User`s manual

SIP User's Manual 8. Telephony Capabilities
Version 5.0 207 October 2006
8 Telephony Capabilities
8.1 Working with Supplementary Services
The gateway gateway supports the following supplementary services:
 Call Hold / Retrieve (refer to Section 8.1.1 on page 207)
 Call Transfer (refer to Section 8.1.2 on page 207)
 Call Forward (doesn't initiate call forward, only responds to call forward request)
 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.
Note: 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.
8.1.1 Call Hold and Retrieve Features
 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.
 After a successful hold, the held party should hear HELD_TONE, defined in the
gateway's Call Progress Tones file.
 Retrieve can be performed only by the holding party while the call is held and active.
 After a successful retrieve the voice should be connected again.
 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.
8.1.2 Call Transfer
There are two types of call transfers:
 Consultation Transfer
 Blind Transfer
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 hookflash and puts B on-hold (party B hears a hold tone).
 A dials C.