The 1-port serial HWIC (HWIC-1T) and the 2-port serial HWIC (HWIC-2T) provide an EIA/TIA-232, EIA/TIA-449, V.35, X.21, data terminal equipment/data communications equipment (DTE/DCE) interface, EIA-530 DTE interface, or nonreturn to zero/nonreturn to zero inverted (NRZ/NRZI) serial interface to a Cisco modular router.