140 CHAPTER 7: E1 ISDN PRI D IGITAL LINE CARDAdding an E1Digital Line CardThe following sections tell you how to add an E1 Digital Line Card to anNBX system:■ Preparing the NBX System for E1 Cards■ Ordering DID, CLIP, and MSN Services for E1■ Inserting the E1 Digital Line CardPreparing the NBXSystem for E1 CardsBefore you insert the E1 Digital Line Card into the chassis, order an E1line, with the specifications you want, from your telephone carrier, andhave them install the line.Ordering DID, CLIP,and MSN Servicesfor E1When you order E1 with DID, CLIP, or MSN services, the local telephonecarrier assigns a block of telephone numbers to you. Usually, you canrequest a specific range of numbers, but sometimes the carrier assignsnumbers other than the ones you request.You may be able to request that the local telephone carrier pass you aspecific number of digits for each incoming telephone call. Sometimesthe carrier does not offer any choice. In either situation, you need toknow how many digits the carrier passes.Example: Carriers commonly pass either the last three digits or last fourdigits of the number for each incoming call. Sometimes the last digits ofthe telephone numbers the carrier assigns to you do not match thetelephone extension numbers you want to use for internal calls. You cancreate entries in your Dial Plan configuration file to translate the incomingnumbers into the corresponding extension numbers.Example: You want to use internal extensions from 4000 through 4999,but the local telephone carrier assigns you numbers from 617-555-3500through 617-555-4499. You can create translator entries in the Dial Planconfiguration file to translate an incoming digit sequence such as 3795into extension number 4295, and a sequence such as 4213 into 4713.The configuration would require several translator entries to handlesubsets of the total range. A unique set of entries would handle incomingdigit sequences from 3500 through 3599, from 3600 through 3699, andeach of the other sequences in which the first two digits were unique inthe range from 37XX through 44XX.
