The line settings shown in the system configuration will change according to the types of trunk cards installed in the control unit or added using external expansion modules.

Trunk Incoming Call Routing

Trunks are categorized as external or trunk. The trunk type affects how the system routes calls received on that trunk and the routing of calls to the trunk.

Line Groups

Each system trunk (or in some cases individual trunk channels) can be configured with an Incoming Group ID and an Outgoing Group ID. These group IDs are used as follows:

• Incoming Call Routes - For incoming calls on external trunks, the Incoming Group ID of the trunk is one of the factors used to match the call to one of the configured incoming call routes.

• Short Codes - For dialing which matches a short code set to a Dial feature, the short codes Line Group ID can indicate either an ARS form or to use a trunk from set to the same Outgoing Group ID. If the call is routed to an ARS form, the short codes in the ARS form will specify the trunks to use by matching Outgoing Group ID.

Removing Unused Trunks

In cases where a trunk card is installed but the trunk is not physically connected, it is important to ensure that the trunk is disabled in the configuration. This can be done on most trunks using by setting the line's Admin setting to Out of Service.

This is especially important with analog trunks. Failure to do this may cause the system to attempt to present outgoing calls to that trunk. Similarly, where the number of channels subscribed is less than those supportable by the trunk type, the unsubscribed channels should be disabled.

Clock Quality

Calls between systems using digital trunks (for example E1, E1R2, T1 PRI and BRI) require an common clock signal. The system will try to obtain this clock signal from a PSTN exchange through one of its digital trunks. This is done by setting the Clock Quality setting of that line to Network. If there are multiple trunks to public exchanges, another trunk can be set as Fallback should the primary clock signal fail. Other trunks should be set as Unsuitable.