bitsPortSaBitDesignation is a read-write setting that selects which E1 Sa bit (with a default of Sa4) is used to carry the Synchronization Status Message on this BITS port; it is forced to 'none' when the line type is T1 or 2048kHz since only E1 framing carries Sa bits. An administrator configuring E1-based SSM signaling must align this with what the far-end timing source actually uses, or the quality-level information embedded in the Sa bit will not be read correctly. For example, an E1 BITS-IN port receiving SSM on Sa bit 4 from an upstream PRC would leave this at its Sa4 default rather than picking another Sa bit position.