ISDN PRI Prerequisites 187■ CSU — An external CSU (Channel Service Unit) is required with eachT1 installation. Many CSUs support conversion of ESF (with B8ZS)services into D4 (with AMI). In some locations it may be easier to orderthe T1 as ESF with B8ZS and perform the conversion in the CSU. Youmust verify that the CSU supports this conversion.ISDN PRIPrerequisitesBefore you install and configure ISDN PRI services on T1 circuits, gatherthe following information and have it available at the time of installation:■ All telephone numbers to be activated■ PRI circuit ID■ Carrier’s testing department name and telephone numbers■ Carrier’s circuit provisioning department names and numbers■ Carrier’s account representative account information■ Requested smart jack be installed in customer’s suite (not at theminimum point of entry)CSU Required Each PRI installation requires an external Channel Service Unit (CSU).ISDN PRIRecommendationsFor ISDN PRI services, 3Com recommends the settings discussed in thefollowing sections.■ Framing Type — The recommended (also the default) configurationis Extended Super Frame (ESF).The multi-frame formats F4, F12 (D4 or SF), and F72 are alsosupported.■ Zero Code Suppression — The recommended (also the default)configuration is B8ZS.AMI is also supported, but 3Com does not recommend this choice.■ DID Applications — For DID or DNIS, 3Com recommends that youorder telephone numbers that easily fit in the NBX system numberingplan. If possible, use 3 or 4 digit DID/DNIS codes, which allow forsimple dial plan implementation.
