In a telecommunications link or line facility, interference, from any source, that degrades performance. Note 1: Line noise is usually measured as a signal-to-noise ratio and as a set parameter used by engineers to determine the operating range of the system. Note 2: In analog lines, noise is usually measured in dbrnc (dB relative to -90 dBm, with C-message weighting. ) Note 3: In digital lines, noise is usually measured as a function of the number of errored bits per second or errors in the digital data stream. In digital systems with signal buffers, these errors may be linked to alarms, and to circuitry that enables the signal to be recovered to acceptable degree.