ZETRON 4000 Series, Руководство по установке

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185
Microphone Adjustments
Microphone Adjustments
An automatic gain control (AGC) limits the maximum amount of audio that may pass
through a console. If not properly adjusted, AGC circuits can amplify background noise
when the operator is not speaking. Proper adjustment and microphone practices will
eliminate background noise from transmitted audio.

To adjust the microphone levels
1. For a Model 4018, open the case to access the potentiometers. See Model 4018
microphone adjustments in Figure 35 . For Models 4116B, 4118, and 4217B, the
adjustments are accessible at the rear of the console.
2. Use Table 80 to find the appropriate potentiometer for adjusting your microphone.
Table 80: Microphone Adjustments
3. While transmitting, speak into the microphone at a normal voice level and distance
from the microphone.
4. Turn the appropriate MIC potentiometer until the background noise is removed
without reducing voice amplitude.
5. Verify audio quality by monitoring the transmitted signal or by observing the level
meter under the time display. Optimum performance is achieved when the operator
speaks at the level and distance for which the console was adjusted.
6. If the PTT handset with cradle option was installed, the ear audio level is adjusted
by R7. This is set at the factory and probably needs no adjustment.

To perform precise microphone level adjustments
1. Begin transmitting a constant 1kHz alert tone from the console.
2. Adjust the console’s Alert Tone potentiometer to ½ turn past knee of compression
observable at the CIC mic test point.
3. Adjust the CIC mic for 0.25 Vrms (-10 dBm) at the mic test point.
4. Repeat steps 2 and 3 for each console.
Model Level Part Label
4018
Handset/headset microphone R68 E
Desktop microphone R70 D
Gooseneck microphone R69 GN
4116B, 4118, 4217B
Handset/headset microphone – H-MIC
Gooseneck/desktop microphone – D-MIC
Note
A desktop or gooseneck microphone connects to the D mic input of
the AUX AUDIO connector.