Uniden UH7700NB Owner's Manual page 11

Operation
oF(off) - squelch open.
  PD[ VHQVLWLYLW\ PLQ VTXHOFK
  PHG VHQVLWLYLW\ PHG VTXHOFK
 PLQ VHQVLWLYLW\ PD[WLJKW VTXHOFK
You must select a channel which is not in use before setting
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NOTE
UNIDEN UH7700NB
Think of the squelch control as a
gate. If you increase the squelch level
to maximum it raises the 'Squelch
gate' so only the strongest signals get
through.
If you decrease the squelch level to
minimum it lowers the 'Squelch Gate'
to the extent that weak signals can
get through.
If unwanted weak and noisy signals
are getting through increase the
squelch level ('Squelch Gate') to a
medium level. Now only medium
and strong signals get through.

UHF CB Transceiver