User's Manual

Galaxy Tracking Systems, L.L.C. Technical Documentation - VTU
Once the VTU has been initialized the first time, it will be able to reinitialize within a
minute unless it has been disconnected from vehicle battery power for a long period of
time (greater than a week).
8.2 VTU Operating Modes
The VTU operates in one of two modes, IN SERVICE or OUT OF SERVICE. In either
mode, the VTU receives commands over the UHF radio link from the command center.
The VTU confirms each command by responding with either an IN SERVICE or OUT
OF SERVICE message.
Commanded settings and status are maintained through power outages.
8.2.1 OUT OF SERVICE Operating Mode
The VTU is factory configured to begin life in the OUT OF SERVICE operating mode.
OUT OF SERVICE is a standby mode that is also used to verify unit communications.
While in this mode, the VTU will transmit an OUT OF SERVICE response to all
commands except the IN SERVICE command.
When OUT OF SERVICE, all in-vehicle alarms are disabled, (see SELF-
ACTIVATION).
8.2.1.1 OUT OF SERVICE Operating Mode Commands
The commands available with OUT OF SERVICE follow.
IN SERVICE Command
Upon receipt of an IN SERVICE command, the VTU will change operating mode to IN
SERVICE and transmit an IN SERVICE message to report the change in mode. The
VTU is set operational by this command and can begin to report position, time, status and
on-board alarms.
8.2.2 IN SERVICE Operating Mode
When commanded IN SERVICE, the VTU will respond with a single IN SERVICE
message at the exact time indicated in the command packet. While IN SERVICE, the
VTU transmits an IN SERVICE message in response to all commands. The VTU will
also transmit an IN SERVICE message in response to alarms activated by the vehicle
operator (e.g., SOS) or events (e.g., unauthorized movement).
8.2.2.1IN SERVICE Operating Mode Commands
The commands available with IN SERVICE follow.
OUT OF SERVICE
The VTU will change operating mode to OUT OF SERVICE and transmit an OUT OF
SERVICE message to report the change in mode. On-board alarms are disabled. All
subsequent commands (except IN SERVICE) are answered with an OUT OF SERVICE
message.
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