The Second Generation (2nd GEN) Nx56/64 V.35 option module is one of the option modules available for use with the following ADTRAN equipment: TSU 100 (part number 1200052L1), TSU 600 (part number 1200076L1), TSU 120 (part number 1200129L1), HSU 100 (part number 1200097L1), HSU 600 (part number 1200098L1). This manual provides an overview of the module with installation and operation instructions.