This counter tracks the number of ATM cells whose header error control (HEC) field detected and corrected a single-bit error. Admins watch this as an early warning sign of line quality degradation, since correctable errors often precede uncorrectable ones as a signal continues to degrade. A steadily rising corrected HEC count, even with zero uncorrected errors, would prompt an admin to investigate the physical link before it worsens into cell loss.