Beginning at the bottom of page 26 of the pdf owner's manual:
"open and closed modes
You can set your scanner to change the way it receives
signals. These settings, called open mode and closed mode,
affect how the scanner receives signals from communications
systems that use some type of closed squelch (such as
Motorola, EDACS, and LTR systems).
In open mode, you hear all active talk groups except those
you specifi cally exclude, making it easy to hear everything
going on. In closed mode, you hear only those talk groups
you specify. This makes it easy to listen only to talk groups
you are interested in and exclude others.
When you select a system voice channel manually, any
transmission opens squelch, regardless of the current
mode.
When no ID code is programmed into the scanner, it
receives the signal in MO, ED, or LT mode. In open mode,
the scanner stops on any transmission. If the ID is stored,
the text tag appears on the display. Otherwise, the talk
group ID appears on the display. In closed mode, the
scanner only stops on a transmission if the ID is stored.
You can set each of the scanner’s channel storage banks to
open or closed mode.
In open mode, the scanner scans signals transmitted in all
systems. The scanner stops on any ID code and only uses
the ID list to look up ID text tags.
In closed mode, the scanner stops only on signals that have
an ID code which is found in the ID list for the bank. Also, the
scanner scans signals transmitted only under the following
conditions:
• When the signals are in the FM, CT, or DC mode.
• When the signals are in the MO, ED, or LT mode and the
signal’s ID code matches the programmed ID code
You can also select the user or talk groups you want the
scanner to receive in closed mode.
When you set a channel storage bank to open mode, +
appears under the bank’s number while scanning. When you
set a channel storage bank to closed mode, - appears under
the channel storage bank’s number while scanning. OPEN
or CLOSED appears while the scanner is in manual mode or
while the scanner is receiving a signal during scanning. See
“Changing the Open/Closed Mode” for more information
about setting the open and closed modes."
