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Level Adjustments
provided with the 4010 when shipped to facilitate test point access. See Model 4010 Dual
Channel Card Layout on page 103 for the location of P1. The P1 test points are:
On a four-wire channel, use the 4W-RX adjustment. On a two-wire channel, use the
2W-RX adjustment. Start with the adjustment fully counterclockwise (25 turns) and then
turn the adjustment clockwise while observing the voltage measurement. Adjust for the
knee of compression by stopping when the measurement stops increasing, which will be at
about 0.24 Vrms (0.7 Vpp or -10 dBm).
In most applications, completely turn off either the 2-wire or 4-wire pot (whichever is not
being used to carry audio).
Microphone Adjustments
The microphone audio inputs of the Dispatch Console are run through an automatic-gain-
control (AGC) which limits the maximum amount of audio that may pass through it.
However, AGC circuits, if not properly adjusted, can cause background noise to be
amplified when the operator is not speaking. Proper adjustment and microphone practices
will eliminate background noise from the transmitted audio.
The microphone levels are adjusted by speaking into the console microphone (while
transmitting) at a normal voice level and distance from the microphone, and turning the
adjustment until the background noise level is removed without reducing the amplitude of
the voice. This can be verified both by monitoring the transmitted signal, and by observing
the bar-graph level meter under the console time display. Optimum performance is
achieved when all dispatchers speak at the level and distance for which the console was
initially adjusted.
P1-1 Analog ground
P1-2 CHB receive (RXB)
P1-3 CHB transmit (TXB)
P1-4 CHA receive (RXA)
P1-5 CHA transmit (TXA)
Adjustment Part Label
Handset/Headset Microphone R68 E
Desk-Top Microphone R70 D
Gooseneck Microphone R69 GN
PTT Handset with Cradle R7 E
Tip Gooseneck and desk microphones are designed to have the mouth
within a few inches of the microphone element. Otherwise, voice
quality is impacted and there is increased pickup of background
noise.
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