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VoIP Subscriber Gateways
Figure below shows an algorithm of 'Unattended calltransfer' service operation.
Fig. 7 - 'Unattended calltransfer' service operation algorithm
'Local Calltransfer'
service allows to transfer the call within the gateway without external REFER
message sending in case when Subscriber C is local TAU subscriber and call was made directly, without
proxy server. If subscriber C is an external subscriber or local one that has been dialed using proxy
server,
'Local Calltransfer'
service performs as
'Attended Calltransfer'
, i.e. call transfer is carried out by
sending the REFER message to subscriber B.
4.2
Call Waiting
This service allows informing 'busy' users about new incoming calls with a special signal.
Upon receiving this notification, a user can answer or reject a waiting call.