AudioCodes Mediant 3000, User Manual

Page: 378 / 872

User's Manual 378 Document #: LTRT-89729
Mediant 3000
26.1 Call Hold and Retrieve
Call Hold and Retrieve:

The party that initiates the hold is called the holding party; the other party is called the
held party. The device can't initiate Call Hold, but it can respond to hold requests and
as such, it's a held party.

After a successful Hold, the holding party hears a dial tone (HELD_TONE defined in
the device's Call Progress Tones file).

After a successful retrieve, the voice is connected again.

The hold and retrieve functionalities are implemented by re-INVITE messages. The IP
address 0.0.0.0 as the connection IP address or the string ‘a=inactive’ in the received
re-INVITE SDP cause the device to enter Hold state and to play the held tone
(configured in the device) to the PBX/PSTN. If the string ‘a=sendonly’ is received in
the SDP message, the device stops sending RTP packets, but continues to listen to
the incoming RTP packets. Usually, the remote party plays, in this scenario, Music on
Hold (MOH) and the device forwards the MOH to the held party.
You can also configure the device to keep a call on-hold for a user-defined time after which
the call is disconnected, using the HeldTimeout parameter.
26.2 Call Transfer
This section describes the device's support for call transfer types.
26.2.1 Consultation Call Transfer
The device supports Consultation Call Transfer. 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 Explicit Call Transfer (ECT, according to ETS-300-367, 368, 369) supplementary
service is supported for 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.