Aastra Telecom SIP 57I - Manual (Page 445)

Advanced Operational Features
41-001160-00, Release 2.1, Rev 04 6-7
Configuring Advanced Operational Features
Advanced Operational Features SIP Message Sequence for Blind Transfer
The SIP message sequence for Blind Transfer avoids the transfer target having
two simultaneous calls. Prior to release 1.4, a CANCEL message was sent to the
transfer target (if it was in a ringing state) after sending a REFER to the transferee
to complete the transfer. In the 1.4 and later releases, the CANCEL is now sent
before the REFER message.
The following parameter allows the system administrator to force the phone to use
the Blind Transfer method available in software versions prior to 1.4:
sip cancel after blind transfer
This parameter is configurable via the configuration files only.
Configuring SIP Message Sequence for Blind Transfer
Configuration Files
For the specific parameter you can set in the configuration files for enabling/disabling the blind transfer
method, see Appendix A, the section,
“Blind Transfer Setting” on page A-172.