Carrier pre select (CPS) is a fixed-line phone setup that automatically routes chosen types of calls through a provider you picked in advance – with no dialing prefix and no special equipment. You keep your existing line, but your selected calls travel over a different carrier’s network.
You probably landed here after spotting the term on an old contract, a BT line record, or an invoice – or while researching how UK phone competition used to work. This guide explains what CPS is, how it works, how it compares to related services, and why it’s now fading out.
One quick note before we start: this is general educational information about a largely legacy telecom service. It isn’t legal advice or telecom purchasing advice. For your own account, check with your current provider.
What Is Carrier Pre Select? A Plain-English Definition
Carrier pre-selection is a mechanism that lets a phone customer choose, in advance, an alternative provider to carry some or all of their calls – without dialing a code or installing kit. Your line rental stays with one operator, historically BT, while your selected calls route through a carrier you picked.
That definition matches the regulator’s own wording. As Ofcom explains, CPS allows consumers who have a BT line to select, in advance, alternative communications providers to carry some or all of their telephone calls without having to dial a prefix.
The no-prefix, no-equipment part is what made CPS appealing. Older “dial-around” indirect access made you punch in a code before every call. CPS did the routing for you.
Imagine a UK business in the mid-2000s. It keeps its trusty BT line for reliability but sends every international call through a cheaper carrier automatically. Staff dial normally; the savings happen in the background.
CPS is an industry and regulatory term, not a single statute. In the UK it sat under Ofcom’s conditions on operators with significant market power.
How Carrier Pre-Selection Works
CPS works by pre-programming your local telephone exchange to hand off your selected calls to your chosen carrier’s network. The setup lives in the network, not in your office.
Here’s the flow in plain steps:
- You dial a number as normal from your phone.
- The call travels over the incumbent’s local loop (the copper line) to the exchange.
- At the exchange, it’s rerouted to your chosen carrier, who carries and bills it.
You also picked which calls to divert. This is call-type selection. The customer subscribes to one or more alternative providers and chooses the type of calls – for example, all national calls – that will be routed through that provider’s network. You could apply CPS to national, international, or mobile calls, or to all outbound calls, based on where your bill hurt most.
The business reason behind all this was least-cost routing (LCR) – sending each call the cheapest way without reprogramming a PBX.
A common mistake worth clearing up: some people think CPS meant dialing a special code each time. It didn’t. Automatic routing was the whole point.
Read Also: A look at TEK-102
Carrier Pre Select vs Local Loop Unbundling vs Wholesale Line Rental
All three let rivals compete using the incumbent’s network, but they differ in scope, control, and cost to roll out. CPS handles calls, WLR handles the whole line as a resold product, and LLU hands physical control of the line to a competitor.
| Method | What It Covers | Who Controls the Line | Equipment Needed | Typical Use |
|---|---|---|---|---|
| Carrier Pre-Selection (CPS) | Selected calls only | Incumbent (e.g. BT) | None in the exchange | Cut call costs, keep existing line |
| Wholesale Line Rental (WLR) | Line rental + calls, resold | Incumbent, resold by rival | None; a wholesale product | One combined bill from an alternative provider |
| Local Loop Unbundling (LLU) | Line + broadband | Competitor’s own kit | Competitor gear in the exchange | Full-service broadband and voice |
CPS was cheaper and simpler to deploy than LLU because rivals installed no equipment inside the exchange. But it was more limited – usually voice only, and the incumbent kept the line-rental revenue.
WLR sat in between. Providers took lines on wholesale terms from BT and resold them to customers, giving a single bill covering both line rental and calls provided using carrier pre-selection, which was a significant stage in the development of UK retail competition. For deeper background, general references like Wikipedia’s “Carrier preselect” entry cover the international picture too.
Why Carrier Pre Select Mattered (and Who Used It)
CPS mattered because it opened up phone-call competition, letting customers cut their bills while keeping the line they already had. That was a big deal when one operator dominated fixed lines.
Regulators drove it. Operators with significant market power were required to enable CPS so rivals could compete. In the UK, Ofcom determined that BT had significant market power in various narrowband wholesale markets and imposed conditions on BT, including a requirement to provide CPS under SMP Condition AA8. Ireland’s regulator, ComReg, adopted similar measures.
Who actually used it? Businesses with high call volumes, resellers building their own call packages, and cost-conscious households.
Picture a small accountancy firm in 2007. It routes all calls through a discount carrier and trims its monthly bill, while BT still maintains the physical line and fixes faults. Same phones, same number, lower cost.
One detail most consumer explainers miss: CPS turned up often in real disputes – over switching, “slamming” (having your calls moved without clear consent), mis-selling, and billing errors. If your calls suddenly shifted carriers without a proper agreement, that was a CPS problem.
Is Carrier Pre Select Still Used Today?
Carrier pre select is now largely legacy, being wound down as the UK’s copper phone network moves to internet-based (VoIP) services. New sign-ups have dried up, and the underlying network is being retired.
The big driver is the PSTN switch-off. By January 2027, UK landline services will switch to a fully digital network, and the existing Public Switched Telephone Network (PSTN) will be withdrawn. According to the House of Commons Library briefing, the industry had originally targeted a switch-off date of 31 December 2025 before it was pushed back. A national stop-sell on new analogue lines has been in place since September 2023, so ordering fresh CPS-style services largely stopped years ago.
Momentum is real. Ofcom reports the number of landline customers on the PSTN fell from 5.2 million in July 2024 to 3.2 million in July 2025.
With VoIP and digital voice, provider choice and call routing work differently, so traditional CPS obligations are being withdrawn. Ofcom has noted these products are now mature and the old functional rules may hold back newer services.
If you still see CPS on an account, it usually means an older line that’s due for migration. Check with your current provider about moving to a digital service.
You may also find old searches like “carrier pre select codes list” or “carrier pre select 1280.” Those relate to activation and routing codes tied to older systems. CPS codes are four-digit codes starting with the digit 8, for example 8xxx. Most are now obsolete.
Read Also: Understanding TransDS
What To Do Next
If CPS shows up on your paperwork, treat it as a signal, not a to-do: your line is legacy tech heading for the 2027 switch-off, and the real task is planning your move to a digital service.
Do one thing today – call your current provider, confirm whether the line still relies on the PSTN, and ask about your migration path to VoIP or full fibre. Sorting it early beats a rushed cutover later.
FAQ
What is carrier pre select?
Carrier pre select is a fixed-line service that automatically sends chosen call types through a provider you picked in advance, without dialing a prefix. You keep your existing line while a different carrier handles the selected calls.
What does CPS stand for in telecoms?
CPS stands for carrier pre-selection. It’s the industry shorthand for pre-choosing an alternative provider to carry some or all of your calls.
Is carrier pre-selection the same as local loop unbundling?
No. CPS only affects selected calls and needs no competitor equipment in the exchange. Local loop unbundling (LLU) hands physical control of the line to a rival using their own kit. See the comparison table above for the full picture.
Do I still need to dial a prefix with carrier pre select?
No. The whole point of CPS was automatic routing. Unlike older indirect-access “dial-around” services that made you enter a code before each call, CPS was set up once at the exchange and worked in the background.
Is carrier pre-selection still available in the UK?
Not really. CPS is legacy and being wound down. The UK’s copper PSTN will be permanently switched off on 31 January 2027, and a national stop-sell on new analogue lines has applied since September 2023.
What are carrier pre select codes?
These were short activation and routing codes tied to older CPS systems. CPS codes are four-digit codes starting with the digit 8, such as 8xxx. They’re largely obsolete as digital voice takes over.
Who regulated carrier pre-selection?
In the UK, Ofcom regulated CPS, imposing obligations on operators with significant market power like BT. In Ireland, the equivalent regulator was Com Reg, which applied similar competition measures.
What replaced carrier pre-selection?
VoIP and digital voice services replaced it. Calls now travel over broadband, and you choose your provider by picking a digital voice or cloud phone package rather than routing calls at a copper exchange.
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