Reference13r2:PBX/Objects/Trunk Line

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The Trunk Line object is typically used to register gateways to external lines. Several registrations are accepted. Calls sent to the trunk object are sent to the registrations in a round-robin manor. If the call to a registration fails in a way that indicates a local problem the next registration is tried.

Some general diversions can be configured for incoming calls e.g. for calls to invalid numbers.

Trunk Object specific configuration

Destination (Name or Number) to which calls are forwarded, which dialed the same Trunk object. This is typically used if the number of the Trunk object (e.g. 0) shall be used as extension number of the switchboard for incoming calls. If the Internal checkmark is set, this is executed also if the trunk is called from within the PBX with a calling party number matching the number of the trunk object. This can happen if for example an escape is configured for the node of the trunk object matching the number of the trunk object.
Destination (Name or Number) to which calls are forwarded, which dialed an incomplete number. If the incoming call is enblock this can be determined immediately. For overlap receiving calls a timeout of 4s is used. Sometimes it is desired that calls without extension number are sent to the switchboard. In this case the number of the switchboard should be configured here.
Destination (Name or Number) to which calls are forwarded, which dialed an invalid number. Typically the number of the switchboard is configured here so that incoming calls with an invalid extension are not lost. This is executed also for calls rejected because of the 'Reject ext. Calls' property at a called object.
Destination (Name or Number) to which calls are forwarded, which dialed a busy number. If a CFB is configured at a called user this takes precedence. A CFB at at the called user to a number - turns this off for this user.
Calls which are rejected by the user (busy after alert), can be redirected to a configurable destination.
No Answer
Destination (Name or Number) to which calls are forwarded, which dialed a destination which exists, but does not answer. The timeout value is configured in the Response Timeout field (on PBX/General or at the User object) which is used for CFNR as well. (There is no field Timeout configurable for this anymore) If a CFNR is configured at a called user this takes precedence. A CFNR at the called user to a number - turns this off for this user.
Reroute supported
This check box turn on rerouting of incoming calls which are diverted to the same Trunk object. Normally an incoming call which is diverted to the same Trunk object is sent out on the Trunk as normal outgoing call. If this option is checked a reroute request is sent out instead. If the call is received from an ISDN interface this is mapped to partial rerouting. By doing this no channel is used on the ISDN interface for such a call (instead of 2) and the original calling party number is sent to the final destination by the ISDN network. Rerouting is supported only for CFU and CFB, not for CFNR.
If your Provider does not support (partial) rerouting and you nevertheless configure Reroute supported, the call forward will fail with a cause code Recovery on timer expiry.
Set Calling=Diverting No
Concerns calls that arrive on the PBX via the Trunk Line PBX object and are then forwarded by CFU, CFB or CFNR again to the Trunk Line object. For example: Subscriber A calls subscriber B. Subscriber B forwards the call from subscriber A to subscriber C.
The CGPN (Calling Party Number) remains unchanged for a call diversion. Merely the DGPN (Diverting Party Number) is also sent as information, so that both call numbers are visible at the diversion destination (subscriber C). For an external call diversion to the PSTN, it may not be permitted to use an external CGPN (subscriber A), however. Therefore, the CGPN must be replaced by an associated call number, in this case the DGPN (subscriber B). If this check box is not enabled, the local telephone office, in such as case, will automatically replace the CGPN through "screening".
If you enable this check box, the diversion call is signalled as a normal outgoing call. The CGPN is then a number that belongs to the connection (subscriber B).
Set Diverting=Calling No
For calls from the PBX to the trunk, the calling party number (CGPN) is set as diverting number (DGPN) (a.k.a. leg2 info) if there is none yet in the call. If set, the party the call needs to be billed to is always included in the DGPN thus
Discard received diverting No
If set, received diverting info within calls from the trunk are discarded
Outgoing Calls restricted
If this checkmark is set all calls sent out on the Trunk object are sent with CLIR (Calling Line Identification Restricted).
Automatic Hangup
If this checkmark is set calls, which were already connected and then disconnected by remote party, are automatically released (hung up) two seconds after the disconnect, even if in-band info was indicated with the disconnect. This is useful when providers indicate but do not provide in-band info, or in general, because most providers only provide a busy tone in this situation and no announcement, so 2s are more then enough.
Outgoing Calls CGPN
If a number is configured here all calls sent out to the Trunk object are sent with this number as Calling extension. For example the number of the switchboard can be configured here so that callbacks are not sent to the original caller but to the switchboard.
Set incoming call UUI
If configured, this is set to each call coming in thru this gateway object as User User Information (UUI). The UUI can be used to set the identity header on a SIP call, when sending the call on a SIP interface in the gateway.
Set outgoing call UUI
If configured, this is set to each call going out thru this gateway object as User User Information (UUI).
Outgoing No Name
If this checkmark is set no calling name nor calling name display information is sent with outgoing calls
No Presence/Dialog Subscribe
If checked, no presence or dialog subscriptions are forward out through this Trunk line object.
Fake Connect on inc. Call
If this checkmark is set an incoming call is connected (send out a fake connect message) as soon as inband info is available from the destination of the call even if the destination did not connect the call already. This is especially useful for call forward out to a public network, so that the caller can hear the real inband info from the public network. Also timeouts can be avoided in such a case for the incoming call if the call is forwarded to a destination with slow alert or connect (e.g. GSM). Since v10 if there is no in-band info, now an alert is sent on this call in this case.
The filter configured here restricts the numbers which may be called by through this object. "Called by" means restriction to incoming calls only.
Name as Number
This option allows to send a Name of a PBX object as calling number for outgoing calls. The source name of the call is compared to the first field. If the name starts with the configured string, any digit in the remaining name is sent as calling line id. The second field may contain a number which is added as prefix to the calling line id. For incoming calls the called number is matched to the second field and in case of a match a name is called composed of the first field and any additional dialed digits. This way the same number can be used to call an endpoint as is displayed as calling line id.
If the configured name starts with '?' for a match the "External" field configured at a user is used.
This works only for users replicated to this PBX.


The device configuration is used as always to allow the registrations of devices. In case of a trunk object this is typically a gateway or SBC.

The name of the device serves one special purpose, if the name starts with '#'. In this case, if a call is sent out to the trunk and the calling party number of this calls matches the digits following the '#', not just the next gateway is used, but instead the registration with the matching name is used. Incoming calls on such a registration are sent to the number following the '#'. This way multiple registrations to SIP providers can be mapped to internal numbers for incoming and outgoing calls.

Multiple Gateway Registrations

If multiple Gateways are registered to a Trunk Line object, Gateways registered to the same devices Hardware Id are used in round-robin. If the Gateways register to different devices Hardware Id, they are used in the sequence of the configured devices Hardware Ids.

Call Diversions

If configured a CFU is executed, so calls to the Trunk object are diverted.
A CFB is executed if a call is rejected with User Busy by remote destination
A CFNR is executed if a call is rejected because of a local problem (no channel, no gateway registered, ...)

Group Indications

The trunk object generates group indications for incoming and outgoing calls including a park position (a number from 0 to n), which is sort of a virtual channel number. Together with Park function keys on the phone this can be used to simulate an oldstyle key system, so that each phone can have Line keys (the Park function key) for each available line (the position). With these Line keys a line can be aquired, monitored, a call can be parked on the line and picked up from the line.