Audiovox FR240T Owner's Manual page 10

Continuous Tone Coded Squelch System (CTCSS)
This feature allows you to ignore transmissions from other units
that are using the same channel. One of 38 privacy codes may
be selected. The same code must also be selected on those
transceivers with which you desire to communicate. Keep in
mind, however, that this feature does not prevent others from
listening to your transmissions.
To Select a CTCSS Code
Press the function select button twice or until the small digits on
the right flash on the display. Use the up and down buttons to
select the desired squelch code number. After 5 seconds, the
unit will return to the standby mode. The CTCSS squelch code
will be applied only to the currently selected channel. To disable
the CTCSS, and allow the transceiver to receive all messages
on a particular channel select "00" as the code.
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