162 3Com VCX V7111 VoIP SIP Gateway User ManualWorking with Supplementary ServicesThe VCX V7111 SIP FXS and FXO gateways support the following supplementary services: Hold \ Retrieve; see Call Hold and Retrieve on page 162. Consultation \ Alternate; see Consultation / Alternate on page 162. Transfer (Refer + Replaces); see Call Transfer on page 163. Call Forward (3xx Redirect Responses); see Call Forward on page 163. Call Waiting (182 Queued Response); see Call Waiting on page 164. Message Waiting Indication (MWI); see Message Waiting Indication on page 164.To activate these supplementary services (Hold, Transfer, Forward, Waiting and MWI) on theVCX V7111 gateway, enable each service’s corresponding parameter either from the WebInterface or via the ini file. Note that all call participants must support the specific usedmethod.Call Hold and RetrieveInitiating Hold/Retrieve Active calls can be put on-hold by pressing the phone's hookflash button. 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. Call retrieve can be performed only by the holding party while the call is held and active. The holding party performs the retrieve by pressing the hookflash. After a successful retrieve, voice is connected again. Hold is performed by sending a REINVITE with the IP address 0.0.0.0 or “a=sendonly” inthe SDP according to the parameter ‘HoldFormat’.Receiving Hold \ Retrieve When an active call receives REINVITE message with either the IP address 0.0.0.0 orthe “inactive” string in SDP, the gateway stops sending RTP and plays a local Held Tone. When an active call receives REINVITE message with “sendonly” string in SDP, thegateway stops sending RTP and listens to the remote party. In this mode, it is expectedthat on-hold music (or any other hold tone) is to be played (over IP) by the remote party.Consultation / Alternate The consultation feature is relevant only for the holding party (applicable only to the VCXV7111/FXS gateway). After holding a call (by pressing hookflash), the holding party hears dial tone and cannow initiate a new call that is called a consultation call. While hearing dial tone, or when dialing to the new destination (before dialing iscomplete) the user can retrieve the held call by pressing hookflash. 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 activecall by pressing hookflash.
