The ADTRAN T1 ESF CSU is a full-featured T1 Channel Service Unit used to connect T1 data terminal equipment (DTE) such as a PBX, switch or channel bank to T1 facilities. Capable of interfacing to both B8ZS or AMI circuits, the T1 ESF CSU can convert signal formats or line code to integrate older equipment. The ESF CSU is designed to provide alarms, loopbacks, signal regeneration, line build-out, and surge protection, while maintaining 1s density for the DTE and T1 network.