ISDN PRI Prerequisites 227■ CSU — A CSU (Channel Service Unit) is required with each T1installation. You must have an external CSU when you use the3C10116C T1 Digital Line Card. 3C10116D includes an onboard CSU.Many CSUs support conversion of ESF (with B8ZS) services into D4(with AMI). In some locations it may be easier to order the T1 as ESFwith B8ZS and perform the conversion in the CSU. You must verifythat the external 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)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.
