[Asterisk-Users] can't get caller id?

[Steve Underwood]

Steven Critchfield wrote:

> Callerid in the Us is signaled with FSK between the first and second
>
>ring. For more information, you will need to consult the source as it
>will be definitive.
>
>So far, I think it has been established that in the UK, the callerid is
>sent after a line reversal and before the first ring.
>
The UK uses a similar FSK message format to the US (not identical, but 
similar). However UK ringing doesn't have a huge silence period in it. 
Therefore, they send the caller ID before the first ring. Does anyone 
know why they use a reversal to indicate the CLI is coming? Most digital 
exchange lines are incapable of reversing the line, so it seems like 
this choice forces the use of a new line card for any sub. who joins the 
CLI service - weird! Various alternatives seem simpler.

In something like * it would not be necessary to look for the reversal. 
Conintuously running the FSK receiver isn't that big a compute load. It 
could be run continuously between calls, and pick up any FSK messages 
which arrive.

>I think it has also been established that some locations have callerid
>as either dtmf or mf. I don't usually pay attention to this as much
>because I can't help them.
>
DTMF is used in some places. Japan uses FSK, but a rather different 
message format. There isn't a whole lot of global standardisation in CLI!

Regards,
Steve