SIP phone: Forward unattended call

The Event Type 33 - Private Ringing Outgoing can be used to forward unattended SIP calls. In order to work, it requires that the SIP device returns the SIP status "180 Ringing" when the phones starts to ring, and "200 OK" when connecting.

The forwarding function has been verified with:

• IP Dect System 6000
• X-Lite
• Grandstream GXP2000
• Cisco CM6 with Cisco IP Phone 7960
• Alcatel OmniPCX (OXO) via SIP trunking

Configuration example

Event programming for SIP phone forwarding

• The SIP phone is 9555, the SIP Registrar node is node number 73.
• When an intercom station calls 9555, the phone will start to ring, the ringing time is controlled by the "Private Ringing Time" timer (30 sec default). If not answered, the call will time out, and the event 33 is triggered. This event sets up a new call to directory number 9547 (which can be an intercom or another SIP phone).
  
• $C is needed to "speed up" the disconnection, so that the $DD command is not lost during the disconnection tone

In AlphaPro, go to Exchange and System -> Events, press Insert and create the following events:

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Event 1 - Transfer to local dirno 9547, if call not answered.

Event Owner:	Stations w/ UDP, Id: 8
Event type:	33 - Private Ringing Outgoing
Subevent:	0
When change to:	OFF
When related to:	Directory Number, Node: 73, Id: 9555
Action:	$C L%1.dir
	$DD L%1.dir L9547

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Note that the initiator of the call (A-subscriber) must be an intercom station, not a SIP phone. The call forwarding will not work if the A-subscriber is a SIP phone.

The event type 33 require AMC 10.30 or later.