Ringer tones
Ringtones are not part of the PBX software. Only the ringtones available in the telephones are used.
Call type and number-dependent ringtones 
To telephones that support this, the PBX sends information on the call type in the alert info in SIP Invite. The ringtones available in the phone then can be assigned to the different call types using the alert info. This allows, for example, different call types such as internal, external, group and door calls to be distinguished by different ring tones.
In addition, the PBX also transmits the calling or called number depending on the call type. On telephones that can process the transmitted information (COMfortel D-series telephones, firmware version 2.6B or later), it is thus possible to distinguish not only the call types but also the calling and called numbers on the basis of the ringtones.
The following data is transmitted by the PBX in the alert info:
alert-internal-[calling user number] for internal calls
alert-group-[called group number] for internal group calls
alert-external-[called external number] for external calls
alert-door-[calling door number + door bell button] for door calls
Examples:
alert-internal-222 for internal calls from the user number 222
alert-group-123 for internal calls to the group number 123
alert-external-911977 for calls to the external telephone number 911977
alert-door-511 for calls from the door 51, door bell button 1
*You will find more information about the assignment of ringtones in the telephone in the instruction of the telephone.
*Important: The transmission of the calling and called numbers is only available with feature level 3 or higher. If you want to use this function, please contact your dealer or system partner.
*Further help under Feature level
*Note: Some telephones support an assignment of ringtones to the transferred phone number, independent of the alert info.
*For more information on this, please refer to the instructions for the telephone.
Configuration 
For telephones that support an assignment to ringtones based on the SIP alert info, switch on the SIP alert info.
Telephones > Assignment >
Set the ringing frequency for any existing analogue telephones.
User > Functional Overview > Global settings