AudioCodes Mediant 500L - 27 Configuring Supplementary Services; Call Hold and Retrieve

Version 7.2 569 Mediant 500L Gateway & E-SBC
User's Manual 27. Configuring Supplementary Services
27 Configuring Supplementary Services
This section describes SIP supplementary services that can enhance your telephone
service.
Note:
• All call participants must support the specific supplementary service that is used.
• When working with certain application servers (such as BroadSoft’s BroadWorks)
in client server mode (the application server controls all supplementary services
and keypad features by itself), the device's supplementary services must be
disabled.
27.1 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.

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.