This specifies the center frequency, in kHz, for the single-carrier modulation profile K, defining where in the spectrum this line's single carrier signal is centered, analogous to tuning a radio to a specific frequency rather than spreading across many discrete tones like DMT does. It matters for coordinating spectrum use among multiple SCM lines or avoiding interference with specific known noise sources at particular frequencies, since shifting the center frequency moves the entire signal's occupied band. Two SCM lines deployed in the same binder might be deliberately assigned different center frequencies here specifically to reduce mutual crosstalk between them.