Call Transfer - AudioCodes Mediant 1000 User Manual

18.5.2.4 Call Transfer

The device supports the following call transfer types:

Consultation Transfer (see 'Consultation Call Transfer' on page 296)

Blind Transfer (see 'Blind Call Transfer' on page 297)
Notes:
18.5.2.4.1 Consultation Call Transfer
The device supports Consultation Call Transfer (using the SIP REFER message and
Replaces header). The common method to perform a consultation transfer is described in
the following example, which assumes three call parties:

Party A = transferring

Party B = transferred

Party C = transferred to
1. A Calls B.
2. B answers.
3. A presses the hook-flash button and places B on-hold (party B hears a hold tone).
4. A dials C.
5. After A completes dialing C, A can perform the transfer by on-hooking the A phone.
6. After the transfer is complete, B and C parties are engaged in a call.
The transfer can be initiated at any of the following stages of the call between A and
C:
•
Just after completing dialing C phone number - transfer from setup.
•
While hearing Ringback – transfer from alert.
•
While speaking to C - transfer from active.
The device also supports attended (consultation) call transfer for BRI phones (user side)
connected to the device and using the Euro ISDN protocol. BRI call transfer is according to
ETSI TS 183 036, Section G.2 (Explicit Communication Transfer – ECT). Call transfer is
enabled using the EnableTransfer and EnableHoldtoISDN parameters.
The Explicit Call Transfer (ECT, according to ETS-300-367, 368, 369) supplementary
service is supported for BRI and PRI trunks. This service provides the served user who has
two calls to ask the network to connect these two calls together and release its connection
to both parties. The two calls can be incoming or outgoing calls. This service is similar to
NI2 Two B-Channel Transfer (TBCT) Supplementary Service. The main difference is that in
ECT one of the calls must be in HELD state. The ECT standard defines two methods -
Implicit and Explicit. In implicit method, the two calls must be on the same trunk. BRI uses
the implicit mechanism, and PRI the explicit mechanism.
SIP User's Manual
•
Call transfer is initiated by sending REFER with REPLACES.
•
The device can receive and act upon receiving REFER with or without
REPLACES.
•
The device can receive and act upon receiving INVITE with REPLACES,
in which case the old call is replaced by the new one.
•
The INVITE with REPLACES can be used to implement Directed Call
Pickup.
296
Mediant 600 & Mediant 1000
Document #: LTRT-83310