| UNIT 4: PROGRAMMING - LESSON 3: SYSTEM PROGRAMMING BY PC System Menu (continued...) External Call Block The External Call Block Menu is used to determine which Trunk Groups can be used to make outgoing calls on a COS basis. A unique setting is available for each time mode (day/lunch/break/night). To prevent a COS from making outgoing calls on a particular Trunk Group, you simply select the appropriate cell (which turns blue to indicate that calls are blocked) and click apply. One thing to keep in mind when using the External Call Block feature is that it will prohibit all access to the lines within the blocked Trunk Group. This means it will prevent any outgoing calls including those set as Emergency Dial Numbers from being made. For this reason it is recommended that when attempting to prevent all outgoing calls from a particular extension, that the Toll Restriction feature be used instead. When an extension is toll restricted, it can still make calls to the Emergency Dial Numbers. In the example below: COS 1 and 4 can make calls on all lines. COS 2 can make calls on Trunk Group 1 lines only. COS 3 can make calls on Trunk Group 2 lines only. Internal Call Block Internal Call Block determines the restrictions placed on making and receiving intercom calls. Extensions, Incoming Call Distribution groups, and doorphones can be programmed to not receive intercom calls from those belonging to a certain COS. To prevent a COS from receiving calls from a particular COS you simply select the appropriate cell (which turns blue to indicate calls are blocked) and click apply. In the example below: COS 1 can make calls to all extensions. COS 2 can make calls to COS 1 only. (COS 2 cannot make calls to COS 2.) COS 3 can make calls to COS 3 only.