[asterisk-users] SIP call, updated with CID as it becomes available

[Gordon Henderson]

On Wed, 11 Jun 2008, Steve Totaro wrote:

> On Wed, Jun 11, 2008 at 10:57 AM, Gordon Henderson
> <gordon+asterisk at drogon.net> wrote:
>> On Wed, 11 Jun 2008, Steve Totaro wrote:
>>
>>> "That brings up a question though, on a regular landline with caller ID
>>> the phone rings right away, it just doesn't display caller ID info
>>> until a couple of rings.  Why not have that option in Asterisk?"
>>
>> Intersting idea... However, I live in a country where on a regular
>> landline with caller ID, the caller ID is displayed before the phone
>> rings, so make sure it's an option and not hard-wired...
>>
>> Gordon
>>
>
> Gordon,
>
> Yes, an option.
>
> So in your country, the caller hears ringing for a few seconds before
> the destination phone rings since caller ID is sent via analog
> signaling?

Sometimes they get a brief ring, although a lot of the time it's possible 
to pickup the call without the caller hearing any ring at all. (or you 
hearing any ring if your phone displays the number before it rings and you 
pick it up quick enough).

Asterisk can Answer() it more or less as soon as it sees the line reversal 
and has seen the CID sent (< 1 second). Sooner with ignorecid set.

The CID is sent as a burst of 1200 baud FSK tones AIUI, but I'd have to 
look that up to be sure...

BT's SIN 242 - Page 8 has the details - looks like the whole thing from 
line reversal through signaling, V.23 data should be under 1 second, but 
it can be up to 3 seconds - the data part says "<= 2.5 secs, typically 
500ms". BT typically sends nothing (witheld), a 10 or 11 digit number, or 
INTERNATIONAL....

Gordon