3Com VCX V7122, User Manual, Page: 247 / 488

V7122 Gateway User Guide
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C
HAPTER
8: T
ELEPHONY
C
APABILITIES
Working with Supplementary Services
The gateway supports the following supplementary services:
ƒ Call Hold / Retrieve (see Call Hold and Retrieve Features )
ƒ Call Transfer ( Call Transfer )
ƒ Call Forward (doesn't initiate call forward, only responds to call forward request)
ƒ Call Waiting
The gateway SIP users are only required to enable the Hold and Transfer features. The call
forward (supporting 30x redirecting responses) and call waiting (receive of 182 response)
features are enabled by default. Note that all call participants must support the specific used
method.
When working with application servers (such as BroadSoft’s BroadWorks) in
client server mode (the application server controls all supplementary services and
keypad features by itself), the gateway’s supplementary services must be
disabled.
Call Hold and Retrieve Features
ƒ The party that initiates the hold is called the holding party, the other party is called the
held party. The gateway can't initiate the hold, but it can respond to hold request, and as
such it is a held party.
ƒ After a successful hold, the held party should hear HELD_TONE, defined in the
gateway's Call Progress Tones file.
ƒ Retrieve can be performed only by the holding party while the call is held and active.
ƒ After a successful retrieve the voice should be connected again.
ƒ
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
REINVITE 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=recvonly’ 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.