LTR-NET OVERVIEW
4-8
April 1999
Part No. 001-9800-600
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 three requests, access was
denied and the unit must select another locality.
NOTE: The preceding feature has not yet been
implemented.
4.7.2 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.
4.7.3 ESN AND UNIQUE ID REQUESTS
The system operator can request the Electronic
Serial Number (see preceding section) or unique ID
(see Section 4.7.1) 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.
4.7.4 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.
4.7.5 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 2.9.5 for more information.
4.7.6 OVER-THE-AIR REPROGRAMMING
Any system and group position of a subscriber
unit can be reprogrammed over the air. Up to 128
system selections and 128 group selections are
allowed. In addition, group alpha tags of up to 16
characters can be reprogrammed if applicable. The
subscriber unit to be reprogrammed is selected by
specifying its unique ID code. One use of this feature
is to allow a subscriber unit to place and receive calls
for which it was not originally programmed.
4.7.7 MOVE TO SPECIFIC SYSTEM/GROUP
The system/group currently selected by a
subscriber unit can also be dynamically changed over
the air. As with reprogramming, the subscriber unit is
selected by specifying its unique ID code. When the
command is received, the unit automatically changes
to the specified system/group. This function may be
used, for example, to ensure that the correct system/
group is selected to receive an important message.
4.7.8 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 status and home channels and
the channel frequencies of the locality repeaters.
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 mobile trans-
ceivers, this threshold level is determined by squelch
levels (see Section 2.9.3), and with portable trans-
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