Version 6.2 435 February 2011
SIP User's Manual 8. IP Telephony Capabilities
The SIP call flow diagram below illustrates the Collecting Digits Mode.
Figure 8-22: Call Flow for Collecting Digits Mode
8.3.5.2.2.3 FXO Supplementary Services
The FXO supplementary services include the following:
Hold / Transfer toward the Tel side: The ini file parameter LineTransferMode must
be set to 0 (default). If the FXO receives a hook-flash from the IP side (using out-of-
band or RFC 2833), the device sends the hook-flash to the Tel side by performing one
of the following:
• Performing a hook flash (i.e., on-hook and off-hook)
• Sending a hook-flash code (defined by the ini file parameter HookFlashCode)
The PBX may generate a dial tone that is sent to the IP, and the IP side may dial digits
of a new destination.
Blind Transfer to the Tel side: A blind transfer is one in which the transferring phone
connects the caller to a destination line before ringback begins. The ini file parameter
LineTransferMode must be set to 1.
The blind transfer call process is as follows:
• FXO receives a REFER request from the IP side
• FXO sends a hook-flash to the PBX, dials the digits (that are received in the
Refer-To header), and then drops the line (on-hook). Note that the time between
flash to dial is according to the WaitForDialTime parameter.
• PBX performs the transfer internally
Hold / Transfer toward the IP side: The FXO device doesn't initiate hold / transfer as
a response to input from the Tel side. If the FXO receives a REFER request (with or
without replaces), it generates a new INVITE according to the Refer-To header.
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