Recently my fixed line telephone service was switched over from PSTN to digital "21CV" by Virgin
Media. As a result my BT4600 (with built-in TrueCall) no longer works correctly - specifically when
in call blocking mode, rather than asking unknown callers to state their name before the phone
rings, it simply drops the call completely. I do not know whether this issue affects BT's "Digital
Voice" as well.

Is there an updated version of the BT4600 which will work correctly on VM? According to the VM
forum, stand-alone TrueCall units can be tweaked to make them work with VM's "21CV" but I'd prefer
to have a handset with TrueCall built in.

On Wed 10/05/2023 10:47, Codger wrote:
> Recently my fixed line telephone service was switched over from PSTN to digital "21CV" by Virgin
> Media. As a result my BT4600 (with built-in TrueCall) no longer works correctly - specifically when
> in call blocking mode, rather than asking unknown callers to state their name before the phone
> rings, it simply drops the call completely. I do not know whether this issue affects BT's "Digital
> Voice" as well.
>
> Is there an updated version of the BT4600 which will work correctly on VM? According to the VM
> forum, stand-alone TrueCall units can be tweaked to make them work with VM's "21CV" but I'd prefer
> to have a handset with TrueCall built in.

IMSMC VM send the CLI at a different time to other providers viz. BT.
ISTR that BT send the CLI before the first ring whereas VM send it after
the first ring.

We had a BT4600 set (good bar the digital feedback into the analogue
circuits causing and making noise on the line) and I think there was
something in the setup about 'first ring' - you could try that?

On Wed, 10 May 2023 12:04:26 +0100, Woody <harrogate3@ntlworld.com> wrote:

>On Wed 10/05/2023 10:47, Codger wrote:
>> Recently my fixed line telephone service was switched over from PSTN to digital "21CV" by Virgin
>> Media. As a result my BT4600 (with built-in TrueCall) no longer works correctly - specifically when
>> in call blocking mode, rather than asking unknown callers to state their name before the phone
>> rings, it simply drops the call completely. I do not know whether this issue affects BT's "Digital
>> Voice" as well.
>>
>> Is there an updated version of the BT4600 which will work correctly on VM? According to the VM
>> forum, stand-alone TrueCall units can be tweaked to make them work with VM's "21CV" but I'd prefer
>> to have a handset with TrueCall built in.
>
>
>IMSMC VM send the CLI at a different time to other providers viz. BT.
>ISTR that BT send the CLI before the first ring whereas VM send it after
>the first ring.
>
>We had a BT4600 set (good bar the digital feedback into the analogue
>circuits causing and making noise on the line) and I think there was
>something in the setup about 'first ring' - you could try that?
>

The instruction book (pp 70 &71) documents the effect of First Ring = OFF, but is silent about the
effect of First Ring = ON.

So, I tried the ON setting as you recommended, and guess what?

SUCCESS!

Thank you!

On 10/05/2023 12:04, Woody wrote:
> IMSMC VM send the CLI at a different time to other providers viz. BT.
> ISTR that BT send the CLI before the first ring whereas VM send it after
> the first ring.

BT are actually the odd ones out. Their system allows for services to be
delivered without the phone ringing, such as the SMS service.

The after first ring standard is what the Americans did. BT does a line
reversal, before the first ring, to silently signal an incoming call,
and, if I remember correctly, the phone does a, brief, partial loop on
the line, to indicate it wants the caller ID, and also to "wet" the line.

I suspect the timing of the line reversal may be the real problem with
using the wrong mode.

Codger wrote:

> my fixed line telephone service was switched over from PSTN to
> digital "21CV" by Virgin> Media.
Do you still get CLI for incoming calls?

On Wed, 10 May 2023 17:16:46 +0100, Andy Burns <usenet@andyburns.uk> wrote:

>
>Codger wrote:
>
>> my fixed line telephone service was switched over from PSTN to
>> digital "21CV" by Virgin> Media.
>Do you still get CLI for incoming calls?

Yes.

David Woolley <david@ex.djwhome.demon.invalid> wrote:
> On 10/05/2023 12:04, Woody wrote:
> > IMSMC VM send the CLI at a different time to other providers viz. BT.
> > ISTR that BT send the CLI before the first ring whereas VM send it after
> > the first ring.
>
> BT are actually the odd ones out. Their system allows for services to be
> delivered without the phone ringing, such as the SMS service.
>
> The after first ring standard is what the Americans did. BT does a line
> reversal, before the first ring, to silently signal an incoming call,
> and, if I remember correctly, the phone does a, brief, partial loop on
> the line, to indicate it wants the caller ID, and also to "wet" the line.

I would guess VM (or rather their constituent cable companies) bought in
American cable TV kit, so they got American telephone switching hardware
too. I wouldn't be surprised if that's where the difference originally
arose. It is also possible those cablecos' CLI predated BT's implementation.

I suppose it must now be a setting on their router, as that's what's
now generating the CLI. I'm surprised they gone with the BT standard here.
Presumably the router vendor needed to implement explicit support for it.

Theo

On Thu 11/05/2023 12:34, Theo wrote:
> David Woolley <david@ex.djwhome.demon.invalid> wrote:
>> On 10/05/2023 12:04, Woody wrote:
>>> IMSMC VM send the CLI at a different time to other providers viz. BT.
>>> ISTR that BT send the CLI before the first ring whereas VM send it after
>>> the first ring.
>>
>> BT are actually the odd ones out. Their system allows for services to be
>> delivered without the phone ringing, such as the SMS service.
>>
>> The after first ring standard is what the Americans did. BT does a line
>> reversal, before the first ring, to silently signal an incoming call,
>> and, if I remember correctly, the phone does a, brief, partial loop on
>> the line, to indicate it wants the caller ID, and also to "wet" the line.
>
> I would guess VM (or rather their constituent cable companies) bought in
> American cable TV kit, so they got American telephone switching hardware
> too. I wouldn't be surprised if that's where the difference originally
> arose. It is also possible those cablecos' CLI predated BT's implementation.
>
> I suppose it must now be a setting on their router, as that's what's
> now generating the CLI. I'm surprised they gone with the BT standard here.
> Presumably the router vendor needed to implement explicit support for it.
>

When we maintained it the VM switches in this area (ex Bell Cablemedia
and Yorkshire Cable) were all Nokia as far as I remember.