Consultation / Alternate; Call Transfer - AudioCodes Mediant 1000 User Manual

The hold and retrieve functionalities are implemented by REINVITE 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 gateway to enter Hold state and to play held tone
(configured in the gateway) to the PBX/PSTN. If the string 'a=sendonly' is received in
the SDP message, the gateway 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 gateway forwards the MOH to the held party.
Receiving Hold / Retrieve
When an active call receives Re-INVITE message with either the IP address 0.0.0.0 or
the 'inactive' string in SDP, the gateway stops sending RTP and plays a local Held
Tone.
When an active call receives Re-INVITE message with 'sendonly' string in SDP, the
gateway stops sending RTP and listens to the remote party. In this mode, it is
expected that on-hold music (or any other hold tone) is to be played (over IP) by the
remote party.

7.14.2 Consultation / Alternate

The consultation feature is relevant only for the holding party (applicable only to the
FXS module).
After holding a call (by pressing hook-flash), the holding party hears a dial tone and
can now initiate a new call, which is called a consultation call.
While hearing a dial tone, or when dialing to the new destination (before dialing is
complete), the user can retrieve the held call by pressing hook-flash.
The held call can't be retrieved while Ringback tone is heard.
After the consultation call is connected, the user can switch between the held and
active call by pressing hook-flash.

7.14.3 Call Transfer

There are two types of call transfers:
Consultation Transfer (REFER and REPLACES):
The common way to perform a consultation transfer is as follows:
In the transfer scenario there are three parties: Party A = transferring, Party B =
transferred, Party C = transferred to.
•
A Calls B.
•
B answers.
•
A presses the hook-flash and puts B on-hold (party B hears a hold tone).
•
A dials C.
•
After A completes dialing C, A can perform the transfer by on-hooking the A
phone.
•
After the transfer is complete, B and C parties are engaged in a call.
SIP User's Manual 416
Mediant 1000
Document #: LTRT-83302