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ceivers, it is determined by the percentage of good
data messages received over a certain period.
When the home repeater signal strength drops
below the threshold, the status channel of that locality
is then monitored (see Section 4.6). If its signal
strength is also below the threshold, the subscriber
unit then begins searching for another locality by
checking the status repeater of other programmed
localities. If one is located with a signal above the
programmed threshold, it will attempt to register on
the locality. If no suitable status repeaters could be
located, the programmed home repeaters are moni-
tored.
When a new locality is located, the subscriber
unit registers on the locality by sending messages indi-
cating its unique ID code and the home channel it will
monitor. The system then knows the location of that
subscriber unit and will automatically route unique ID
calls to the new locality.
Automatic locality search can also be automati-
cally initiated if two consecutive unsuccessful access
attempts are made. With mobile transceivers, this
feature is always enabled, and with portable trans-
ceivers, it can be enabled or disabled by programming.
When a mobile subscriber unit is no longer in
service (power is turned off), a de-registration
message is automatically sent if possible. This
prevents the system from wasting resources trying to
reach out-of-service units. Power is automatically held
on until this message is sent. De-registration is
currently not available with portable subscriber units.
4.7.9 NEW CHANNEL UPDATES
New subscriber units are initially programmed
with the channel numbers of all repeaters at each
locality. These are then the channels that can be
accessed when placing and receiving calls on that
locality. If new channels are later added, the
subscriber units can be updated with the new chan-
nels over the air. This eliminates the need to bring
subscriber units back in for reprogramming. Refer to
Section 2.9.4 for more information.
4-9
LTR-NET OVERVIEW
April 1999
Part No. 001-9800-600
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