User's Manual

Draft
December 2006 5300 ES Series Mobile Radio Operating Manual -11
The priority channel sampling frequency is determined by the programmed Priority
Lookback Time A (see description which follows). For example, if 2.0 seconds is
programmed, the priority channel is sampled every 2.0 seconds when listening to a
message on a non-priority channel. When not listening to a message, the priority channels
are scanned in the normal scan sequence. With dual priority, the first and second priority
channels are alternately sampled at the Loopback Time.
Priority channel sampling occurs only with standard conventional scanning. It does not
occur with radio-wide scanning, when listening to any type of SMARTNET/SmartZone/
P25 conventional or trunked call, encrypted call, or when transmitting. A series of “ticks”
may be heard when the priority channel is sampled while listening to a message on some
other conventional channel.
The priority sampling times are programmed by the following parameters:
Lookback Time A - This time determines how often the priority channel is checked for
activity. Times of 0.25-4.00 seconds in 0.25-second steps can be programmed.
Lookback Time B - This time determines how often the priority channel is checked
once an incorrect Call Guard (CTCSS/DCS) or NAC code is detected. Since it takes
much longer to detect an incorrect Call Guard signal than a carrier, this time should be
relatively long to prevent the interruptions from making a message difficult to
understand. Times of 0.5-8.0 seconds can be programmed in 0.5-second steps.
5.10.3.1 Changing The Priority Channel
If a fixed priority channel is associated with the current scan list, it can be changed to
another channel if the PRI ED option switch is programmed. With dual priority, this
changes only the first priority channel. To change both priority channels, use the Scan List
Edit function described in
Section 4.12.1. Proceed as follows to change a priority channel
using the PRI ED option switch:
1 Make sure that both priority and radio wide scanning are off (the rotating icon is not
indicated in the right status display).
2 Select the channel that you want to be the priority channel using the Select switch in the
normal manner. If the channel is in a different zone, also select the appropriate zone.
3 Press the PRI ED option switch and “Priority” is briefly displayed to indicate that the
selected channel is now the priority channel. Other indications that may occur are as
follows:
• If “No Priority” is displayed, priority sampling may not be enabled on the scan list.
• If “Sel Chan” is displayed, the priority channel is always the selected channel and
cannot be changed.
• If no indication displayed, the scan list may not be user editable or the channel may
not be in the scan list.