This read-only string reports the robbed-bit signaling pattern the modem has detected on the T1 or E1 style line, a signaling technique that steals low-order bits for signaling purposes, or reports 0 if none is detected. Admins check this when a call's data quality is degraded, since unexpected robbed-bit signaling on what should be a clear-channel connection can reduce usable bandwidth and affect modulation. For example, a modem unexpectedly reporting a robbed-bit pattern on a line expected to be clear-channel would prompt an admin to investigate the carrier's line provisioning.