Change Ring Tone for Transferred Calls

We use SIP protocol on our Asterisk system. I have need to audibly distinguish between transferred calls and inbound calls. How can I achieve this?

I do not see any follow-on to this post. This is a serious issue for me as well because I need to have incoming calls available to all users. Once the call is answered and then transferred, the users cannot distinguish between an original incoming call and the transferred call. There must be some simple way to assign a new ring tone to the call after the original incoming call has been answered.

Run all transfers through a macro that sets ALERT_INFO to a different setting (ringtone)?

Thanks, Malcolm, I will get the programmers to look at that.