Uniden UH5000 Owner's Manual page 11

Operation
oF(off) - squelch open.
1 - max sensitivity (min squelch)
5 - med sensitivity (med squelch)
9 - min sensitivity (max/tight squelch)
You must select a channel which is not in use before setting
the SQUELCH control. (see p.12 for "Selecting a Channel").
NOTE
UNIDEN UH5000
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.
11
UHF CB Transceiver