AudioCodes Mediant 4000 SBC User Manual page 440

Parameter
Play RBT To Transferee
sbc-play-rbt-to-xferee
[IpProfile_SBCPlayRBTToTr
ansferee]
User's Manual
call identifiers of the leg.

[1] Handle Locally = The SIP entity does not support INVITE
messages containing Replaces headers. The device terminates the
received INVITE containing the Replaces header and establishes a
new call between the SIP entity and the new call party. It then
disconnects the call with the initial call party, by sending it a SIP
BYE request.

[2] Keep as is = The SIP entity supports INVITE messages
containing Replaces headers. The device forwards the Replaces
header as is in incoming REFER and outgoing INVITE messages
from/to the SIP entity (i.e., Replaces header's value is unchanged).
For example, assume that the device establishes a call between A and
B. If B initiates a call transfer to C, the device receives an INVITE with
the Replaces header from C. If A supports the Replaces header, the
device simply forwards the INVITE as is to A; a new call is established
between A and C and the call between A and B is disconnected.
However, if A does not support the Replaces header, the device uses
this feature to terminate the INVITE with Replaces header and handles
the transfer for A. The device does this by connecting A to C, and
disconnecting the call between A and B, by sending a SIP BYE
request to B. Note that if media transcoding is required, the device
sends an INVITE to C on behalf of A with a new SDP offer.
Enables the device to play a ringback tone to the transferred party
(transferee) during a blind call transfer, for the SIP entity associated
with the IP Profile (which does not support such a tone generation
during call transfer). The ringback tone indicates to the transferee of
the ringing of the transfer target (to where the transferee is being
transferred).

[0] No (Default)

[1] Yes
Typically, the transferee hears a ringback tone only if the transfer
target sends it early media. However, if the transferee is put on-hold
before being transferred, no ringback tone is heard.
When this feature is enabled, the device generates a ringback tone to
the transferee during call transfer in the following scenarios:

Transfer target sends a SIP 180 (Ringing) to the device.

For non-blind transfer, if the call is transferred while the transfer
target is ringing and no early media occurs.

The 'Remote Early Media RTP Behavior parameter is set to
Delayed (used in the Skype for Business environment), and
transfer target sends a 183 Session Progress with SDP offer. If
early media from the transfer target has already been detected, the
transferee receives RTP stream from the transfer target. If it has
not been detected, the device generates a ringback tone to the
transferee and stops the tone generation once RTP has been
detected from the transfer target.
For any of these scenarios, if the transferee is put on-hold by the
transferor, the device retrieves the transferee from hold, sends a re-
INVITE if necessary, and then plays the ringback tone.
Note: For the device to play the ringback tone, it must be loaded with
a Prerecorded Tones (PRT) file. For more information, see
Prerecorded Tones File on page 632.
440
Mediant 4000 SBC
Description
Document #: LTRT-40203