The End of Analogue Phone Lines (Part 2)

By Michael Spalter
February 2021
phones in trash red1

About the author

Michael Spalter

Michael Spalter


Michael Spalter has been a networking technician for over 30 years and has been the CEO DrayTek in the UK since the company’s formation in 1997. He has written and lectured extensively on networking topics. If you’ve an idea for a blog or a topic you’d like explored, please get in touch with us.

Analogue Phone Service in the UK - It's switching off soon

In Part 1 of this article, we covered the 2025 switch of analogue phone lines/service in the UK.  In this, part 2, we are going to look at some of the practical implications that will affect users who still want phone service and how they will migrate to replacement services.

Customer Premises Equipment (CPE)

Currently, most UK DSL users (that's ADSL, VDSL2 or G.FAST) pay a line rental for the line and analogue phone service, and a separate monthly fee for their broadband service. They are commonly from different companies - the line rental from BT and the ISP could be BT, TalkTalk, Sky etc.     Your phone plugs directly into the BT wall socket, and your DSL device (router or modem - the 'CPE') connects alongside it, but they operate completely independently. You can lose broadband service, you can lose phone service or you can lose both.   Once you have a fully digital service, they're carried together.    Although BT will no longer be providing the analogue phone service, you'll still have the line rental as you're still using the copper line for the broadband delivery, and that's the costly part - phone service is revenue generating for them and they're losing that.  It is likely that the line rental cost will be bundled up with the ISP's Internet service so you'll have one less bill at least.

Most ISPs provide a free router with their service currently, however, in most cases, that router does not have VoIP/phone ports. If you still want phone service, the ISP will likely offer to replace your router with one which has a phone socket in order that they can then sell you VoIP services to replace your analogue voice service.  Alternatively, you can buy your own VoIP hardware such as an IP phone, an IP PBX or your own router with VoIP/phone ports. If you buy your own hardware, you then have a choice of any VoIP service provider, and switch when you wish.  Oftel mandates number portability for VoIP services (and it does for landline providers now) so you can move numbers between providers.

VOIP router back

Note that 999 (911/112) emergency service calling is not available from all VoIP providers and would not be available in the case of a power cut unless you have standby power or a UPS.  This is an important difference from an analogue line which still works when your own local power goes off.

Openreach Voip modem11
A simple broadband to phone VoIP adaptor could look like this.  It converts from DSL or fibre to an analogue phone socket, without other Internet services.

I need my phone... I don't want Internet!

For subscribers who currently have telephone service but no Internet and want to keep it that way - i.e. they don't want or need any fixed Internet connectivity, their telco will provide a DSL modem or fibre ONU (the equivalent of a modem for fibre lines) which has a phone socket on it.   That phone socket will provide voice services using VoIP.    For these customers, the ISP may choose to provide a complete data/Wi-Fi capable router, with the data/Internet connectivity disabled.  In that way, Internet service can easily be switched on later.   Where your provider does provide voice-only service, without Internet, you are tied to using their service for voice calls - you cannot use a 3rd arty VoIP provider as that would require an Internet connection.


BT Home Phones
BT's Digital Home Phone

BT Digital Voice

For users happy to embrace change and 'dump' their existing phones, telcos can use the Internet connection to connect a new DECT cordless base.  BT's Digital Voice service uses one or more DECT handsets - the Digital Home Phone (pictured right). It connects to BT's latest Smart Hub 2 router which has a DECT base already built-in. The BT Digital Home Phone service does not work with other routers, other provider's devices or ISPs other than BT. That is important to note: Unless your Internet ISP is BT, if you currently use BT for your line rental and analogue voice service, you will lose your voice service unless you ISP provides a replacement service or you provide your own via a 3rd party.   Other ISP's routers could provide a similar DECT service.

Unlike cordless phone bases which connect to analogue services, a pure digital/IP system allows you to make several calls at once, a distinct advantage over analogue lines.  That can be different calls from each handset or a conference call to multiple recipients from one handset. BT's Digital Voice service also include, at no extra cost, Caller ID, Call Waiting, Call Protect, Call diversion and Voicemail (like BT's current 1571 service). Many of those cost up to 5.50 each on analogue lines currently.  Other operators are likely to have equivalent services and hardware products or you can buy your own router with VoIP features and then select any VoIP service provider you like (and switch when you wish).  BT's promotional material claims "Digital Voice provides the same reliability, trust and crystal clear calling".  That's a bold claim - unless they are applying QoS (see later) your voice calls are competing with all other household Internet as well as congestion onward on the Internet.   BT have a page on Digital Voice here.

Wired phone extensions around your home or office

Most people who still use analogue phone lines will have multiple extension sockets around their home. Even if they mostly use cordless phone, they will want the cordless base located somewhere for best coverage, access to the voicemail and where they can conveniently put the handset back on to charge.  That may well not be be the same location as where your broadband router with phone port will be located, particularly as a broadband CPE works best on the 'master socket' - the first point of entry into your house.  Whereas previous VoIP adopters did so by choice, and either accepted the loss of physical extensions, didn't need analogue phones or worked out their own way of wiring them in, this will have to be made much easier for  'the masses'. 

To enable subscribers to more easily connect their existing extension wiring into their router's VoIP/phone ports BT will be able to provide a replacement faceplate for their NTE5c sockets (your home or office's 'master' socket). You can identify your socket type from BT's page here.  The NTE5c faceplates vary by age. Some provide an RJ-11 socket for your DSL CPE (router/modem) and a BT-type socket for you to connect your telephone into. Older ones just have a BT type socket into which you connect a microfilter which gives the separate RJ-11 and BT sockets.  In the back of the NTE5c faceplate, there are normally pushdown terminals into which you can connect your extension wiring - they are isolated from the line when you remove the faceplate to enable Openreach to test the line more easily.

Openreach's new 'VRI' or 'SOGEA' faceplate (photo below) has an RJ-11 socket for your CPE (modem/router) but then a second RJ-11, coloured green into which you can connect your router's phone 'output' - so that socket becomes an input to the rest of your house wiring.  At the same time, the house wiring beyond the NTE5c is isolated from the 'phone' line outside of the house, in order to avoid you sending your analogue phone signal back up to the network ('Voice ReInjection' - VRI).  BT can detect the type of NTE5c on your line and whether its set to 'narrowband' blocking (i.e. the extensions are properly isolated from the incoming copper) and it can be reported in their diagnostics XML export, though this only works on recent NTE5c faceplates. 

There are two types of SOGEA faceplate: SOGEA 1b and SOGEA 2b (also called VoIP and VoIP-S).  By default, they operate identically - they allow broadband through from the exchange (or street cabinet) and block narrowband (analogue voice) coming from the exchange. The VoIP-S (2b) version has an additional switch which turns off the DSL filter to the socket so that narrowband (analogue voice) from the exchange is not filtered - this is required for MPF services where an analogue voice service is provided externally (see MPF in part one of this article).

NT5C-VRI
Above: This is the new VRI NTE5c "SOGEA Faceplate". The left-hand socket connects to your router's RJ-11 DSL interface. A cable from your router's phone port connects into the RJ-11 socket behind the green flap and feeds the wired extensions around your home.

If you don't have a modern NTE5c socket or otherwise can't get the new faceplate, you can fashion your own solution to connect your house extensions into your router's phone socket but bear in mind the following:

  • Although analogue phones operate on only 2 wires (that's how many come from the exchange), in the UK, some older phones may require 3. That 3rd wire (pin 3) carries the ring current which it gets  by having a 300uF capacitor across pins 2&3 - that pulls off the AC ring current, leaving the DC phone signal alone. You'll normally receive an RJ-11 to 'BT socket' adaptor with your router which should contain the capacitor so you may have to integrate that into your wiring.  Most modern phones will work just fine on 2 pins now as they are built for international markets.

  • The electrical current required to ring the 'bell' on a modern analogue phone is small; cordless phones even smaller as the current only needs to be detected, not actually drive bell or ringer however, if you have several extensions, you have to ensure that your router has enough power to ring all of them. Phone ring current should be 48VAC.  Most routers operate on low voltage DC so they have to internally generate something near enough to 48VAC with enough current to ring a typical phone. Modern phones need little current and are very tolerant on voltage levels, but with several extensions, there may be a problem. 20+ years ago, when more phones had mechanical ringers, even a regular phone line might need boosting sometimes and there were products called REN Boosters.   REN (Ringer Equivalency Number) was the measurement of how much current a phone needed to ring. An analogue phone line was rated to support up to 4 REN and a phone can require anything from 0.5 to 2 REN to ring.

A&A, an ISP, provide instructions on how to modify an existing NTE5c faceplate so that the phone socket converts from an 'output' (for a phone) into an 'input' for injection of your VoIP signal into your extensions but it does require modifying the circuit board so you need to be confident that you know what you're doing and I've no idea if it's officially allowed by Openreach.

VOIP to extensions
Above: If you don't have a VoIP insertion faceplate, you can modify your existing home or office wiring so that your router's VoIP phone ports feed your wired extensions. Left is how your existing NTE4 plate feeds your extensions - you can remove that wire and connect it to the router instead. Your wiring may vary so be sure you understand what's going on in your own setup.  Don't add more phones than your router can provide ring current (REN) for.

After analogue switch off, you will no longer need microfilters around your house on each phone extension.

QoS / CoS and Virtual Channels for Voice Calls

You may already be using your broadband line for voice calls, using any variety of VoIP - Skype, WhatsApp, Facetime, Alexa, Google Voice or conferencing such as Teams or Zoom.  Your mobile phone may also fall back to Wi-Fi offloading when you have Wi-Fi connectivity.  You're then subject to competing with all other users in your home or office (TVs, gaming, file transfer etc.) and the reliability or consistency of your call may vary.

The frustration of a poor-quality voice call is common.  People who have analogue phone service need reliable service and won't tolerate the type of quality which we put up with on a contended service. You've probably said to someone "Let me call you back on a landline". From 2025 you won't have a landline anymore. This may be especially worrying for those making or handling emergency services calls.

In order to ensure the Quality of Service (QoS) on a distinct VoIP service - i.e. one which the customer is specifically paying the carrier for compared to one he adds himself, the carrier (service provider/ISP) can use distinct virtual channels on your digital service to separate priority voice signals from regular Internet traffic.  The priority channels will have guaranteed bandwidth back onto the network and be carried within the network with 'Class of Service' flags in order that they are classified as priority. On ADSL, priority channels can be marked with different VPIs (Virtual Path Identifiers), on VDSL2, different VLAN IDs, on cable/DOCSIS it's an SID and on GPON (fibre) it's ALLOC_IDs.  Alternatively, VoIP traffic can be recognised at the IP layer and separating it from regular Internet traffic, sending it over independent routes with guaranteed QoS, however, it would still be contended as it leaves your premises.

Otherwise, your ISP might just put your VoIP service on the same virtual channel as your Internet connectivity and 'hope for the best'.

Number Migration

If you have an analogue phone service, you, of course, have a phone number. I know people who have had the same phone number for 50 years. My grandmother had hers for even longer - it originally, before direct dialling had just 4 digits ("Whitehall 6712 please operator!"), then 7, then it got an area code which over time changed from 01 to 081 to 0181 to 020 but it was still the same number (q.v. Trigger's Broom). People want to keep their numbers, just as you do when you switch mobile carriers so when moving from analogue voice lines to VoIP, the telcos and ISPs will also migrate your number across so, all being well, everything will carry on exactly as before.  BT will only provide their own VoIP service (BT Digital Voice) if they are your Internet ISP or you only have voice service (no Internet) so you will need to use your own ISPs VoIP service or a 3rd party provider (4Com, Vonage, DrayTEL, RingCentral, Telappliant etc.).  Check that the new provider can migrate your existing phone number across - Ofcom do mandate number portability from your current provider.



I hope you've found this article useful. This is a rapidly changing and evolving topic. While researching it, there was a lot of conflicting information, partly due to changes and partly due to other's guesswork so this article and the previous cover what I believe to be correct at the time of writing.  It's an important topic so please do share a link on social and business networks / media and do make any comments below.


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