[Freeswitch-users] Any Idea how to let the phone ring with a different ring tone

Hello, for emergency issues I would like to let a phone ring with a different ringer tone so that anybody can hear by the ringer tone that this call is an alarm call. I know that for this purpose an "Alert-Info" can be added to the SIP header. But how has this to be invoked in FS, especially when I want make a group call to a number of phones? Anybody has an idea how to solve this? Best regards Peter