Managing Extensions 59Some countries reserve numbers beginning with 11 for numbers ofnational importance. To accommodate this requirement, you can beginthe telephone extension range at 120.Changing ExtensionLength and RangesYou can view and change extension settings, such as extension lengthand extension ranges.If you are changing from a 3-digit to a 4-digit plan, import the 4-digit dialplan configuration file before you configure or autodiscover any devices.To view and change extension settings:1 On the Operations tab, click Settings. The Settings dialog box appears.2 Make the desired changes to the extension settings. Table 10 describeseach field.3 Click OK to enable your changes and exit the dialog box.Start ExternalDiscovery AtThe extension to use when autodiscovering external devices.The system assigns extensions starting with this number andincrementing upward as they are discovered. If the highestextension is reached, the system starts looking from thebeginning of the external range and selects the first unused one.Typically, systems do not use all of the available externalextensions from 600–799 in a 3-digit dial plan or from6000–7999 in a 4-digit dial plan.Default:■ 4-digit dial plan: 7250■ 3-digit dial plan: 750External KeysetPrefixIn Keyset mode, when a button on an NBX Business Telephonedirectly accesses an outside line, the NBX system must checkClass of Service. The system prepends the External Keyset Prefixvalue (typically 8, 9, or 0) when it makes a call in Keyset mode.Note 1: The NBX V3000 and the Superstack 3 NBX V5000 are shipped with afactory default 4-digit dial plan. If you import any 3-digit plan, you must manuallyspecify any 3-digit extension ranges that are not set by the imported plan. You mustalso manually change any device extensions so that they fall within the appropriaterange.Note 2: The NBX 100 is shipped with a factory default 3-digit dial plan. If you importany 4-digit plan, you must manually specify any 4-digit extension ranges that are notset by the imported plan. You must also manually change any device extensions sothat they fall within the appropriate range.Table 10 Dial Plan Extension Settings (continued)Field Purpose (See Notes 1 – 3)
