encrypt your connection.

Equipment holding many SIMs that turns international calls into local mobile calls, bypassing interconnect fees. It degrades quality and hides the real caller ID.

The stages an IoT SIM moves through, such as ready, test, active, suspended and terminated, each with its own billing.

A criminal persuading a mobile provider to move a victim's number to a new SIM, then using it to receive one-time codes and break into bank and email accounts. Providers defend with identity checks and by flagging recent swaps to banks.

A mobile plan sold without a phone. You use your own handset, usually on a shorter contract or rolling monthly.

Session Initiation Protocol. The main signalling protocol for VoIP, used to start, change and end calls. Its default port is 5060 (5061 over TLS).

At VoicePro: VPX Carrier Voice interconnects over SIP (RFC 3261).

The SIP request that starts a call. It carries who is calling whom and, in its SDP, how the media should flow.

SIP signalling sent over an encrypted TLS connection, usually on port 5061, so call details cannot be read or altered in transit.

How a phone or PBX tells a SIP server where it can be reached, by sending a REGISTER request with its credentials at regular intervals.

Three-digit replies in SIP, grouped like web codes: 1xx progress (180 Ringing), 2xx success (200 OK), 4xx request errors (404 Not Found, 486 Busy Here), 5xx server errors and 6xx global failures.

A virtual phone line delivered over the internet or a private link, connecting a phone system to the public phone network. It replaces ISDN and analogue lines.

A SIP address in a form like sip:user@domain, used to route calls directly over IP without a phone number.

In DPoS blockchains, the penalty mechanism for validators who behave dishonestly or go offline during their assigned block production slot. Slashed stake is typically burned or redistributed.

Subscription Manager Data Preparation. The secure server that prepares and delivers eSIM profiles. The SM-DP+ address and activation code in an eSIM QR code tell your phone where to download your profile.

Subscription Manager Discovery Server. A GSMA service that tells a device an eSIM profile is waiting for it, so it can be downloaded without scanning a QR code.

A low-power base station covering a small area such as a building or street, used to add capacity or fill coverage gaps.

Phishing by text message, such as fake parcel or bank alerts with a link to a fraudulent site. In the UK you can forward suspected scam texts free to 7726.

Short Message Peer-to-Peer. The standard protocol for exchanging SMS between carriers, aggregators and message centres, usually version 3.4 over TCP.

At VoicePro: VPX Carrier SMS connects over SMPP v3.4.

Short Message Service. Plain text messages of up to 160 characters per segment, sent through the mobile network and readable on any phone.

A network system that inspects incoming texts and blocks spam, fraud and unpaid grey-route A2P traffic.

Delivering business texts through channels meant for personal messages, such as SIM farms, to avoid A2P fees. Deliverability and sender ID suffer and networks block it.

Short Message Service Centre. The network system that stores texts and forwards them to the recipient's phone, retrying if it is switched off.

A phone app on a computer or mobile that makes calls over the internet as an extension of a phone system.

Software that routes calls between networks, replacing hardware exchanges. Class 4 softswitches route traffic between carriers; Class 5 serve end users with features such as voicemail.

The radio frequencies mobile networks transmit on. In the UK Ofcom licenses it, usually by auction. Low bands travel further; high bands carry more data.

A limit you set on how much can be charged beyond your plan in a month. UK mobile providers must offer customers the option of a cap.

Service Provider Name. The network name shown at the top of your phone screen.

Buying and selling wholesale routes at short notice at current prices, rather than on long-term committed deals.

Secure Real-time Transport Protocol. The encrypted version of RTP, so call audio cannot be listened to in transit.

Signalling System No. 7. The decades-old signalling network that phone and mobile operators use to set up calls, send texts and support roaming. SIGTRAN carries it over IP.

Abusing the trust built into the SS7 signalling network to track a phone's location or intercept texts. Signalling firewalls defend against it.

Service Termination Authorisation Code. The UK code for leaving a mobile provider without keeping your number. Text STAC to 75075 to get it.

A fixed IP address assigned to a device so a server can always reach it, usually on a private APN.

A home network directing roaming devices onto preferred partner networks, usually for commercial reasons, even when another network has better signal.

At VoicePro: Our IoT SIMs carry no preferred list: the device attaches to the strongest network in range.

Secure Telephone Identity Revisited and Signature-based Handling of Asserted information using toKENs. A framework in which the originating network digitally signs the caller ID so the receiving network can check it was not spoofed. Mandatory in the US and Canada.

The UK and EU rule that most electronic payments must be confirmed with two of: something you know, something you have, something you are.

The standard for sending fax over IP networks. Fax sent as ordinary audio over VoIP often fails, so T.38 relays it as data instead.

The set of prices that applies to a service, such as a plan's monthly charge and its rates for anything outside the allowance.

Time Division Multiplexing. The circuit-switched technology of the traditional phone network, where each call has a fixed channel. Largely replaced by IP.

Telephony Denial of Service. Flooding a phone number or contact centre with calls so real callers cannot get through.

At VoicePro: VPX Numbering includes always-on TDoS protection.

The UK law that places strong security duties on public telecom providers, backed by the Telecommunications Security Code of Practice and Ofcom enforcement.

Collecting and sending data from vehicles, such as location, speed, fuel and driver behaviour, over mobile networks.

Delivering a call to its final destination network. Wholesale termination is selling that delivery to other carriers and platforms.

At VoicePro: VPX Carrier Voice sells wholesale termination to 200+ countries.

The UK process, introduced by Ofcom in July 2019, for getting a PAC or STAC by free text in seconds, along with any early exit charges you would owe.

Deliberately slowing a connection, for example after a data allowance or fair use limit is reached.

A large carrier with its own international network that reaches every other network directly or by settlement-free peering, without buying transit.

A number that is free for callers to dial, paid for by the receiving business. UK 0800 and 0808, US 800 and similar.

At VoicePro: VPX Numbering covers toll-free ranges as well as local and national numbers.

Adding credit or extra allowance to a prepaid account or plan.

Telephone Preference Service. The UK register of people who have opted out of unsolicited sales and marketing calls. Businesses must screen against it before making live marketing calls.

The calls, messages or data passing over a network, measured in minutes, messages or bytes.

Converting a call from one codec to another in the network when the two ends do not share one. It adds delay and cost, so it is avoided where possible.

Carrying traffic across your network between two other networks, neither of which is your own customer.

Texting where recipients can reply to the business, using a long code or short code rather than a name-only sender ID.

Unified Communications as a Service. Cloud-hosted calling, voicemail, messaging and video in one subscription service.

At VoicePro: Our cloud phone system brings numbers, calls and devices onto one bill.

The SMS encoding used for characters outside GSM-7, such as Arabic, Hindi, Bengali, Urdu or emoji. One segment holds 70 characters.

Unified Data Management. The 5G core function that holds subscriber data and credentials, replacing the HSS.

Universal Integrated Circuit Card. The technical name for the smart card inside a SIM. The eUICC is its embedded, remotely managed version.

Universal International Freephone Number. A single freephone number, +800 followed by eight digits, that works in every participating country.

A roaming SIM with no preferred network list, so the device picks the strongest available network itself.

Charges based on how much of a service was used, such as minutes, messages or megabytes, as opposed to a fixed monthly fee.

Unstructured Supplementary Service Data. Short codes starting with * and ending with #, such as a balance check code, that open a live session with the network for balances, menus and settings.

A memorable number, such as one with repeating digits. Some providers charge extra for them.

Value Added Tax. The UK standard rate is 20 percent. Consumer prices must be shown including VAT; business prices are often quoted excluding it.

One Stop Shop. The EU scheme that lets a business selling telecom and digital services to consumers in several EU countries declare and pay all their VAT through one return, instead of registering in each country.

A number not tied to a physical line or SIM. Calls to it are forwarded to any phone, app or system over IP.

At VoicePro: VPX Numbering activates virtual numbers on purchase through the portal.

Voice phishing: scam calls that impersonate banks, police or tech support to obtain money or details. Often combined with CLI spoofing.

Visitor Location Register. A temporary database of the subscribers currently in an area of a 2G or 3G network, including visiting roamers.

Delivering voicemail messages to an inbox as audio files, often with a text transcription.

At VoicePro: Our cloud phone system sends transcribed voicemail to email.

Voice over IP. Voice calls carried over internet protocol networks instead of the traditional phone network.

Voice over LTE. Calls carried over the 4G network instead of older 2G and 3G, giving clearer audio, faster call set-up and data during calls.

Voice over New Radio. Calls carried natively over 5G standalone networks, the 5G successor to VoLTE.

The blockchain foundation of the VPX Ecosystem. Provides an immutable ledger for routing events, fraud records, quality data and settlement transactions, secured by Mysticeti-class DAG-BFT consensus. In development; mainnet planned mid-2027.

The native utility token of the VPX Ecosystem. Used for staking, governance voting, node operator rewards, carrier fee discounts and consumer rewards. Fixed supply of 1 billion tokens. References to £0.10 / $0.10 per VPXN in whitepaper documents are illustrative examples for economic modelling purposes only.

Japanese for "one ring and cut". Fraudsters ring numbers once from premium-rate international numbers, hoping people call back and pay high charges.

At VoicePro: VPX Global Insight+ blocks Wangiri callbacks.

Web Real-Time Communication. Built into modern browsers, it lets web pages make encrypted voice and video calls without plug-ins.

Selling call carriage to other telecom companies in bulk, priced per minute by destination, rather than to end users.

Making and receiving normal mobile calls and texts over Wi-Fi when mobile signal is weak, using your usual number (also called VoWiFi).

A call where the caller has chosen not to show their number. The network still knows it and passes it to emergency services.

A security approach where no user or device is trusted by default, even inside the network: every access is verified each time.