exten => 200,1,NoOp()
same => n,Answer()
same => n,SIPAddHeader("Alert-Info: <ringding>")
same => n,Queue(sales-queue)
I dial 200, I hear my ringding ringtone, which is not the default ringtone for my phones, on each of my called phones. It works for both permanent Queue members (defined statically in queues.conf, e.g. SIP/101), as well as login/logout members who've logged themselves in via the Queues app on the phone.