AASTRA 4225 for MX-ONE Telephony Switch - Manual (Page 15)

15 Dialog 4223 Professional/Dialog 4225 Vision
Description
Ring signals
Three different ring signals inform you about the type of the incoming
call. The signals shown in this section are the most used signals
worldwide. Many markets use signals that are adapted for the local
standards. If you get a signal that is not described or you cannot
identify, ask your system administrator.
Internal ring signal
External ring signal
Recall signal
(Callback reminder)