Setting CID names for known numbers, how to do it?

Hi!

I want to add a method that adds a CID name to numbers I know. Since all 
calls are coming in over ISDN I do not have names. I just have the CID 
number.
I guess I could do it in "from-pstn-custom". But how to start? Or is 
"ext-did-custom" the better place?
I additionally want to use a different ringtone for external calls. I 
can set it with "SetVar(ALERT_INFO=http://asterisk/ringtones/ring.wav)" 
I'm just not so sure where to add this.
Can somebody help me?

Thx!

Michael


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