Uniden Bearcat PC687 Owner's Manual page 7

Automatic Noise Limiter (ANL) features. NB reduces external
noise and ANL reduces background noise from the car engine
and other sources. OFF turns off both the NB and ANL features.
4. BRT/DIM switch: Adjust backlight brightness.
5. CH9/OFF switch: Move the switch to select emergency channel 9
or turn to off for normal CB operation.
All channels except Channel 9 may be used for normal communication.
The FCC reserves Channel 9 for emergencies involving the immediate
safety of individuals or protection of property. Use Channel 9 to render
assistance to a motorist.
6. HIGH CUT/OFF switch: Select HIGH CUT to apply the High Cut
filter.
7. RX/TX LED: Indicates whether the radio is transmitting (red) or
receiving (yellow-green).
8. CH9 LED: Indicates that emergency channel 9 is selected.
9. Channel Indicator: Displays the channel currently in use.
10. 6-Pin Microphone Jack: Connects the radio to the detachable
microphone (included).
11. Channel Selector knob: Turn this knob to select CB or Weather
channels.
12. RF GAIN inner knob: Turn the inner knob to reduce interference
in strong signal areas.
13. MIC GAIN outer knob: Turn the outer knob to adjust the
microphone sensitivity.
14. VOL inner knob: Turn the inner knob to turn the radio on and off
and to adjust the volume.
15. SQUELCH outer knob: Turn the outer knob to reduce background
noise when there is no incoming signal.
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