User Manual camera 990, 880, 770

TANDBERG Videoconferencing SystemAdvanced use

Automatic Gain Control (AGC) Settings

Select ‘On’ to allow automatic adjustments (Automatic Gain Control) of audio levels. When ‘On’, the AGC

maintains the audio signal level at a fixed value by attenuating strong signals and amplifying weak signals. Very

weak signals, i.e. noise alone, will not be amplified.

Example: In most conferences, the participants will speak at different levels, and be at different distances from the

microphones. As a result, some of the participants would be harder to hear than others. The AGC corrects this

problem by automatically increasing the microphone levels when “quiet” or “distant” people speak, and by

decreasing the microphone levels when “louder” people speak.

When applying a weak signal in the presence of strong background noise, the AGC might amplify the background

noise as well as the signal. Therefore, in noisy environments, it is advisable to turn the AGC off.

Tips for improving the echo canceller performance:

• Place all microphones as far as possible from the loudspeaker. Minimum loudspeaker-microphone distance

should be 1 meter.

• Place all microphones as close as possible to the persons speaking. By using several microphones, the ratio

distance loudspeaker-to-mic/mic-to-speaker can be increased. Increasing this ratio improves the echo canceller

performance. Avoid distances above two meters from any participant to his/her closest microphone. If

necessary, use several microphones. Also avoid placing microphones less than one meter from any person.

• Place all microphones as far as possible from noise sources.

• Reduce the volume setting. Ensure that the loudspeaker does not distort the audio.

TO ENSURE CORRECT BEHAVIOUR OF THE AGC, IT IS CRUCIAL THAT THE LEVELS ON THE INPUT CONNECTORS ARE ADJUSTED CORRECTLY

USING THE AUDIO INPUT LEVEL SETTINGS. THE AGC WILL NOT COMPENSATE FOR SEVERE MISADJUSTMENT OF INPUT LEVELS.

NOTE