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21CV change over VOIP app

Joining in

I'm being changed to the new 21CV adapter this week (due to a line fault on the existing line) - given this is now a VOIP service, is there a mobile app I can use to connect to it on top of the phones plugged in to the router adapter?


Forum Team (Retired)
Forum Team (Retired)

Hi LaurieC, 


Thank you for your post and welcome to the forums. 


There isn't an app which comes with the new VOIP service - any questions and all information relating to the changeover can be found through this link here:





I didn't ask if you provided an app, but if we are able to use the VOIP service from an app (or other device)?  It looks like the router is acting as a VOIP client and end-point for a standard service, which in. theory means we should be able to use other standard clients.  I not, it seems a big missed opportunity to allow greater flexibility for your clients, and as it's a form of VOIP service then I might just port the number to someone who can if it's not supported.

Hi LaurieC,


No, you cannot use the service from an app or another device.


The switch is to connect the landline to the hub inline with the government objective.


This has to be completed by 2025, we are choosing to take the change over now to ensure all of our customers have been migrated prior to the current telephone exchange being closed down in 2025.


Thank you for your feedback and suggestion. If this is something we offer in the future we will update our website and the forums.

Vikki - Forum Team

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Very Insightful Person
Very Insightful Person

Please note the 21CV is not a real VOIP system and does not have all the ‘bells and whistles’ that a full VOIP system implements. It’s just a way of getting rid of the old POTS telephone.

There are 10 types of people: those who understand binary and those who don't and F people out of 10 who do not understand hexadecimal c1a2a285948293859940d9a49385a2

Up to speed

The way I look at it is this.

PSTN is designed for electrically passive POTS phones. The exchange sends a ringing tone when there is an incoming call, and enables outgoing calls by supplying a dial tone when it detects the receiver being off-hook.  The subscriber number is hard-wired at the exchange.

With VOIP, the phone itself is smart - it responds to incoming calls destined for the device itself over the network, and contacts the network when the subscriber calls a number.  Mobile phones these days are VOIP devices since they will use an internet connection if available over Wi-Fi.

21CV / Digital Voice simply moves the functions required to use a POTS phone from the exchange to the hub, which handles the digital connection to the network - i.e. it's just PSTN with a very short "exchange" line.