Interworking Keypad DTMFs for SIP-to-ISDN Calls

The device can interwork DTMF tones received from the IP to the PSTN, using the ISDN Keypad Facility information element (IE) in Q.931 INFORMATION messages.

If the device receives from the IP side an INVITE message whose called party number (To header) contains the asterisk (*) or pound (#) character, or a SIP NOTIFY or SIP INFO message that contains these characters (e.g., 123#456), the device sends the character and the digits positioned to its right, as Keypad IE in the INFORMATION message. The device sends only the digits positioned before the character to the PSTN (in SETUP message) as the called party number. For example, if the device receives the below INVITE, it sends "123" to the PSTN as the called party number and #456 as Keypad IE in the INFORMATION message:

INVITE sip:%7B54443994-BDFF-413C-AE4F-D039B0FFB134%7D@192.168.100.214:5064;transport=tcp;rinstance=9f25c4452eff4acb SIP/2.0
To: sip:123#456@192.168.100.214;user=phone;x-type=unknown;x-plan=unknown;x-pres=allowed

The destination number can be manipulated when this feature is enabled. Note that if manipulation before routing is required, the * and # characters should not be used, as the device will handle them according to the above keypad protocol. For example, a manipulation rule should not be configured to add #456 to the destination number. If manipulation after routing is required, the destination number to be manipulated will not include the keypad part. For example, if you configure a manipulation rule to add the suffix 888 and the received INVITE contains the number 123#456, only 123 is manipulated and the number dialed toward the PSTN is 123888; #456 is sent as keypad.

To enable this feature, use the ISDNKeypadMode parameter.