bitsPortLineType is a read-write setting that determines whether a T1/E1 BITS port operates in T1, E1, or 2048kHz mode. An administrator must set this to match the timing signal actually wired into the port, since selecting the wrong line type will make the port unable to correctly frame or interpret the incoming reference clock. For example, a site fed by a European E1-based timing source would set this object to E1 rather than leaving it at a T1 default, which would cause the BITS-IN port to fail to lock onto the signal.