This read-write INTEGER provisions the assumed Echo Return Loss, i.e. the dB level of echo the DSPs are expected to cancel, choosing among zero, three, six dB, or worst-case. This setting tunes the echo canceler's expectations to match the actual acoustic/electrical echo characteristics of the connected circuit, affecting how effectively echo gets removed. For example, on a circuit known to have particularly poor return loss, an admin would set vismERL to worstdb so the canceler is configured to handle the harsher echo condition.