About The Equipment; Functioning (Operating Principle) - Bosch Security Systems Plena LBB 1968 Installations- Und Bedienungshandbuch

Plena Feedback Suppressor | Installation and Operating Manual |
1

About the equipment

1. 1

Functioning (operating principle)

signal
level
In 1
pin 4,5 mic/line
In 2
figure 1. 1 : Block diagram
Feedback suppression
The Plena Feedback Suppressor uses a powerful DSP with a revolutionary patented algorithm to suppress acoustic
feedback. It eliminates feedback by actively filtering the room reverb that leads to feedback out of the signal, using
an echo cancellation and de-reverberation algorithm. By adding masked (inaudible) noise to the output signal
(Mode 2) or by just shifting the frequency of the output signal by 5 Hz (Mode 1) the Plena Feedback Suppressor is
able to detect the reverb component of the signal and to remove it before feedback occurs, leaving the original
signal intact.
Auto Mix function
In addition to its feedback suppression function, the Plena Feedback Suppressor also features a built-in automatic
mixer for the two microphone inputs. In many situations two microphones are used to better capture the voice of a
moving speaker, like on a rostrum, pulpit or a conference table, but often this increases the risk of acoustic feedback.
The automatic mixer of the Plena Feedback Suppressor, however, automatically reduces the gain of the microphone
with the lowest signal input and increases the gain of the microphone with the highest signal input. This way it
'tracks' the moving speaker for optimum speech intelligibility, and the maximum feedback margin is maintained by
keeping the summed gain constant. Even if the feedback processor is switched to bypass this automatic mixer is still
operating.
Bosch Security Systems | 2003-11 | 9922 141 81681
A
+
D DSP
C
peak
About the equipment
D
A
C
pin 4,5
signal
bypass
auto mix
fast/accurate
calibrate
mode 1/mode 2
bass lift
en | 7
line level out
mic level out
line level out