Earphone Connection; Dial - Tuning Control / Selector; Squelch Control - AOR AR8000 Operating Manual

5-2 EAR - Earphone / speaker connection
This 3.5mm mono socket permits connection to an external earphone, headset
or speaker of 8 OHM impedance or greater. When this earphone socket is
used, the internal speaker will be automatically disconnected.

5-3 DIAL - tuning control / selector

The DIAL control is prominently located on the top of the
cabinet for ease of use. This control changes the received
frequency up and down in whatever step increment is selected and operates as
a "selector" when entering certain data though menus. This type of rotary
control is often referred to as the "VFO".
Being a mechanical device, it is not uncommon for operations to be
occasionally missed and this does not constitute a fault (unless excessive).
5-4 SQ - squelch control
The squelch control is used to eliminate unwanted background
noise when monitoring a normally inactive frequency and is
used by the AR8000 microprocessor to determine when a channel is "active"
(busy). The receiver cannot scan or search when the background noise is
present.
The squelch control requires careful setting to achieve optimum operating
performance. Rotate the control clockwise until the background noise just
disappears (threshold), this is the most sensitive setting of the control. In
practice the control is usually rotated a little further clockwise beyond the
threshold point to prevent the receiver from stopping on noise or very weak and
unreadable signals.
If the control is rotated too far clockwise then weaker signals will be totally lost
and only local strong signals will be heard.
When the squelch control is rotated anticlockwise so that background noise is
audible, the squelch is referred to as being "OPEN". In a similar manner, when
the squelch control is rotated clockwise so that the background noise is muted,
the squelch is referred to as being "CLOSED".
The squelch is not usually used when listening to short wave transmissions
due to the relatively high short wave background noise levels nor in WFM
mode. The usual setting for the control when listening to short wave or WFM
is fully anticlockwise (squelch open).
Note: Even when the squelch is fully CLOSED a low level background noise
may still be audible. This is because the receiver's audio amplifier circuit is
permanently operational in order to provide fast search/scan rates and an
efficient squelch opening characteristic. This phenomenon is common with
other hand-held receivers on the market today.