Context
Display Gain controls the "amount" of echo that is displayed, in other words the "strength" or "intensity" of the echo presentation. The function thus increases or decreases the presentation of the echo colours. Use this setting together with Gain to adjust the sensitivity of the ST90 system.
For all practical purposes, adjusting Display Gain has the same effect as adjusting Gain. Adjust the Display Gain so that you can see the targets without too much noise and reverberation. The chosen setting is a matter of personal preferences.