[Asterisk-Users] Customized ring tones

[ht at phonitel.com]

Hello,
I have very few knowledge of this area. But mobile operator in belgium has
launched "Hello Tone". So if you call somebody on mobile network, you can
listen to U2 music, or Bethoven (chosen by callee) while the phone is ringing,
even if you call from different network operator.

Before I see this, I thought that phone ring tones are standards. As this can be
done, can it be implemented in Asterisk if interconnected through ISDN to a
carrier during incoming calls?