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Uses of unique ID codes include registering and
de-registering on a locality, unit identification, airtime
billing, and unique ID calls (see "Unique ID Calls" in
Section 6.5.2). A call can also be made to individual
subscriber units using a group call if the group is
assigned to only one subscriber unit.
A temporary unique ID code can also be assigned
over-the-air. This may be required to allow a full
roaming subscriber unit to access a locality that is not
part of its network. Temporary unique ID codes are
keyed to the ESN of the subscriber unit (see next
section). A roaming subscriber unit may also request a
temporary unique ID code. If no response is received
from the system after two temporary ID requests, it is
interpreted as a denied access and the mobile then
selects another locality.
NOTE: The preceding feature has not yet been
implemented.
6.7.2 ELECTRONIC SERIAL NUMBER (ESN)
Each subscriber unit, both mobile and portable, is
given an electronic serial number at the factory. No
two LTR-Net subscriber units should ever have the
same ESN. This is a 32-bit number with the first 7 bits
reserved for the manufacturer code and the other 25
for the serial number. This allows for up to 128 manu-
facturers and over 33.5 million serial numbers per
manufacturer. The ESN can be interrogated over the
air as described next.
6.7.3 ESN AND UNIQUE ID REQUESTS
The system operator can request the Electronic
Serial Number (see preceding section) or unique ID
(see Section 6.7.1) that is programmed in a subscriber
unit. If the ESN is desired, the unique ID code of the
subscriber unit is specified, and vice versa. The
subscriber unit then responds with the requested
information.
6.7.4 INTERROGATE
A system manager can interrogate any subscriber
unit in the field to determine if it is in service. The unit
is selected by specifying its unique ID code. If it is in
service, it automatically responds with an acknowl-
edge message, and this will be indicated on the system
manager's screen.
6.7.5 KILL AND SLEEP
If a subscriber unit has been lost or stolen or is
being used to interfere with communications, it can be
permanently disabled by the kill command or tempo-
rarily disabled by the Sleep command. If the Kill
command is sent, the unit responds indicating that it
has received the message and then it permanently
disables itself. It must then be brought back in for
reprogramming to make it functional again. If the
sleep command is sent instead, the transceiver is
disabled until the Interrogate command is sent. Refer
to Section 2.9.6 for more information.
6.7.6 AUTO-REGISTRATION AND
DE-REGISTRATION
LTR-Net subscriber units are programmed with
the locality information of all localities they can roam
into. This includes the channel number or frequency of
the status repeater of each locality. The repeaters that
are active at each site can then be determined by auto-
matic channel update messages (see Section 6.7.7).
Roaming must be enabled and an LTR-Net system
selected for roaming to occur (it is not necessary to
enable scanning).
Normally, a subscriber unit monitors its home
channel for incoming call and free channel informa-
tion. When moving out of range of a locality, the
signal from the home repeater decreases below a
programmable threshold level. With all transceivers
except the 8170 portable, this threshold level is deter-
mined by squelch levels, and with the 8170, it is deter-
mined 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 6.6). 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 monitored.
6-8
LTR-NET OVERVIEW
November 2001
Part No. 001-7240-001
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