This is a read-only integer, in dB, reporting the combined Echo Return Loss, cancellation-loss enhancement, and nonlinear processing loss currently achieved by the echo canceller on this call leg, with -1 meaning the level can't be determined or level detection is disabled. An admin monitors this to gauge how effectively echo is being suppressed on a live call, since a low value suggests weak overall echo cancellation. For example, persistent low readings here on a specific voice port might lead an admin to suspect a hardware or line-impedance problem on that port rather than a software configuration issue.