BT Digital Voice and mobile phone

David Higton

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Sep 14, 2021, 2:54:51 PM9/14/21

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BT's transition to Digital Voice must be quite close now. OK, it's
going to be VoIP, so I thought it would be relatively easy to connect
my mobile phone (with a VoIP app) to the service so I could answer
incoming calls on the mobile. (I'm not interested in making outgoing
calls via BT.)

Not so easy, from what I read. Their VoIP is so tightly screwed down
that it will be almost impossible to get a direct connection from
anything other than their hub, it seems. I read of one person who
reverse engineered how to do it, but it seems too difficult to be
reasonably attempted.

If only there were a VoIP UA in the hub that other devices could connect
to.

Failing that, the only method seems to be to take the phone output
from the hub and convert that to VoIP using an FXO gateway. But even
that is difficult - all the low cost single channel products have been
discontinued, it seems.

Any creative solutions? Something I've missed?

David

David Woolley

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Sep 14, 2021, 6:52:01 PM9/14/21

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On 14/09/2021 19:54, David Higton wrote:
> BT's transition to Digital Voice must be quite close now

BT's voice service has been digital for all but the last mile and then
only for small businesses and domestic users, for several decades now.
As mentioned in another thread, even small businesses had a digital
voice option, to the premises, several decades ago, although it was
generally only people who wanted data as well that used it.

All links down to the remote concentrator level (exchange buildings)
have been digital and business user with multiple lines and a PABX will
generally have been connected using digital.

All BT phone calls are handled as digital at some part in their journey.

Theo

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Sep 14, 2021, 6:52:54 PM9/14/21

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David Higton <da...@davehigton.me.uk> wrote:
> Not so easy, from what I read. Their VoIP is so tightly screwed down
> that it will be almost impossible to get a direct connection from
> anything other than their hub, it seems. I read of one person who
> reverse engineered how to do it, but it seems too difficult to be
> reasonably attempted.

Do you have a link to that? I did a bit of reverse engineering of Sky's
equivalent, and would be interested to know how it compares.

> If only there were a VoIP UA in the hub that other devices could connect
> to.

There's a big hassle if you want to use your own router too...

> Failing that, the only method seems to be to take the phone output
> from the hub and convert that to VoIP using an FXO gateway. But even
> that is difficult - all the low cost single channel products have been
> discontinued, it seems.

The good old SPA3102 is on ebay for about £35+VAT from China:

https://www.aliexpress.com/item/1005003168255627.html

(I'm not sure why they seem to only exist in China these days. Cisco claim
they're out of support and haven't been manufactured since 2015)

You can also get FXO modules for the Pi if you want to cook up your own
Asterisk setup:
https://switchpi.com/

Theo

Theo

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Sep 14, 2021, 6:59:09 PM9/14/21

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David Woolley <da...@ex.djwhome.demon.invalid> wrote:
> On 14/09/2021 19:54, David Higton wrote:
> > BT's transition to Digital Voice must be quite close now
>
> BT's voice service has been digital for all but the last mile and then
> only for small businesses and domestic users, for several decades now.
> As mentioned in another thread, even small businesses had a digital
> voice option, to the premises, several decades ago, although it was
> generally only people who wanted data as well that used it.

'BT Digital Voice' is their marketing for their residential VOIP product,
which is almost certainly SIP under the hood. 'Cloud Voice' is one of their
business VOIP products.

It's the specific implementation of their SIP product that is relevant here.
Knowing that ISDN was digital is not conducive to getting your phone working
with this new product.

Theo

notya...@gmail.com

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Sep 16, 2021, 8:06:18 AM9/16/21

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BT provided BT Broadband Voice (business) and BT Broadband Talk (residential) for many years. You got a landline number and for the business number a cap on call costs (5p landline, 20p mobile), which was useful if yo knew you would be making a long call, but more expensive if you made lots of short calls. Residential got free weekend calls. Both services were normally inclusive.

These were implemented as VOIP and typically accessed using BT's soft phone on one's PC, although some hubs had an optional DECT handset.

You could easily intercept the set up string because BT did it by embedding the server, username and password in the URL of the web page they used to enable to the soft phone - so simple cut and paste.

These could then be programmed into a Voip phone (e.g. Gigaset) or even a suitable mobile connected by Wi-Fi to the BT hub. OTOH the connection would only work on the hub concerned and registration would be lost once the PC was switched off.

A few to several years ago BT discontinued their VOIP products. The numbers were ceased and BT flat refused to port them out, although anticipating this from the start I had been careful not to distribute them.

If you really want to be able to field landline calls native on your mobile then port your BT number(s) out to Voipfone and set up internet calling in your mobile. Been doing it since 2009.