On Wed, 16 May 2001, Jonathan Peterson wrote:
> At 21:08 15/05/01 +0100, you wrote:
>
> >They already offer it.
> >You can bar up to ten numbers (IIRC). I don't know how it deals
> >with withheld numbers. Never checked.
>
> I'm sure I remember reading somewhere that you always send your CID when
> you make a phone call. If you choose to withhold the ID, it still gets
> sent, it just gets sent with a 'do not disclose' flag set, which all (BT
> approved) phones and services (like 1471) must honour. Therefore it should
> be easy for BT themselves to offer something that can bar CID witheld
> calls.
>
> But this might be wrong, or might just be how the US system works or
> something.
umm maybe in the US ..
In the UK the CLDN (calling line dialled number) is stripped at the
terminating exchange and replaced with a 'reason for abscence of dialled
number' code ('O' for unavailable, 'P' for withheld .. theres logic in
there somewhere ;)
if it really did send it on it would just be too easy to make a box to
display numbers whether they were withheld or not. Obviously the telcos
still have access to the routing information internally, for call tracing
and such, but its not passed on to the customer.
I do keep intending to do something cute with my ISDN adapter and log the
stuff coming out of the D channel and see whats in there ... but time has
prevented it etc.
--
Robin Szemeti
Redpoint Consulting Limited
Real Solutions For A Virtual World
