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Bosch Security Systems | 2011-02
Praesideo 3.5 | Installation and User Instructions | 9 | System Configuration en | 405
• Make sure that all loudspeakers are connected to the
system, set at the correct power level, are aimed (if
necessary) and are working.
• Adjust the nominal output level of all audio outputs
in the zone to the level required to have the correct
speech intelligibility at maximum ambient noise
level.
• Make sure that the the audio delay setting of the
applicable power amplifier outputs is set to a value
< 2 s. After the calibration the audio delay can be set
back to the correct value. Very long delay settings,
e.g. for tunnel applications, may cause wrong
calibration results.
Proceed as follows to configure AVC:
1 Go to the AVC settings category of the Zone
Configuration page. A screen similar to the one in
figure 49.1 appears in the main frame of the web
interface.
2 Put a check mark in the Enabled checkbox to enable
AVC for calls. The ambient noise level that is used to
adjust the volume of the call, is measured just before
the start of the call.
3 Normally the AVC works for calls. When the AVC
should also work for BGM, put a checkmark in the
BGM box. The ambient noise level that is used to
adjust the volume of the BGM, is measured
continuously.
4 By default AVC also works for the emergency calls,
but if Control Emergency is disabled then emergency
calls will be broadcast at maximum (configured)
level.
5 Choose the audio input to which the sensing
microphone is connected from the Sense input
dropdown list.
6 Select the call margin from the Call margin
dropdown list. This is the threshold level of the AVC
function. When the ambient noise level is below the
call level by more than the call margin, the AVC
starts attenuating the call.
7 Select the release time from the Release time
dropdown list. This is the time between the end of
the call and the start of the ambient noise
measurement.
figure 49.1: AVC settings
Note
The AVC settings only apply to the audio
outputs of power amplifiers. It is not possible to
apply AVC to the audio outputs of basic
amplifiers or other units.
Note
When AVC is enabled for BGM, make sure that
the sensing microphone is not near the
loudspeakers. If the sensing microphone is near
the loudspeakers, the BGM itself is seen as
ambient noise and the volume level of the BGM
will increase to the maximum volume level
(feedback).
Note
A value of 12 dB is a practical value. A higher
value results in a bigger difference between the
volume levels of the calls and the ambient noise.
However, this requires more (or bigger)
loudspeakers and power amplifiers to reach the
high call volume when the volume level of the
ambient noise is high.
Note
A value of 6 s is a practical value. A short
release time combined with a long reverberation
time can cause a high call volume level.