Page History

...

In the external_replaces extension, you will have access to the following channel variables:

• SIPTRANSFER: Set This variable is set to "yes" to indicate upon entering the external_replaces extension, and indicates that a SIP transfer is happening. This is only useful if, for whatever reason, you are using the the external_replaces extension for additional purposes than a SIP remote attended transfer.
• SIPREFERRINGCONTEXT: This is the dialplan context in which the external_replaces extension was found. This may be useful if your external_replaces extension calls into subroutines or jumps to other contexts.
• SIPREFERTOHDR: This is the SIP URI in the Refer-To header in the REFER request sent by the transferring party.

...