User's Manual 578 Document #: LTRT-27055
Mediant 1000B Gateway & E-SBC
27.5.3 Blind Call Transfer
Blind call transfer is done (using SIP REFER messages) after a call is established between
call parties A and B, and party A decides to immediately transfer the call to C without first
speaking to C. The result of the transfer is a call between B and C (similar to consultation
transfer, but skipping the consultation stage).
You can also use the ManipulateIP2PSTNReferTo parameter to manipulate the destination
number according to the number received in the SIP Refer-To header. This is applicable to
all types of blind transfers to the PSTN (e.g., TBCT, ECT, RLT, QSIG, FXO, and CAS).
During blind transfer, the device initiates a new call to the PSTN and the destination
number of this call can be manipulated if the parameter is enabled. The following is an
example of such a blind transfer:
1. IP phone "A" calls PSTN phone "B", and the call is established.
2. "A" performs a blind transfer to PSTN phone "C". It does this as follows:
a. "A" sends a SIP REFER message (with the phone number of "C" in the Refer-To
header) to the device.
b. The device sends a Q.931 Setup message to "C". This feature enables
manipulating the called party number in this outgoing Setup message.
The manipulation is done as follows:
1. If you configure a value for the xferPrefix parameter, the value (string) is added as a
prefix to the number in the Refer-To header.
2. This called party number is then manipulated using the Destination Phone Number
Manipulation for IP-to-Tel Calls table.
3. The source number of the transferred call is taken from the original call, according to
its initial direction:
• Tel-to-IP call: source number of the original call.
• IP-to-Tel call: destination number of the original call.
• If the UseReferredByForCallingNumber parameter is set to 1, the source number
is taken from the SIP Referred-By header if included in the received SIP REFER
message.
This source number can also be used as the value for the 'Source Prefix' field in the
Destination Phone Number Manipulation for IP-to-Tel Calls table. The local IP address
is used as the value for the 'Source IP Address' field.
Note: Manipulation using the ManipulateIP2PSTNReferTo parameter does not affect
IP-to-Trunk Group routing rules.
27.6 Call Forward
For digital interfaces: The device supports Call Deflection (ETS-300-207-1) for Euro ISDN
and QSIG (ETSI TS 102 393) for Network and User sides, which provides IP-ISDN
interworking of call forwarding (call diversion) when the device receives a SIP 302
response.
Call forward performed by the SIP side: Upon receipt of a Facility message with Call
Rerouting IE from the PSTN, the device initiates a SIP transfer process by sending a SIP
302 (including the Call Rerouting destination number) to the IP in response to the remote
SIP entity's INVITE message. The device then responds with a Disconnect message to the
PSTN side.
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