Philips LBB 1330, Инструкция по эксплуатации

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5. SM40 MODULES
5-35
5
5.9.2 Automatic Noise Dependent Audio Signal Processing (ANDAP)
Automatic Volume Control Card LBB 1359 & Signal Processing Card LBB 1358
In increasing ambient noise situations speech inteligibility of a call can be maintained by additional
amplification of only the higher frequency spectrum (1-4 kHz) without using additional booster power.
The AVC card LBB 1359/21 with two channels (control range of 21 dB) should be used together with the
SPC card LBB 1358/00.
Adjustment procedure for Automatic Processing (actual situation):
1. Check that jumpers J1 and J5 (0 dB bypass) are connected. Check that jumpers J2 and J6 (control path)
are removed. Turn the SENSE GAIN and the BLOCKING potentiometer fully clockwise (min.).
2. Check the quality and loudness of a regular call in the relevant AVC controlled loud speaker zone. This is
the not processed call level which should at least be at a Comfortable Listening Level (CLL) of
80 dB (SPL) peak-level. Ensure that the listening area is quiet i.e the ambient noise level is lower than
60 dB (SPL).
3. Check the connection of the ambient noise sensing microphone in the relevant loudspeaker zone is
connected to the sense input of the AVC channel. Turn the SENSE GAIN potentiometer fully anti-
clockwise (maximum). Turn the blocking potentiometer fully clock-wise (short). Produce a pink noise
signal at the input of the AVC channel. To produce a pink noise signal activate test signal 27 from the
SM40 Signal Generator Card (SGC). Measure the pink noise signal in the area of the relevant
loudspeaker zone. Adjust the disturbing LS-noise level to the level specified as the highest ambient noise
level - for example 80 dB (SPL). Adjust the SENSE GAIN so that DC voltage on J3 and J7 is 5V
maximum. Replace jumper J2 and J6.
4. The signal processing card (SPC) alters the frequency response of a call, and should be set for all three
frequencies on maximum gain (anti- clockwise) and minimum Q (clockwise). In addition the Bass-cut
should be set to maximum attenuation (anti-clockwise).
5. Connect the SPC to the AVC’s interconnection (check for the correct polarity). Produce a constant audio
signal (>10 mV) at the sense input to guarantee that the AVC is set at maximum gain (DC=5V on J3 and
J7. Adjust the max. processing (a lift of 10 - 15 dB around 2 kHz) with the MAX. CALL GAIN
potentiometer. For this alignment use the NEUTRIK response plotter or similar plotter.
6. Turn the sample BLOCKING potentiometer to its mid position. This allows approximately two seconds
of silence before the AVC sensing alters the call output level. Turning the BLOCKING potentiometer
further in a clockwise direction, shortens this time, thus allowing readjustment of the level during shorter
call pauses. If the reverberation time in the loudspeaker zone is too long, the sensing microphone could
sense the reverberation of the call as ambient noise. This will cause the AVC to compensate for its own
calls, therefore causing a malfunction. (i.e switches always to maximum call level).
7. Carry out a listening test in order to check that it functions correctly.